Cathodic Performances of MnO2 Induced C/Ni Foam Electrode for H2O2

doi:10.21203/rs.3.rs-3395584/v1

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Cathodic Performances of MnO2 Induced C/Ni Foam Electrode for H2O2

https://doi.org/10.21203/rs.3.rs-3395584/v1

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MnO₂ has been regarded as the key active species for the reduction of H₂O₂, and the catalytic performances of electrodes and the open circuit potential are related to the MnO₂ preparation. However, there is limited understanding of how the operation para-meters affect the MnO₂ preparation and utilization. The sol-gel method was used to prepare the MnO₂ and a suitable preparation process was determined via the orthogonal and single-factor experiments. The optimal preparation conditions were: n (citric acid): n (manganese acetate) = 0.5:1, initial concentration of reactant C₀ = 0.1M, pH ≈ 6, temperature of reaction was about 60℃. The X-ray spectroscopy and cyclic voltammetry confirm that MnO₂ by sol-gel method was termed as mixed crystal of α-MnO₂ and γ-MnO₂. Excessive H₂O₂ was detrimental to catalytic ability of electrode because of the self-decomposition reaction of H₂O₂. Operation conditions affect the polarizability, which was an important indicator of the catalytic performance of electrodes. In this study, a new C/MnO₂/Ni foam cathode was constructed by combining MnO₂ with C(carbon), and the catalytic activity of the electrode was correlated with the content of MnO₂ and the concentration of H₂O₂, which provided a strategy for the design and operation optimization of MnO₂ cathode catalyst. The results show that the optimal concentration of H₂O₂ is 0.3M, and the optimal mass fraction of MnO₂ in the electrode is 40%.

Manganese dioxide

Hydrogen peroxide

sol-gel method

electrocatalytic performances

catalytic conditions

In recent years, researchers have become increasingly interested in the metal semi-fuel cells that have been considered as the new option of sustainable energy conversion and storage devices [1, 2]. The hydrogen peroxide (H₂O₂) has some advantages, such as faster reduction kinetics than oxygen, easy storage and handling [3–5]. The metal semi-fuel cell with H₂O₂ as the cathode reaction material has been proposed as a potential option for space and underwater power source [6–9].

The majority of studies have been focused on effects of precious metals and their alloys as cathode catalysts on electrochemical reaction rate of H₂O₂ [10–16]. However, the performances of the commonly used precious metal catalyst are excellent, it is considered too expensive to be commercially attractive [17]. The usefulness of manganese dioxide (MnO₂) has been examined as a cathode catalyst for metal-semi-fuel cells [18.19]. MnO₂ has been extensively applied as a superior catalyst of H₂O₂ in many fields due to its low price, good environmental compatibility, low toxicity, and excellent catalytic performance [20–26]. The electrode based on MnO₂ is a candidate metal-H₂O₂ semi-fuel cell cathode catalyst on account of its relatively wide working potential window (which can generally reach about 1.0V in aqueous solution) and good electrocatalytic activity [27–30].

However, one of the limitations of using sol-gel method to prepare MnO₂ came from the fact that the optimal experimental conditions for the gel precursor are still uncertain [31–34], which suggested that the preparation process of MnO₂ can be improved. Meanwhile, the reaction conditions (such as the mass fraction and structure of MnO₂ as well as the concentration of H₂O₂) have been summarized as important parameters of the catalytic process [35]. Nevertheless, the correlation between these important parameters and the catalytic effects of MnO₂ was still not clear [36–38].

Therefore, the purpose of the study is to examine the catalytic ability of MnO₂ to H₂O₂ under different conditions, and confirm the optimum experimental conditions. In the meantime, the process parameters of sol-gel method and the main components of MnO₂ were examined in this study.

2.1 Chemicals

The chemicals used in this study were the analytical grade and were used without further purification. Reagents (C₆H₈O₇ · 2H₂O, H₂O₂, KMnO₄, H₂SO₄) and Mn (CH₃COO)₂ · 2H₂O are purchased from Tianjin Hengxing Chemical Reagent Manufacturing Co., Ltd. and Harbin Xinda Chemical Plant, respectively. Nickel foam (Ni foam, SBET = 1.61 m² /g, surface density = 380 g/m², pore number = 110 ppi) was chosen as the substrate of electrode. The KOH solution as the electrolyte and the ammonia used to adjust the pH were provided by Tianda Chemical Reagent Factory of Dongli Distrin. Ultrapure water (18.2 MΩ · cm^− 1) was used for the preparation of aqueous solutions.

2.2 Preparation and characterization of MnO₂

In this study, MnO₂ samples were fabricated via the sol-gel process [31, 39]. Sol-gel method is widely used in many fields [40]. First, manganese acetate and citric acid were weighed and dissolved in an appropriate amount of ultrapure water to prepare a specified solution. Second, the manganese acetate solution and the citric acid solution are mixed according to a set molar ratio, and the ammonia solution is slowly added dropwise to adjust the pH of the solution. Then, the solution was heated and stirred in a thermostatic water bath until the light pink solution turned into a black wet gel that was moved to an oven to dry and dehydrate until the wet gel became a dry gel. Finally, the dry gel was pulverized and placed in a muffle furnace for firing to receive a black MnO₂ sample.

The crystal structure of manganese dioxide samples was characterized by powder X-ray diffraction (XRD, Rigaku Ultima IV) patterns which were recorded on a D/MAX-rB X-ray diffractometer with Cu Ka irradiation. the incident wavelength was λ = 0.15406nm, and the scanning range was 2θ = 0 ~ 100 °

The morphology and structure of manganese dioxide samples by sol-gel method were characterized by scanning electron microscope equipped with energy dispersive X-ray spectroscopy.

Grain size was calculated according to the following Scherrer equation [41]:

$$D=\text{K}{\lambda }/\left(\text{B} \text{c}\text{o}\text{s}\theta \right)$$

In this equation, D is the size of grain (nm), which represents the average thickness of the grains in the direction perpendicular to the hkl crystal plane, λ is the incident wavelength (nm), K is the Scherrer constant (0.89), B is the half-high width of the diffraction peak of the sample, which needs to be converted into radians (rad) in the calculation process, and θ is the Bragg diffraction angle in degrees.

2.3 Electrode preparation and electrochemical measurement

Prior to fabrication, the Ni foam (10 mm × 10 mm × 1.5 mm) was successively cleaned in 80 g/L H₂SO₄, and distilled water with ultrasonic.

First of all, the MnO₂ prepared by the sol-gel method was placed in a beaker at a designed ratio with carbon powder and PTFE, and an appropriate amount of ethanol was added and mixed uniformly. Subsequently, the mixture was heated in a constant temperature water bath at 80°C to demulsify the alcohol, and then fibrillate the PTFE until the mixture became agglomerates. Then, the agglomerated mixture was coated on the treated porous foamed Ni (10 mm x 10 mm) substrate, and dried in an oven at 105°C. Finally, a tablet machine was used to press the dried substrate into a sheet with a thickness of 0.2 mm more or less to prepare an experimental electrode.

To confirm the ability of MnO₂ to reduce hydrogen peroxide, the cyclic voltammetry was required. The electrochemical properties of the as-prepared electrode materials were performed using a CHI 604D electrochemical workstation with a three-electrode configuration. Cyclic voltammetry with scan rate of 20 mV · s^-1 were conducted in 6M KOH aqueous solution using Ag / AgCl electrode as the reference electrode, carbon rod as the counter electrode, and the C/MnO₂ as the working electrode. In addition, the scan range was set form − 1.5V to 0.6V during the cyclic voltammetry performance test.

2.4 Analytical methods and data analysis

There are many factors that affect the structure and properties of MnO₂ in the sol-gel process for preparing MnO₂, including the ratio of reactants, solution pH, solution concentration, reaction time and temperature, roasting time and temperature, and so on. After consulting relevant literature and conducting exploratory experiments, the pH of the reaction solution was initially determined to be 8.0. Orthogonal experiments were designed to investigate the effects of experimental conditions on product properties, and then the basic experimental process was determined. The parameter design for orthogonal experiments were summarized in Table 1. Subsequently, a single factor experiment was performed to analyze and discuss the influence and effect of the main influencing factors such as the ratio of reactants, solution pH, solution concentration, reaction time and temperature on the structure and electrochemical performance of the material.

Table 1

Parametric design of orthogonal experiments
Number	Initial reactant concentration /M	c(Citric acid) : c(Manganese acetate)	Water bath temperature /℃
1	0.1	0.4:1	60
2	0.1	0.5:1	70
3	0.1	0.6:1	80
4	0.5	0.4:1	70
5	0.5	0.5:1	80
6	0.5	0.6:1	60
7	1.0	0.4:1	80
8	1.0	0.5:1	60
9	1.0	0.6:1	70

In addition, the content of MnO₂ and total manganese in the samples were determined using the two-step continuous titration method, which includes the REDOX titration and the complexometric titration [42], the chemical reactions were shown as following:

MnO₂ + C₂O₄²⁻+4H⁺=Mn + 2CO₂ + 2H₂O (2)

5CO+2MnO+16H=2Mn+10CO + 8HO (3)

Mn²⁺+EDTA →Mn (EDTA)²⁺ (4)

In this work, experimental steps were designed based on chemical reaction principles.

For one thing, the content of manganese dioxide in the sample needs to be determined, a 150–170 mg of manganese dioxide samples and 0.33–0.35 g of Na₂C₂O₄ were accurately weighed into a 150-ml conical flask, 8 mL of 0.5 M sulfuric acid was added to the conical flask. The conical flask was heated with a small fire until no more CO₂ was emitted and the residue was free of black particles (this process took about 5 minutes). The resulting solution was diluted to 30 mL and heated to 75–85 ° C, and then the remaining sodium oxalate solution was titrated with a 0.02 M KMnO₄ solution immediately. The endpoint criterion was that the solution became pink and did not disappear in 30s. For another, the content of manganese in the sample needs to be determined, excessive KMnO₄ needs to be removed by means of adding a small amount of Na₂C₂O₄, After the solution has cooled down, transfer it to a 100mL volumetric flask, dilute with ultrapure water to volume, and mix. Subsequently, pipetted 20-ml solution into a 150 ml conical flask from the volumetric flask, dilute with ultrapure water to 50 ml, and then add 0.1 g of hydroxylamine hydrochloride, 2 mL of triethanolamine, 10 mL of buffer solution with the pH = 10, and use chrome black T as an indicator. EDTA was dropped until the solution became pure blue as the end point.

The calculated equations are shown as following:

$$w\left(\text{M}\text{n}\text{O}2\right)=\frac{\left(a-b\times 5/2\right)\times M\left(MnO2\right)}{\text{W}}\times 100\text{%}$$

$$w\left(Mn\right)=\frac{\left(\text{c}\times 5-b\right)\times M\left(Mn\right)}{\text{W}}\times 100\text{%}$$

$$x=\frac{\left(a-b\times 5/2\right)+\left(5c-b\right)}{5\text{c}-\text{b}}=1+\frac{a-5b∕2}{5c-b}$$

where w (MnO₂) and w (Mn) are the manganese dioxide content and the manganese content in the samples (%), respectively, M (MnO₂) and M (Mn) are the molar mass (g · mol^− 1) of MnO₂ and the molar mass (g · mol^− 1) of Mn, respectively. In this equation, a is the amount of substance (mol) of Na₂C₂O₄, b is the amount of KMnO₄ that is consumed when titrating the remaining Na₂C₂O₄ (mol), c is the amount of EDTA (mol), and w is the weight of the samples (g).

3.1 Influence factors of the gel precursor

3.1.1 The effects of initial concentration of reactant

The citric acid and manganese acetate were reacted at the same concentration, and the initial concentrations of the reactants were 0.1, 0.3, 0.5, 0.7 and 1.0 M, respectively, the other conditions were the same as the orthogonal experiments. The experimental results presented that a uniform and transparent xerogel could be obtained when the initial concentration of the solution was 0.1 M. The precipitation was not generated during the process of changing from sol to wet gel at the initial concentration was 0.3 M, but a few of crystals were precipitated during the process of changing from wet gel to dry gel. Moreover, when the initial concentration was 0.5 M, snowflake-like crystals were precipitated during the process from sol to wet gel. While the concentration was 0.7 M and 1.0 M, more crystals appeared in less time.

These results suggested that the lower the concentration, the better the dispersibility of the colloidal particles, the smaller the chance of collision between particles. The particles were difficult to agglomerate into large particles and precipitate, so it was easy to obtain a colloidal sol, which was conducive to the formation of uniform and fine particles during the roasting process, thereby obtaining a material with a large specific surface area. With the increase of concentration, the collision probability of colloidal particles increases, and the particles were easy to agglomerate into large particles and settle, led to crystal precipitation. In summary, the content of MnO₂ decreased with the increased of initial concentration of solution. As the concentration increased, the sol formed became increasingly unstable, causing the colloidal particles to condense into larger particles and settle, and further impacted the full sintering of the gel. Simultaneously, the product particles obtained by heat treatment are larger, which was not conducive to subsequent acidification, and eventually results in less manganese oxide formation. The content of MnO₂ obtained was the highest, when the solution concentration was 0.1 M, and the spatial network structure formed by the complexation of Mn²⁺ and citrate was stable, so that a uniform porous gel precursor could be obtained, and thus increased the manganese oxide content after roasting and acidification. However, the efficiency of production would decrease accordingly if the concentration continued to decrease. Thus, 0.1M was chosen as the initial concentration of reactant in this experiment.

3.1.2 The effects of the ratio of reagent solution

The citric acid and manganese acetate were mixed at a ratio of 0.2:1, 0.3:1, 0.4:1, 0.5:1 and 0.6:1 (molar ratio), respectively, and the other conditions were the same as the orthogonal experiments. In the experimental process, completely transparent sol could be formed when citric acid and manganese acetate were mixed with the molar ratio of 0.4:1 and 0.5:1, respectively. In particular, the product obtained by mixing with mole ratio of 0.5:1 had a large degree of porosity. While the molar ratio of 0.2:1 and 0.3:1, just a few crystals could be separated out during the formation of the gel. Meanwhile, precipitation occurred during the formation of sol when citric acid and manganese acetate were mixed at a molar ratio of 0.6:1. These results indicated that the content of MnO₂ did not increase with the amount of manganese acetate. Thus, an optimal molar ratio of citric acid and manganese acetate was 0.5:1.

3.1.3 The effects of the temperature of water bath

The temperature of water bath was 50, 60, 70 and 80℃ respectively, the other conditions were the same as the orthogonal experiments. The reaction solution was evaporated and dehydrated at the above four water bath temperatures to obtain a light brown sol. In detail, at 50, 60, 70 and 80℃, the conversion time of the solution to light brown sol was 24, 14, 10 and 6h, respectively. Then, the sol obtained at the four water bath temperatures were further dehydrated. Under 50 and 60℃ water bath conditions, uniform and transparent wet-gel were obtained. However, in the water bath at 70 and 80℃, pale pink crystals were precipitated at the bottom of the beaker, especially more crystals were precipitated in the water bath at 80℃. Compared with the other temperature of water bath, the wet gel was obtained in the water bath at 50 and 60℃ were more uniform and transparent. It would be concluded that the higher temperature of water bath, the faster rate of evaporation of water in the system, the faster growth rate of gum nuclei. The colloid gradually became imbalanced after reaching a supersaturated state in the system. In addition, the formation of the colloidal particles promoted as the temperature increased, thereby increasing the probability of collision between particles. The colloidal particles would agglomerate to form large particles and settle after collided, causing crystals to precipitate in the system. The temperature of the water bath was determined to be 60℃, taking into account the stability of the system and the efficiency of the process.

3.1.4 The effects of the pH of the reaction solution

The pH of reaction solution was set to 3.0, 4.0, 5.0, 6.0, 7.0, and 8.0, respectively, the other conditions were the same as the orthogonal experiments. It could be found that with increasing the pH, the content of manganese dioxide increases first and then decreases by means of chemical analysis. The content of MnO₂ in the product was the highest when the pH of the solution was about 6.0. The experimental results indicated that the solution was difficult to form a transparent sol when the pH was low, and crystals were precipitated in the solution, thus reducing the content of MnO₂ in the product. Due to the fact that the hydrolysis of manganese acetate was incomplete when the pH was low, manganese acetate crystallized out during the evaporation of the solvent. Larger particles were observed in the gel, which caused the sample was difficult to sinter sufficiently during the roasting process, and the particles of the roasted product were larger. In contrast, appropriate ammonia could promote the hydrolysis reaction of manganese salts, which was beneficial to the formation of citrate and Mn²⁺ complexes. During the process of adding ammonia to adjust the pH, a white precipitate appeared in the solution. However, if excessive ammonia was added, the ammonia and Mn²⁺ formed the Mn (OH)₂ precipitate, led to decrease the content of manganese dioxide in the product.

On the basis of the above analysis of the reaction mixture ratio, solution pH, concentration of solution, reaction time and temperature experiments, the optimal experiment conditions of sol-gel method were: n (citric acid): n (manganese acetate) = 0.5:1, C₀ = 0.1M, pH ≈ 6.0, and the reaction temperature of water bath was 60℃. Moreover, the gel precursor was calcined in a muffle furnace at 280℃ for 10 h, and high temperature acidification for 3h in a 2M sulfuric acid solution.

3.2 Structure and characterizations of the MnO₂ catalyst

The XRD patterns of MnO₂ were presented in Fig. 1, where α-MnO₂ was represented by the number 1, and γ-MnO₂ was represented by the number 2. To confirm the structure of MnO₂, the obtained XRD patterns were compared with α-MnO₂ (JCPDS44-041) and γ-MnO₂ (JCPDS14-0644) standard cards, and diffraction peaks of MnO₂ at crystal diffraction angles of 12.400, 17.700, 28.400, 37.200, 49.800, 59.800, and 69.00, suggesting that the α- MnO₂ was existing in the samples [43]. Simultaneously, diffraction peaks appeared at 41.800, 56.000, 65.100, indicating that the γ-MnO₂ was existing in the samples. In summary, the MnO₂ sample prepared by sol-gel method was considered as mixed crystal of α-MnO₂ and γ-MnO₂.

Figure 1 The XRD patterns of manganese dioxide by sol-gel method

In order to determine the structure and the electrochemical activity of MnO₂ samples, the electrodes prepared by mixing MnO₂ and carbon powder in different proportions were subjected to cyclic voltammetry in a three-electrode system. Figure 2 presented the CV curves of the electrodes with 20%, 40% and 60% MnO₂ mass fraction.

It could be observed that the peak potentials of the three samples were basically the same, and the three peaks were also similar in the shape. At about 0.2V and − 0.68V, two reduction peaks were observed during the first reduction process of MnO₂. In addition, the reaction peak was observed at -0.68V more or less, which indicated that the Mn²⁺ as well as Mn₃O₄ were generated in this potential region. The chemical reactions mechanism of γ-MnO₂ were shown as following:

γ-MnO₂ + H₂O + e=MnOOH + OH^- (8)

MnOOH + e = HMnO₂ (9)

MnOOH + HMnO₂ = Mn₃O₄ + H₂O + OH^- (10)

In these reactions, the reaction (8) corresponded to the reduction peak at 0.2V, the generated peak at -0.68V corresponded to the reduction product of Mn₃O₄ obtained according to reaction (9) and (10). After that, the peak shape of cyclic voltammetry did not change significantly, just the peak position shifted.

Meanwhile, during the retrace process, two oxidation peaks appeared at approximately − 0.12V and 0.43V, respectively. In detail, the corresponding oxidation peaks were not obvious at 0.43V when the mass fraction of MnO₂ was 40% and 60%, and the peak was almost invisible when the mass fraction of MnO₂ was 20%. The reason for this situation is that oxygen evolution was relatively serious during the experiment. Compared with situation at about 0.43V, an evident hydrogen evolution phenomenon was shown at about − 1.25V, bubbles were also observed correspondingly during the experimental process.

When analyzing the microscopic mechanism of MnO₂ electrode, it is generally believed that the γ-MnO₂ on the electrode will be reduced to α-MnOOH with the same crystalline form. The crystal structure of γ-MnO₂ only expands but is not destroyed, so the reduction reaction is a reversible homogeneous reaction process. The first oxidation peak that appeared at about − 0.12V, corresponded to the situation where Mn (OH)₂ was disproportionated to generate γ-Mn₂O₃. The second oxidation peak corresponded to a disproportionation reaction of Mn (OH)₂ to generate a mixture of γ-MnOOH and β-MnOOH, and the generated γ-MnOOH would be further oxidized to δ-MnO₂.

In addition, the CV curves presented that the peak width decreased as the mass fraction of MnO₂ increased. Because with the increased of the content of carbon powder in the electrode, led to the conductivity of the electrode material was enhanced and the peak of MnO₂ gradually became non-obvious. Moreover, the binder was added during the process of making the C / MnO₂ electrodes, resulting in deviations in electrode potential and the current. Furthermore, During the preparation of MnO₂ and electrodes, other interference factors would cause impurities in the MnO₂ samples, and thus impacting the catalytic performance of the MnO₂ electrode.

3.3 Effects of the concentration of H₂O₂ on the performances of the electrodes

In the metal semi-fuel cell, hydrogen peroxide is often used as an oxidant. The following mechanism describes the reaction of H₂O₂ on the electrode surface [44]:

(1) In alkaline media, H₂O₂ is reduced to OH⁻:

H₂O₂ + 2e-→2OH⁻ (E₀ = 0.87V vs SHE) (3.4)

(2) in an acidic media, H₂O₂ is reduced to water:

H₂O₂ + 2e-+2H+→2H₂O (E₀ = 1.77V vs SHE) (3.5)

3.3.1 MnO₂-free electrodes

Due to the fact that MnO₂ was mixed with carbon powder to prepare the electrodes, the blank contrast experiment was performed to detect the catalytic activity of carbon powder to H₂O₂. Electrodes prepared of carbon powder were used to replace C/MnO₂ electrode as the working electrode. CV performance tests were performed in 0.0, 0.1, 0.2, 0.3 and 0.4M H₂O₂ solutions, respectively. The CV curves were displayed in Fig. 3.

As shown in Figure. 3, H₂O₂ presented a reduction trend from about − 0.35V. It can be observed that the current gradually increased as the voltage moved negatively. Moreover, with the increase of the concentration of H₂O₂, the trend of increasing current became more obvious. In detail, the current variation was the largest, from − 5 mA to -25 mA when the concentration of H₂O₂ was 0.4M, and the overpotential was also changing. These results suggested that carbon powder had electrocatalytic activity for the reduction of hydrogen peroxide. However, due to the small current variation range, we did not take out of account the effect of carbon powder on the reduction of H₂O₂ in the subsequent analysis.

3.3.2 Catalytic performances of MnO₂-containing

Figure 4a, b, and c illustrated the CV curves of the electrodes with 20%, 40%, and 60% MnO₂ mass fractions in different concentrations of H₂O₂ solution, respectively. In this study, the concentrations of H₂O₂ solution were set to 0.0, 0.1, 0.2, 0.3, 0.4 and 0.5M, respectively.

As shown in the Fig. 4, when the potential was below − 0.15V, the tendency of H₂O₂ reduction began to become obvious, while the current fell down, and the change of current gradually increased with the increasing concentration of H₂O₂. It is because of the following reasons: When the concentration of H₂O₂ was small, the amount of H₂O₂ in the electrode and its diffusion layer participating in the catalytic reduction of MnO₂ cathode was small. Furthermore, the amount of manganese dioxide cathode reduction gradually increased with the increasing concentration of H₂O₂, so the current increased, resulting in a decrease in polarizability. Figure 4a, b and c presented when the concentrations of H₂O₂ were 0.0M, 0.1M, 0.2M, respectively, the polarizabilities were greater than 0.3M, and the polarizabilities of H₂O₂ at concentrations of 0.4 M and 0.5 M were also greater than that of 0.3 M, suggesting that compared with the current, the polarizability did not always decrease as the concentration of H₂O₂ increased. This is because that the higher the concentration of H₂O₂, the more severe the self-decomposition reaction. Therefore, the partial self-decomposition of H₂O₂ around the electrode (can be seen in the experiment to generated air bubbles) may cause the actual active electrochemical area of the MnO₂ electrode contacting with H₂O₂ to decrease, the electrochemical amount of MnO₂ becomes less, which leads to an increase in polarizability. Under the circumstances of the same discharge current, the smaller the polarization rate, the higher the battery voltage when the battery is operated, and the more it will meet with the requirements of the battery. Thus, 0.3M was termed as the optimal concentration of H₂O₂ in this study.

H₂O₂ with a concentration of 0.3 M was selected to measure the current and calculate the current density. The area of electrode was 1 × 1cm² during the calculation, and the measured current density was shown in Table 2.

Table 2

The current density corresponding to the mass fractions of MnO₂
The mass fractions of MnO₂	20%	40%	60%
The current density of H₂O₂ (mA·cm^− 2)	57.8	67.8	66.7

3.4. Effects of the content of MnO₂

Figure. 5a presented the CV curves obtained in a 0.3 M H₂O₂ solution. When the mass fraction of MnO₂ in the electrode was 40%, the polarizability of CV curve was the smallest. The smaller the polarization of the curve, the better the performance of the electrode. Therefore, in a 0.3 M H₂O₂ electrolyte solution, the electrode with a MnO₂ mass fraction of 40% corresponded to the most excellent electroactivity. In H₂O₂ solution with a concentration of 0.4M (Fig. 5b), it was clear to similarly calculate the polarizability of the electrode was the smallest when the mass fraction of MnO₂ was 40%. This result was the same as shown in Figure. 5a. Finally, it could be concluded that MnO₂ with mass fraction of 40% has the best electrocatalytic activity under the same concentration of H₂O₂ solution.

In this paper, the MnO₂ sample was prepared by sol-gel method and its electrochemical activity for H₂O₂ electroreduction was investigated. Appropriate reaction condition can directly affect the gel precursor generation, which was the key for the preparation of MnO₂.The optimal preparation conditions for the gel precursor were: n (citric acid): n (manganese acetate) = 0.5: 1, initial concentration of reactant C₀ = 0.1M, pH ≈ 6, temperature of reaction was about 60 ℃. Meanwhile, MnO₂ was successfully introduced to C/Ni foam cathode for decreasing the polarizability, and thus led to enhance the catalytic activity of the electrode. In addition, as the increase of H₂O₂ concentration, the amount of H₂O₂ in the electrode and its diffusion layer participates in the cathode catalytic reduction of MnO₂ will increase, so that the polarizability will be reduced. However, excessive concentrations of H₂O₂ would lead to serious self-decomposition reaction, and thus weaken the catalytic activity of the electrode. Consequently, under the condition that the mass fraction of MnO₂ in the electrode material was 40% and the concentration of H₂O₂ was 0.3M, the catalytic activity of MnO₂ to H₂O₂ is maximum. All the results reported here provided potential design and operation strategies for MnO₂ cathode catalyst.

Ethics approval

Ethical approval does not apply to this article.

Competing interests

The authors declare no competing interests.

Author contribution

A (Shuncheng Yang and Zhaoyang Cui) wrote the main manuscript text. B (Xuegang Cai) provided technical guidances to author. C(Yanzhuo Lv) and D (Yan Xu) provided authors with thesis advices and guidances.

Funding

This work was financially supported by the students innovation and entrepreneurship training program project of Harbin Engineering University in 2023.

Availability of data and materials

The data that support the findings of this study are available from the corresponding author upon reasonable request.

Li Y, Lu J. Metal–air batteries: will they be the future electrochemical energy storage device of choice?[J]. ACS Energy Letters, 2017, 2(6): 1370–1377.
Lei T, Tian Y M, Wang G L, et al. An Alkaline Al–H₂O₂ Semi-Fuel Cell Based on a Nickel Foam Supported Co3O4 Nanowire Arrays Cathode[J]. Fuel Cells, 2011, 11(3): 431–435.
Yang F, Cheng K, Mo Y, et al. Direct peroxide–peroxide fuel cell – Part 1: The anode and cathode catalyst of carbon fiber cloth supported dendritic Pd[J]. Journal of Power Sources, 2012, 217(none):562–568.
Pournaghi-Azar M H, Ahour F. Electrochemical reduction and kinetics of hydrogen peroxide on the rotating disk palladium-plated aluminum electrode modified by Prussian blue film as an improved electrocatalyst[J]. Journal of Solid State Electrochemistry, 2010, 14(5):823–828.
Cao D, Sun L, Wang G, et al. Kinetics of hydrogen peroxide electroreduction on Pd nanoparticles in acidic medium[J]. Journal of Electroanalytical Chemistry, 2008, 621(1):31–37.
Tian Y, Huang J, Gao Y, et al. Preparation and electrocatalytic performance of Fe–N–C for electroreduction of H2O2[J]. Journal of Solid State Electrochemistry, 2012, 16(5):1901–1906.
Jing X, Cao D, Liu Y, et al. The open circuit potential of hydrogen peroxide at noble and glassy carbon electrodes in acidic and basic electrolytes[J]. Journal of Electroanalytical Chemistry, 2011, 658(1–2):46–51.
Wang X, Ye K, Sun C, et al. Simple fabrication of pineapple root-like palladium-gold catalysts as the high-efficiency cathode in direct peroxide-peroxide fuel cells[J]. Journal of Colloid and Interface Science, 2017, 498:239–247.
Cardenas-Valencia A M, Short R T, Adornato L, et al. Semi-fuel cell studies for powering underwater devices: integrated design for maximized net power output[C]// Unattended Ground, Sea, and Air Sensor Technologies and Applications XII. International Society for Optics and Photonics, 2010.
An L, Zhao T S, Xu J B. A bi-functional cathode structure for alkaline-acid direct ethanol fuel cells[J]. International Journal of Hydrogen Energy, 2011, 36(20):13089–13095.
Wang Q, Zheng W, Chen H, et al. Plasmonic-induced inhibition and enhancement of the electrocatalytic activity of Pd-Au hetero-nanoraspberries for ethanol oxidation[J]. Journal of Power Sources, 2016, 316:29–36.
Yi L, Wei W, Zhao C, et al. Electrochemical oxidation of sodium borohydride on carbon supported Pt-Zn nanoparticle bimetallic catalyst and its implications to direct borohydride-hydrogen peroxide fuel cell[J]. Electrochimica Acta, 2015, 158(Complete):209–218.
Liu J, Yi L, Wang X, et al. Investigation of nanoporous carbon supported palladium–zinc nanocomposites as anode catalysts for direct borohydride–hydrogen peroxide fuel cell[J]. International Journal of Hydrogen Energy, 2015, 40(23):7301–7307.
Jing L, Zhao Q, Chen S, et al. Nanoporous carbon supported platinum-copper nanocomposites as anode catalysts for direct borohydride-hydrogen peroxide fuel cell[J]. Electrochimica Acta, 2015, 171: 96–104.
Li Y, Cao D, Liu Y, et al. CuO nanosheets grown on cupper foil as the catalyst for H₂O₂ electroreduction in alkaline medium[J]. International Journal of Hydrogen Energy, 2012, 37(18):13611–13615.
Gao Y Y, Cao D X, Wang G L, et al. Catalytic Behavior of NiCo₂O₄ for H₂O₂ Electroreduction in Alkaline Medium[J]. ACTA PHYSICO-CHIMICA SINICA, 2010, 26(1):29–33.
Sanli A E, Ayta A. Response to Disselkamp: Direct peroxide/peroxide fuel cell as a novel type fuel cell[J]. International Journal of Hydrogen Energy, 2011, 36(1):869–875.
Zhang Y, Zang J, Huang J, et al. Microwave synthesis and properties of MnO₂/CNTs non-precious metal catalyst for oxygen reduction reaction in alkaline solution[J]. Journal of Applied Electrochemistry, 2018, 48(2):157–164.
Yu Q, Xu J, Wu C, et al. MnO₂ Nanofilms on Nitrogen-Doped Hollow Graphene Spheres as a High Performance Electrocatalyst for Oxygen Reduction Reaction[J]. ACS Applied Materials & Interfaces, 2016, 8(51):35264–35269.
Fu M, Zhu Z, Zhang Z, et al. Microwave assisted growth of MnO₂ on biomass carbon for advanced supercapacitor electrode materials[J]. Journal of Materials Science, 2021:1–10.
Sun Y, Xing Y, Ma N, et al. Manganese dioxide nanosheet assemblies as electrode materials for electrocapacitive storage of magnesium ions[J]. Electrochimica Acta, 2019, 308:150–157.
Kailin, Li, et al. Tuning MnO₂ to FeOOH replicas with bio-template 3D morphology as electrodes for high performance asymmetric supercapacitors[J]. Chemical Engineering Journal, 2019,370:136–147.
Yan W, Jin G, Tingfeng W, et al. Mesoporous Transition Metal Oxides for Supercapacitors[J]. Nanomaterials, 2015, 5(4):1667–1689.
Wei W, Cui X, Chen W, et al. Manganese oxide-based materials as electrochemical supercapacitor electrodes[J]. CHEMICAL SOCIETY REVIEWS, 2011, 40(3):1697–1721.
Devaraj S, Munichandraiah N. Effect of Crystallographic Structure of MnO₂ on Its Electrochemical Capacitance Properties[J]. The Journal of Physical Chemistry C, 2008, 112(11):4406–4417.
Xu M, Kong L, Zhou W, et al. Hydrothermal Synthesis and Pseudocapacitance Properties of α-MnO₂ Hollow Spheres and Hollow Urchins[J]. Journal of Physical Chemistry C, 2007, 111(51):19141–19147.
Liu G, Kang C, Fang J, et al. MnO₂ nanosheet-coated Co₃O₄ complex for 1.4 V extra-high voltage supercapacitors electrode material[J]. Journal of Power Sources, 2019, 431(AUG.15):48–54.
Osgood H, Devaguptapu S V, Xu H, et al. Transition metal (Fe, Co, Ni, and Mn) oxides for oxygen reduction and evolution bifunctional catalysts in alkaline media[J]. Nano Today, 2016,11(5):601–625.
Roche I, Eric Chaînet, Chatenet M, et al. Carbon-Supported Manganese Oxide Nanoparticles as Electrocatalysts for the Oxygen Reduction Reaction (ORR) in Alkaline Medium: Physical Characterizations and ORR Mechanism[J]. The Journal of Physical Chemistry C, 2006, 111(3):1434–1443.
Feng X, Zhang Y, Song J, et al. MnO₂/Graphene Nanocomposites for Nonenzymatic Electrochemical Detection of Hydrogen Peroxide[J]. Electroanalysis, 2014, 27(2):353–359.
Elayakumar K, Manikandan A, Dinesh A, et al. Enhanced magnetic property and antibacterial biomedical activity of Ce³⁺ doped CuFe₂O₄ spinel nanoparticles synthesized by sol-gel method[J]. Journal of Magnetism and Magnetic Materials, 2019, 478: 140–147.
Pietrzyk B, Miszczak S, Kaczmarek U, et al. Low friction nanocomposite aluminum oxide/MoS₂ coatings prepared by sol-gel method[J]. Ceramics International, 2018:8534–8539.
Ahn M S, Ahmad R, Yoo J Y, et al. Synthesis of manganese oxide nanorods and its application for potassium ion sensing in water[J]. Journal of Colloid & Interface Science, 2018, 516:364–370.
Wang X, Yuan A, Wang Y. Supercapacitive behaviors and their temperature dependence of sol–gel synthesized nanostructured manganese dioxide in lithium hydroxide electrolyte[J]. Journal of Power Sources, 2007, 172(2):1007–1011.
Miao L, Wang J, Zhang P. Review on manganese dioxide for catalytic oxidation of airborne formaldehyde[J]. Applied Surface Science, 2019, 466: 441–453.
Zhu S, Wang J, Nie L. Progress of Catalytic Oxidation of Formaldehyde over Manganese Oxides[J]. ChemistrySelect, 2019, 4(41): 12085–12098.
Dolhun J J. Observations on manganese dioxide as a catalyst in the decomposition of hydrogen peroxide: a safer demonstration[J]. Journal of Chemical Education, 2014, 91(5): 760–762.
Ye D, Li H, Liang G, et al. A three-dimensional hybrid of MnO₂/graphene/carbon nanotubes based sensor for determination of hydrogen-peroxide in milk[J]. Electrochimica Acta, 2013, 109: 195–200.
Li X, Huang Y, Zeng J, et al. Mobility Improvement of Sol–Gel Method Processed Transparent SnSx Thin Films by Na Doping[J]. Journal of Nanoscience and Nanotechnology, 2020, 20(8): 5102–5106.
Purcar V, Rădiţoiu V, Dumitru A, et al. Antireflective coating based on TiO₂ nanoparticles modified with coupling agents via acid-catalyzed sol-gel method[J]. Applied Surface Science, 2019, 487: 819–824.
Ribeiro, Miranda, Marcus, et al. The Scherrer equation and the dynamical theory of X-ray diffraction[J]. Acta crystallographica. Section A. Foundations of crystallography, 2016,72(3)385–390.
Vygodina T V, Kaminskaya O P, Konstantinov A A, et al. Effect of Ca²⁺ on the redox potential of heme a in cytochrome c oxidase[J]. Biochimie, 2018, 71–78.
Miao L, Wang J, Zhang P. Review on manganese dioxide for catalytic oxidation of airborne formaldehyde[J]. Applied Surface Science, 2019,466:441–453.
Dou J, Zhu G, Hu B, et al. Wall thickness-tunable AgNPs-NCNTs for hydrogen peroxide sensing and oxygen reduction reaction[J]. Electrochimica Acta, 2019, 306:466–476.

No competing interests reported.

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Cathodic Performances of MnO2 Induced C/Ni Foam Electrode for H2O2

Status:

Version 1

Abstract

Figures

Introduction

Materials and methods

2.1 Chemicals

2.2 Preparation and characterization of MnO₂

2.3 Electrode preparation and electrochemical measurement

2.4 Analytical methods and data analysis

Results and discussion

3.1 Influence factors of the gel precursor

3.1.1 The effects of initial concentration of reactant

3.1.2 The effects of the ratio of reagent solution

3.1.3 The effects of the temperature of water bath

3.1.4 The effects of the pH of the reaction solution

3.2 Structure and characterizations of the MnO₂ catalyst

3.3 Effects of the concentration of H₂O₂ on the performances of the electrodes

3.3.1 MnO₂-free electrodes

3.3.2 Catalytic performances of MnO₂-containing

3.4. Effects of the content of MnO₂

Conclusion

Declarations

Ethics approval

Competing interests

Author contribution

Funding

Availability of data and materials

References

Additional Declarations

Status:

Version 1

Cathodic Performances of MnO2 Induced C/Ni Foam Electrode for H2O2

Status:

Version 1

Abstract

Figures

Introduction

Materials and methods

2.1 Chemicals

2.2 Preparation and characterization of MnO2

2.3 Electrode preparation and electrochemical measurement

2.4 Analytical methods and data analysis

Results and discussion

3.1 Influence factors of the gel precursor

3.1.1 The effects of initial concentration of reactant

3.1.2 The effects of the ratio of reagent solution

3.1.3 The effects of the temperature of water bath

3.1.4 The effects of the pH of the reaction solution

3.2 Structure and characterizations of the MnO2 catalyst

3.3 Effects of the concentration of H2O2 on the performances of the electrodes

3.3.1 MnO2-free electrodes

3.3.2 Catalytic performances of MnO2-containing

3.4. Effects of the content of MnO2

Conclusion

Declarations

Ethics approval

Competing interests

Author contribution

Funding

Availability of data and materials

References

Additional Declarations

Status:

Version 1

2.2 Preparation and characterization of MnO₂

3.2 Structure and characterizations of the MnO₂ catalyst

3.3 Effects of the concentration of H₂O₂ on the performances of the electrodes

3.3.1 MnO₂-free electrodes

3.3.2 Catalytic performances of MnO₂-containing

3.4. Effects of the content of MnO₂