Photocatalytic hydrogen peroxide (H2O2) generation represents a promising approach for artificial photosynthesis. However, the sluggish half-reaction of water oxidation significantly limits the efficiency of H2O2 generation. A substitutional reaction of oxidation with accelerated kinetics to produce value-added chemicals holds promise to tackle this challenge. Here, a benzylamine oxidation with more favorable thermodynamics is employed as the half-reaction to couple with H2O2 generation in water by using defective zirconium trisulfide (ZrS3) nanobelts as photocatalyst. The ZrS3 nanobelts with disulfide (S22-) and sulfide anion (S2-) vacancies exhibit an excellent photocatalytic performance for H2O2 generation and simultaneous oxidation of benzylamine to benzonitrile with a high selectivity of > 99%. The S22- vacancies are revealed to facilitate the separation of photogenerated charge carriers. The S2- vacancies can significantly improve the electron conduction, hole extraction, and kinetics of benzylamine oxidation. As a result, the use of defective ZrS3 nanobelts yields a high production rate of 78 and 32 µmol h-1 for H2O2 and benzonitrile, respectively, under a simulated sunlight irradiation.
Article
Efficient Photocatalytic Hydrogen Peroxide Generation Coupled with Selective Benzylamine Oxidation over Defective ZrS3 Nanobelts
https://doi.org/10.21203/rs.3.rs-73943/v1
This work is licensed under a CC BY 4.0 License
Journal Publication
published 01 Apr, 2021
Version 1
posted
You are reading this latest preprint version
Photocatalytic hydrogen peroxide generation
artificial photosynthesis
selective benzylamine oxidation
defective ZrS3 nanobelts
Artificial photosynthesis, i. e. the conversion of solar energy into chemical energy, is considered as one of the promising approaches to synthesize chemicals with the unlimited energy source and minimized environmental problems.1,2 As a novel liquid solar fuel generated by artificial photosynthesis, hydrogen peroxide (H2O2) has attracted growing attention because of its high commercial value and low transportation cost.3 Substantial efforts have been devoted to the development of effective photocatalysts for the H2O2 generation from water and O2.4 In this photocatalytic process, the sluggish oxidation of water induced by the photogenerated valence holes is a limiting factor for the production of H2O2.5-9 Most previous reports focused on improving the half-reaction of O2 reduction, e. g. by consuming holes with sacrificial agents, such as isopropyl alcohol, benzyl alcohol, and 2-PrOH.3,10,11 However, the development of an alternative oxidation reaction with accelerated kinetics to produce value-added chemicals was rarely reported. On the other hand, selective oxidation of amines to nitriles with lower oxidation potential than water plays an vital role in both laboratorial and industrial synthetic process since nitriles are the important intermediates during the synthesis of fine chemicals, pharmaceuticals, and agrochemicals.12-19 Intensive research has been carried out to synthesize nitriles from primary nitriles through dehydrogenation.20-25 However, most of the reactions are conducted in organic solvents under harsh conditions, such as high-temperature, exposure to high-pressure oxygen or air, and presence of oxidants. Thus, the development of artificial photosynthesis with appropriate photocatalysts for such reactions is highly desirable for the production of nitriles in an economically-viable and environment-friendly way.
Monoclinic zirconium trisulfide (ZrS3) (ICCD PDF no. 30-1498), a layered n-type transition metal trichalcogenide (TMT), has recently drawn great research interest due to the extraordinary properties arising from its unique disulfide anions (S22-).26 ZrS3 has shown a good optical responsivity of 290 mA W−1 with an in-plane hole and electron mobility at a magnitude of 102 and 103 cm2 V−1 s−1, respectively.27-30 In particular, ZrS3 possesses a bandgap of ~2 eV with a more negative conduction band minimum (CBM) than the H2 evolution potential,31 making ZrS3 a promising semiconductor for photocatalytic and photoelectrochemical applications. The previous studies on zirconium nitride have demonstrated that its superior performance for O2 reduction stems from the interaction between Zr sites and oxide species, where the Zr d-orbitals make a strong contribution.32 Intriguingly, the conduction band of ZrS3 is mainly composed of Zr d-orbitals,27,29 which has a much more negative potential than the reducing potential of O2 to H2O2. Therefore, ZrS3 shows great potential for the photocatalytic H2O2 generation.
There are three categories of S (S1, S2, and S3) environments in monoclinic ZrS3 lattice, where S1 denotes the sulfide ion (S2-) and S2, S3 are interpreted as the S22- (Schematic 1a and b).33 Recently, both theoretical calculations and experimental investigations have demonstrated that moderate S22- vacancies can greatly promote the separation of photogenerated charge carriers in TMTs (Schematic S1a and b).34,35 In addition, the anion vacancies existing on the surface of n-type semiconductors can further improve its photocatalytic and photoelectrochemical performance by accelerating the kinetics of hole transfer on the surface.36-39 The crystal structure analysis of ZrS3 inspires us that the S22- and S2- vacancies can be separately introduced into ZrS3 by different methods (Schematic 1 and S1). Experimentally, hexagonal ZrS2 (ICCD PDF no. 11-0679) is usually obtained by vacuum annealing of monoclinic ZrS3 at elevated temperatures.40 Only one type of Zr (Zr1) and S (S1) environment exists in ZrS2, where the Zr1-S1 bond length is similar to that in ZrS3 (Schematic 1a-c). Besides, ZrS2 shows a similar layered structure to ZrS3, and atomic layers in both materials are parallel to the (001) plane (Schematic S1c-f). When ZrS3 transforms into ZrS2, it does not need much tweaking of the framework along both [010] and [001] directions (Schematic S1c and e), but it is required to adjust the framework along the [100] direction (Schematic 1d and f). Schematic 1 clearly suggests that the ZrS3 can transform into ZrS2 by two steps: the first step can be the desulfurization of ZrS3 to release S2 or S3 ions to form a distorted crystal structure of ZrS2 (Schematic 1a, b, d and e), and then the distorted crystal structure undergoes structural relaxation by tuning the length and angle of Zr-S bonds to form ZrS2 without breaking or regrouping the bonds (Schematic 1b, c, e and f). Thus, the high-temperature vacuum annealing is expected to be an effective scheme to produce S22- vacancies in ZrS3. On the other hand, S2- ions have the high adaptability when coordinated with metal ions, which can serve as either terminal or bridge ions to interact with metals (especially for alkali metals). This different with the Sx2- (x≥2) ions that are difficult to bond with metals (Schematic S1g).41 Moreover, ZrS3 is easily formed as nanobelts (NBs) with rich S2- ions exposed at the edges (Schematic 1h and i). As a typical alkali metal with high reducibility, Li has been widely utilized to prepare superconducting materials and induce vacancies.42-45 Therefore, such Li-based treatment could be an effective approach to induce S2- vacancies on ZrS3.
Here, ZrS3 NBs with both S22- and S2- vacancies are employed to enhance the photocatalytic production of H2O2 coupled with the selective oxidation of benzylamine to benzonitrile (BN) in water. The impacts of S22- and S2- vacancies on modulating the charge carrier dynamics and photocatalytic performance are systematically investigated. The S22- vacancies can significantly facilitate the separation of photogenerated charge carriers; while the S2- vacancies are demonstrated to not only promote the electron conduction and hole extraction in photocatalytic process but also improve the kinetics of benzylamine oxidation. As a result, the use of defective ZrS3 NBs as photocatalyst produces H2O2 and BN at a high rate of 78 and 32 μmol h-1 respectively, under the illumination of a simulated sunlight.
Synthesis and band structures of photocatalysts. ZrS3 NBs were synthesized via a chemical vapor transport of S powder to Zr powder using iodine as a transport agent. ZrS3 with S22- vacancies (ZrSS2-x) was obtained by the re-annealing of the as-grown ZrS3 NBs at 700 ℃ for 15 min under vacuum. ZrSS2-x with S2- vacancies (ZrS1-yS2-x) was prepared through a low-temperature solvothermal treatment by using Li-dissolved ethanediamine. The x-ray diffraction (XRD) pattern indicates the formation of ZrS3 in the monoclinic phase (ICCD PDF no. 30-1498), and the vacuum annealing and further Li treatment did not induce any phase transition in ZrSS2-x and ZrS1-yS2-x NBs (Figure S1). The obtained ZrS3 was formed as NBs with the width ranging from 400 nm to 3 μm and length in tens of micrometers (Figure 1a-c). The individual ZrS3 NB is confirmed as the single crystal along [010] direction by the transmission electron microscopy (TEM) and corresponding selected area electron diffraction (SAED) characterization (Figure 1d). It is demonstrated that the ZrS3 layer is parallel to the axial direction of NB, which is in favor of charge carrier transport.34 As shown in the diffuse reflectance UV–vis spectra (Figure 1e), both ZrS3 and ZrSS2-x NBs absorb light with the wavelength up to ~650 nm, corresponding to a bandgap of 2.02 eV (Figure S2). ZrS1-yS2-x NBs present a slight red-shift of absorption spectrum, revealing a smaller bandgap of 1.98 eV. The Mott−Schottky plots for all three samples exhibit positive slopes, indicating the n-type behavior of ZrS3 (Figure 1f). The flat band potentials (Efb) of ZrS3, ZrSS2-x, and ZrS1-yS2-x are estimated to be -0.10, -0.11, and -0.18 V versus reversible hydrogen electrode (VRHE), respectively (Figure 1g and S3). Efb is commonly used to estimate the CBM for a series of n-type semiconductors at the surface in an aqueous environment, which agreed with their theoretically determined values.1,38,46-48 Previsous stduies on the energy positions of semicondutors have shown that the CBM of zirconium-based sulfides is very close to their Efb,31,47 and therefore the CBM of ZrS3, ZrSS2-x, and ZrS1-yS2-x can be directly determined by their Efb. Based on the Mott−Schottky (Figure 1f, g and S3) and UV–vis spectra results, the CBM and valance band maximum (VBM) for ZrS3, ZrSS2-x, and ZrS1-yS2-x were revealed to be -0.10, -0.11, -0.18 VRHE (CBM) and 1.92, 1.91, and 1.80 VRHE (VBM), respectively (Figure 1h and S4). The CBMs of ZrS3, ZrSS2-x, and ZrS1-yS2-x are higher than the potential for two-electron reduction of O2, and their VBMs lie far below the oxidation potential of benzylamine,12,15,48,49 indicating that these photocatalysts are applicable to the photocatalytic O2 reduction and benzylamine oxidation.
Characterizations of vacancy structure. Four characteristic Raman modes of ZrS3 located at ~ 147, 274, 315, and 524 cm-1 were observed in Figure 2a, which are assigned to the rigid chain vibration (I: Agrigid), internal out-of-plane vibrations (II: Aginternal and III: Aginternal), and S–S diatomic motion (IV: Ags–s), respectively.29 The Raman spectra show an obvious red-shift of Ags–s mode by ~5 cm-1 from ZrS3 to ZrSS2-x and ZrS1-yS2-x, originating from the introduction of S22− vacancies.34 We also observed a 3 cm-1 red-shift of Agrigid mode from ZrS3 and ZrSS2-x to ZrS1-yS2-x. Since the Agrigid is correlated to the vibration of quasi-one-dimensional chains in the direction of c axis (Figure S5a), the shift of Agrigid mode in ZrS1-yS2-x results from the introduction of S2− vacancies, which alters the length of Zr–S bonds within each chain. The similar shift of Agrigid mode was also identified from ZrS3 and ZrSS2-x to the only Li-treated ZrS3 (ZrS1-yS) (Figure S5b). The XPS characterization was conducted on these samples to further confirm the vacancy type. After the vacuum annealing, the ZrSS2-x NBs exhibit a slightly higher binding energy of the Zr 3d core level than ZrS3 NBs, consistent with the results from ZrS3 to ZrS2 (Figure S6a).50 Furthermore, ZrSS2-x shows a significant attenuation of S22− 2p peaks with the nearly unchanged S2− 2p peaks compared to ZrS3 (Figure 2b and S6b), indicating the mere increase of S22- vacancies in ZrSS2-x. After further Li treatment, both Zr 3d and S 2p core levels of ZrS1-yS2-x NBs apparently shifted to the higher binding energy by ~0.3 eV with reference to ZrSS2-x (Figure S6a and b) due to the increased electron densities around the Zr sites induced by the S2− vacancies.51 In particular, the intensity of S2− 2p peaks in the ZrS1-yS2-x was clearly lower than that of ZrSS2-x (Figure 2b and S6b), revealing the increase of S2− vacancies. The similar variation of Zr 3d and S 2p spectra observed from ZrS3 to ZrS1-yS further suggest the separate introduction of S2- vacancies by the Li treatment (Figure S6a and b). In addition, the electron paramagnetic resonances (EPR) investigation was also carried out to detect the vacancy structure. Both ZrS1-yS2-x and ZrSS2-x NBs show a similar characteristic peak located at g = 2.004, suggesting the formation of sulfur vacancies.52 The higher signal intensity of ZrS1-yS2-x than that of ZrSS2-x indicates more sulfur vacancies existing in ZrS1-yS2-x NBs. In order to have a direct view of the atomic arrangement for ZrSS2-x and ZrS1-yS2-x NBs, the high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) images were obtained, where the atomic sites can be determined by comparing the HAADF-STEM image with the crystal structure of ZrS3 lattice along the [001] direction (Figure S5c and d). The ZrSS2-x demonstrates the missing atoms only emerging on the S22- sites, as indicated by the red dashed circles in Figure 2d, while the atomic vacancies exist on both S2- (indicated by yellow dashed circles) and S22- sites for ZrS1-yS2-x (Figure 2e).
Photocatalytic performance. The photocatalytic capability of the defective ZrS3 NBs for reducing O2 to create the reactive oxygen species (ROS) was first evaluated by the EPR trapping experiment using 5,5-dimethyl-1-pyrroline N-oxide (DMPO). As illustrated in Figure 3a, four characteristic peaks of DMPO−O2•− were observed for all NBs, confirming the generation of O2•−.52-54 The introduction of S22- vacancies was found to enhance the reduction of O2 to O2•−, and the additional introduction of S2- vacancies led to a further increased photocatalytic activity. Thus, ZrS1-yS2-x NBs possess a high H2O2 evolution rate of 90 μmol h-1 with the presence of benzyl alcohol as the hole scavenger (entry 5 in Table S1), which is higher than most previous reports (Table S2). The wavelength-dependent apparent quantum yield (AQY) for the H2O2 generation on ZrS1-yS2-x agrees well with its absorption spectrum, revealing that the photocatalytic activity originates from the bandgap excitation of ZrS1-yS2-x (Figure 3b). In particular, ZrS1-yS2-x produces an AQY of 11.4 and 10.8 % for the incident light of 400 and 500 nm respectively, and demonstrates a good activity even with the excitation extended to the near-infrared region of ~700 nm. Furthermore, the photocatalyst of ZrS1-yS2-x is able to maintain its activities after being recycled for the same reaction, as presented in Figure 3c. Based on the high activity of ZrS1-yS2-x for H2O2 generation, we further utilized benzylamine to substitute the hole scavenger. The H2O2 evolution rate of ZrS1-yS2-x was decreased to 78 μmol h-1 with the same molar amount of benzylamine as benzyl alcohol, due to the slower oxidation kinetics of benzylamine than that of benzyl alcohol. Simultaneously, the benzylamine was oxidized and converted to BN at a rate of 32 μmol h-1 with a high selectivity of > 99% (entry 2 in Table S1 and Figure 3d). Similar photocatalytic behaviors were also identified on both ZrSS2-x and ZrS3 NBs, which produced the H2O2 at a rate of 58 and 30 μmol h-1 with the hole scavenger (entry 3 and 1 in Table S1), respectively. As a comparison, ZrSS2-x and ZrS3 show a decreased H2O2 evolution rate of 48 and 18 μmol h-1 with the use of benzylamine, and the corresponding BN generation rates are 21 and 7 μmol h-1, respectively (Figure 3d). As a result, the comparison of photocatalytic performance among ZrS1-yS2-x, ZrSS2-x, and ZrS3 reveals the key role of S22- and S2- vacancies on the O2 reduction and benzylamine oxidation.
To provide a deep insight into the effect of defective structures in ZrS3 NBs on its photocatalytic performance, the transient open-circuit potential measurements were performed on ZrS3, ZrSS2-x, and ZrS1-yS2-x NBs to reveal the lifetime of photo-induced charge carriers (Figure S7 and Equation S3). After introducing S22- vacancies, the carrier lifetime of ZrSS2-x was significantly increased to 0.69 s as compared to 0.3 s of ZrS3, while the ZrS1-yS2-x exhibits a further enhanced lifetime of 0.82 s, as shown in Figure 4a. The increased photocurrent for the defective ZrS3 also suggests the role of S22- and S2- vacancies on improving the carrier lifetime and dynamics (Figure S8). In order to explore the underlying mechanism for the lifetime enhancement, the charge carrier dynamics of these samples were extracted through the Mott–Schottky method. According to the Mott–Schottky equation (Equation S1), the electron concentrations of ZrS3, ZrSS2-x, and ZrS1-yS2-x NBs were calculated to be 4.00 × 1018, 5.35 × 1018 and 4.58 × 1019 cm-3, based on the estimated width of the depletion region (wd) under the illumination of 55, 46, and 17 nm, respectively (Equation S2). The similar band bending between ZrS3 and ZrSS2-x suggests that the significantly enhanced carrier lifetime in ZrSS2-x is attributed to the role of S22- vacancies in reducing electron-hole recombination rather than band bending, in agreement with the previous theoretical calculation.35 The significantly reduced wd in ZrS1-yS2-x indicates a large electric field strength on the surface of ZrS1-yS2-x, which can accelerate the extraction of photogenerated holes towards the surface and limit the internal band-to-band recombination. Moreover, the small wd in ZrS1-yS2-x results in a large conduction region for the free electrons compared to ZrS3 and ZrSS2-x, which is beneficial for the electron transport. On the other hand, the reaction kinetics of benzylamine oxidation on the photocatalysts were also investigated by the intensity-modulated photocurrent spectroscopy (IMPS). The typical IMPS plots are shown in Figure S9, and the details for the calculation of rate constant of charge transfer (kt) and surface recombination (krec) are discussed in the supporting information. The higher kt/(kt+ krec) of ZrSS2-x and ZrS1-yS2-x than that of ZrS3 indicates a more efficient benzylamine oxidation for the defective ZrS3 (Figure 4b).37 The ZrSS2-x exhibits a decreased krec compared to ZrS3 (Figure 4c and d), revealing that the more efficient benzylamine oxidation on ZrSS2-x stems from the enhanced carrier lifetime induced by the S22- vacancies. The krec of ZrS1-yS2-x was further decreased due to its efficient hole extraction induced by the large surface band bending. Furthermore, the increase of kt for ZrS1-yS2-x compared to ZrSS2-x suggests that the S2- vacancies can act as an additional photocatalytic layer for the benzylamine oxidation (Figure 4d).
In summary, we have developed an efficient photocatalyst of ZrS1-yS2-x NBs with S22- and S2- vacancies for the integration of photocatalytic H2O2 generation with the selective oxidation of benzylamine to BN in water. The unique S22- vacancies and S2- vacancies in ZrS1-yS2-x are induced separately by the vacuum annealing and Li-treatment, respectively. With the introduction of S22- vacancies, the charge carrier recombination is prominently suppressed, and the surface S2- vacancies are revealed to improve the electron conduction, surface hole extraction, and kinetics of benzylamine oxidation. As a result, the photocatalyst of ZrS1-yS2-x exhibits a high generation rate of 78 and 32 µmol h-1 for H2O2 and BN, respectively. Furthermore, ZrS1-yS2-x NBs possesses a photoexcitation up to ~ 700 nm and delivers a high AQY of 11.4 and 10.8% under the incident light of 400 and 500 nm, respectively. Our results promise a novel strategy for the artificial photosynthesis of liquid solar fuels and other valuable chemicals.
Preparation of ZrS3, ZrSS2-x and ZrS1-yS2-x NBs: The ZrS3 NBs were synthesized through a typical chemical vapor transport process. S (99.5 % purity, Alfa Aesar) and Zr (99.2 % purity, Sigma-Aldrich) powders were mixed according to a molar ratio of 1:3, and 5mg iodine (99.5 % purity, Alfa Aesar) was added as a transport agent. The mixture was sealed in a quartz ampoule (Φ 6 mm × 200 mm) under the vacuum of 10-3 Pa, which was subsequently placed in the centre of a two-zone furnace with a temperature gradient of ca. 15 K/cm from center to edge. The furnace was heated to 650 ℃ and last for 10 h to produce ZrS3 powder. The obtained ZrS3 powder was then dispersed in isopropanol (≥99.5 % purity, Alfa Aesar) at a concentration of 0.5 mg ml-1 followed by the sonication for 15 min.The dispersion was subsequently centrifuged for 10 min at 3000 rpm to remove large aggregates. Finally, the ZrS3 NBs were obtained by the collection from the rest of dispersion.
The ZrSS2-x NBs were prepared using the previously reported vacuum annealing method.34 Specifically, the as-grown ZrS3 NBs were sealed in the quartz ampule again, which was then heated to 700 ℃ and last for 15 mins to fabricate ZrSS2-x NBs. In addition, 0.5 g ZrSS2-x NBs were placed in a 50 mL Teflon-lined autoclave filled with 30 mL ethanediamine (≥98 % purity, Sigma-Aldrich) and 100 mg Li, and the autoclave was subsequently kept in an oven at 120 °C for 24 h. After cooling down to the room temperature, the mixture was first washed in 0.2 M HCl and then rinsed several times in deionized water and ethanol, where the ZrS1-yS2-x NBs was finally obtained.
Characterization of photocatalysts: UV-Vis-NIR spectrometer (Hitachi U4100), field emission SEM (FE-SEM, JEOL JSM6700F), TEM (FEI Titan 80-300, operated at 200 kV), XRD (Bruker D8 Advance), XPS (ESCALAB 250Xi) with Al Ka X-ray as the excitation source, EPR (JEOL FA200) and Raman spectroscopy (Horiba Jobin Yvon Modular Raman Spectrometer) with 514 nm laser excitation were employed to characterize different properties of the defective ZrS3 NBs, e. g. atomic and energy band structure. In particular, the samples for the TEM measurements were suspended in ethanol and supported onto a holey carbon film on a Cu grid.
Coupling photocatalytic H2O2 generation with selective benzylamine oxidation over ZrS3, ZrSS2-x, ZrS1-yS2-x NBs: 50 mg photocatalyst was dispersed in 30 ml H2O with 1 mmol benzylamine. After the sonication for a few seconds, the mixed solution was bubbled by oxygen for 30 s. Subsequently, the solution was sealed and irradiated under an AM 1.5G simulated sunlight of 100 mW cm-2 derived from a 300 W xenon lamp fitted with an AM 1.5 filter. At certain time intervals, the solution was filtrated by a 0.45 μm Millipore filter to remove the photocatalyst. The aqueous and organic phase products were then analyzed by the iodometry and gas chromatograph (GC) measurements, respectively.
The production of H2O2 was analyzed by the iodometry.10 Typically, 50 μL 0.4 M potassium iodide (KI, ≥99 % purity, Sigma-Aldrich) aqueous solution and 50 μL 0.1 M potassium hydrogen phthalate (≥99.5 % purity, Sigma-Aldrich) aqueous solution were added to 2ml obtained aqueous phase product, which was kept for 0.5h. The mixed solution was then detected by UV–vis spectroscopy on the basis of absorbance at 350 nm, from which the quantity of generated H2O2 was estimated. In addition, to analyze organic phase product from the benzylamine oxidation, the organic liquid was first extracted using ethyl acetate (≥99.9 % purity, Sigma-Aldrich) and then detected by the GC characterization.
Photocatalytic H2O2 generation with benzyl alcohol as hole sacrificial reagent: 50 mg catalyst was dispersed in 30 ml H2O containing 1mmol benzyl alcohol. After sonicating for a few seconds, the mixed solution was bubbled by oxygen for 30 s. Subsequently, the solution was sealed and irradiated under an AM 1.5G simulated sunlight of 100 mW cm-2 derived from a 300 W xenon lamp fitted with an AM 1.5 filter. The amount of H2O2 was analyzed by the iodometry. For the action spectrum analysis, the reactions were performed at 298 K under monochromated light irradiation, with the ΦAQY (AQY, apparent quantum yield) determined by the following equation (1):
EPR Trapping Measurements: 4 mg catalyst was suspended in 500 μL CH3OH containing 50 μL DMPO (Sigma-Aldrich for ESR-spectroscopy). After the sonication, the solution was irradiated by a 300 W xenon lamp with a 420 nm filter for 3 min. The resulted solution was subjected to the analysis by using a JEOL (FA200) ESR Spectrometer.
Photoelectrochemical measurement: The photoelectrochemical measurements were performed in a three-electrode system with an electrochemical workstation (Zahner Zennium) under an AM 1.5G simulated sunlight of 100 mW cm-2 (150 W, Newport 94011A LCS-100). Samples on FTO substrates were directly used as the working electrode, with a Pt wire and an Ag/AgCl (KCl saturated) electrode as counter and reference electrodes respectively. All the samples were illuminated through the sample side (front-side illumination). The photoelectrochemical performance was recorded in 0.1 M Na2SO4 electrolyte with 0.1 mM benzylamine. Mott-Schottky plots were derived from impedance-potential tests conducted at a frequency of 1 kHz in dark. IMPS spectra were recorded by the Zahner Zennium C-IMPS system.
Data availability
All data supporting the findings in the article as well as the Supplementary Information files are available from the corresponding authors on reasonable request.
Acknowledgments
The authors acknowledge the financial support from Singapore National Research Foundation under the grant of NRF2017NRF-NSFC001-007, NUS Flagship Green Energy Programme, Fundamental Research Foundation of Shenzhen (No. JCYJ20190808152607389 and No. JCYJ20170817100405375), China Postdoctoral Science Foundation (2020M672794), and Shenzhen Peacock Plan (No. KQTD2016053112042971).
Author contributions
T.Z., H.C., L.H. and C.W. conceived and designed the experiments. T.Z., Z.Y., D.W., L.X., W.Y. and Z.Y. performed the experiments. T.Z., L.X. and H.Z. analyzed the data. T.Z, S.Y., and P.X. wrote the manuscript. All authors discussed the results and commented on the manuscript.
- Shiraishi, Y. et al. Resorcinol–formaldehyde resins as metal-free semiconductor photocatalysts for solar-to-hydrogen peroxide energy conversion. Nat. Mater. 18, 985–993 (2019).
- Chen, S., Takata, T. & Domen, K. Particulate photocatalysts for overall water splitting. Nat. Rev. Mater. 2, 1–17 (2017).
- Kofuji, Y. et al. Hydrogen Peroxide Production on a Carbon Nitride–Boron Nitride-Reduced Graphene Oxide Hybrid Photocatalyst under Visible Light. ChemCatChem 10, 2070–2077 (2018).
- Hou, H., Zeng, X. & Zhang, X. Production of Hydrogen Peroxide by Photocatalytic Processes. Angew. Chem. Int. Ed. 59, 2–23 (2020).
- Teranishi, M., Naya, S.-i. & Tada, H. In situ liquid phase synthesis of hydrogen peroxide from molecular oxygen using gold nanoparticle-loaded titanium (IV) dioxide photocatalyst. J. Am. Chem. Soc. 132, 7850–7851 (2010).
- Kato, S., Jung, J., Suenobu, T. & Fukuzumi, S. Production of hydrogen peroxide as a sustainable solar fuel from water and dioxygen. Energy Environ. Sci. 6, 3756–3764 (2013).
- Moon, G.-h., Kim, W., Bokare, A. D., Sung, N.-e. & Choi, W. Solar production of H2O2 on reduced graphene oxide–TiO2 hybrid photocatalysts consisting of earth-abundant elements only. Energy Environ. Sci. 7, 4023–4028 (2014).
- Isaka, Y., Oyama, K., Yamada, Y., Suenobu, T. & Fukuzumi, S. Photocatalytic production of hydrogen peroxide from water and dioxygen using cyano-bridged polynuclear transition metal complexes as water oxidation catalysts. Catal. Sci. Technol. 6, 681–684 (2016).
- Kim, H.-i., Kwon, O. S., Kim, S., Choi, W. & Kim, J.-H. Harnessing low energy photons (635 nm) for the production of H2O2 using upconversion nanohybrid photocatalysts. Energy Environ. Sci. 9, 1063–1073 (2016).
- Wei, Z. et al. Efficient visible-light-driven selective oxygen reduction to hydrogen peroxide by oxygen-enriched graphitic carbon nitride polymers. Energy Environ. Sci. 11, 2581–2589 (2018).
- Shiraishi, Y. et al. Selective Hydrogen Peroxide Formation by Titanium Dioxide Photocatalysis with Benzylic Alcohols and Molecular Oxygen in Water. ACS Catal. 3, 2222–2227 (2013).
- Huang, Y., Chong, X., Liu, C., Liang, Y. & Zhang, B. Boosting Hydrogen Production by Anodic Oxidation of Primary Amines over a NiSe Nanorod Electrode. Angew. Chem., Int. Ed. 57, 13163–13166 (2018).
- Martin, A. & Kalevaru, V. N. Heterogeneously Catalyzed Ammoxidation: A Valuable Tool for One-Step Synthesis of Nitriles. ChemCatChem 2, 1504–1522 (2010).
- Jagadeesh, R. V., Junge, H. & Beller, M. Green synthesis of nitriles using non-noble metal oxides-based nanocatalysts. Nat. Commun. 5, 1–8 (2014).
- Łuczak, T. Electrochemical behaviour of benzylamine, 2-phenylethylamine and 4-hydroxyphenylethylamine at gold. A comparative study. J. Appl. Electrochem. 38, 43–50 (2007).
- Fleming, F. F., Yao, L., Ravikumar, P., Funk, L. & Shook, B. C. Nitrile-containing pharmaceuticals: efficacious roles of the nitrile pharmacophore. J. Med. Chem. 53, 7902–7917 (2010).
- Wang, T. & Jiao, N. Direct approaches to nitriles via highly efficient nitrogenation strategy through C–H or C–C bond Cleavage. Acc. Chem. Res. 47, 1137–1145 (2014).
- Yan, G., Zhang, Y. & Wang, J. Recent advances in the synthesis of aryl nitrile compounds. Adv. Synth. Catal. 359, 4068–4105 (2017).
- Liu, R. Y., Bae, M. & Buchwald, S. L. Mechanistic insight facilitates discovery of a mild and efficient copper-catalyzed dehydration of primary amides to nitriles using hydrosilanes. J. Am. Chem. Soc. 140, 1627–1631 (2018).
- Dutta, I. et al. Double Dehydrogenation of Primary Amines to Nitriles by a Ruthenium Complex Featuring Pyrazole Functionality. J. Am. Chem. Soc. 140, 8662–8666 (2018).
- Kim, J. & Stahl, S. S. Cu/nitroxyl-catalyzed aerobic oxidation of primary amines into nitriles at room temperature. ACS Catal. 3, 1652–1656 (2013).
- Lambert, K. M. et al. Metal-Free Oxidation of Primary Amines to Nitriles through Coupled Catalytic Cycles. Chem. Eur. J. 22, 5156–5159 (2016).
- Lambert, K. M. et al. Catalytic, Metal-Free Oxidation of Primary Amines to Nitriles. Org. Synth. 95, 60–79 (2018).
- Tseng, K.-N. T., Rizzi, A. M. & Szymczak, N. K. Oxidant-free conversion of primary amines to nitriles. J. Am. Chem. Soc. 135, 16352–16355 (2013).
- Ovoshchnikov, D. S., Donoeva, B. G. & Golovko, V. B. Visible-light-driven aerobic oxidation of amines to nitriles over hydrous ruthenium oxide supported on TiO2. ACS Catal. 5, 34–38 (2015).
- Wu, K. et al. Unusual lattice vibration characteristics in whiskers of the pseudo-one-dimensional titanium trisulfide TiS3. Nat. Commun 7, 12952 (2016).
- Ahammed, R. et al. ZrS3/MS2 and ZrS3/MXY (M Mo, W; X, Y S, Se, Te; X ≠ Y) type-II van der Waals hetero-bilayers: Prospective candidates in 2D excitonic solar cells. Appl. Surf. Sci. 499, 143894 (2020).
- Yi, H. et al. The electronic band structure of quasi-one-dimensional van der Waals semiconductors: the effective hole mass of ZrS3 compared to TiS3. J. Phys. Condens. Matter 32, 29LT01 (2020).
- Wang, X. et al. Highly Polarized Photoelectrical Response in vdW ZrS3 Nanoribbons. Adv. Electron. Mater. 5, 1900419 (2019).
- Tao, Y. R., Wu, X. C. & Xiong, W. W. Flexible visible-light photodetectors with broad photoresponse based on ZrS3 nanobelt films. Small 10, 4905–4911 (2014).
- Flores, E., Ares, J. R., Ferrer, I. J. & Sánchez, C. Synthesis and characterization of a family of layered trichalcogenides for assisted hydrogen photogeneration. Phys. Status Solidi Rapid Res. Lett. 10, 802–806 (2016).
- Yuan, Y. et al. Zirconium nitride catalysts surpass platinum for oxygen reduction. Nat. Mater. 19, 282–286 (2020).
- Endo, K., Ihara, H., Watanabe, K. & Gonda, S. I. XPS STUDY OF ONE-DIMENSIONAL COMPOUNDS - TIS3. J. Solid State Chem. 44, 268–272 (1982).
- Tian, Z. et al. Enhanced Charge Carrier Lifetime of TiS3 Photoanode by Introduction of S22– Vacancies for Efficient Photoelectrochemical Hydrogen Evolution. Adv. Funct. Mater., 30, 2001286 (2020).
- Wei, Y. Q., Zhou, Z. H. & Long, R. Defects Slow Down Nonradiative Electron-Hole Recombination in TiS3 Nanoribbons: A Time-Domain Ab Initio Study. J. Phys. Chem. Lett. 8, 4522–4529 (2017).
- Tian, Z. et al. Hydrogen plasma reduced black TiO2B nanowires for enhanced photoelectrochemical water-splitting. J. Power Sources 325, 697–705, (2016).
- Tian, Z. et al. Highly Conductive Cable-Like Bicomponent Titania Photoanode Approaching Limitation of Electron and Hole Collection. Adv. Funct. Mater, 28, 1803328 (2018).
- Tian, Z. et al. Novel Black BiVO4/TiO2 – x Photoanode with Enhanced Photon Absorption and Charge Separation for Efficient and Stable Solar Water Splitting. Adv. Energy Mater. 9, 1901287 (2019).
- Zhang, K. et al. Overcoming Charge Collection Limitation at Solid/Liquid Interface by a Controllable Crystal Deficient Overlayer. Adv. Energy Mater. 7, 1600923 (2017).
- Li, L. et al. Electrical transport and high-performance photoconductivity in individual ZrS2 nanobelts. Adv. Mater. 22, 4151–4156 (2010).
- KDEdKanatzidis, M. & Sutorik, A. (Karlin, KD, Ed, 1995).
- Burrard-Lucas, M. et al. Enhancement of the superconducting transition temperature of FeSe by intercalation of a molecular spacer layer. Nat. Mater. 12, 15–19 (2013).
- Hatakeda, T., Noji, T., Kawamata, T., Kato, M. & Koike, Y. New Li-Ethylenediamine-Intercalated Superconductor Lix(C2H8N2)yFe2–zSe2 with Tc = 45 K. J. Phys. Soc. Jpn. 82, 123705 (2013).
- Scheidt, E.-W. et al. Superconductivity at Tc = 44 K in LixFe2Se2 (NH3)y. Eur. Phys. J. E Soft Matter 85, 1–5 (2012).
- Yin, G. et al. Hydrogenated Blue Titania for Efficient Solar to Chemical Conversions: Preparation, Characterization, and Reaction Mechanism of CO2 Reduction. ACS Catal. 8, 1009–1017 (2018).
- Resasco, J. et al. TiO2/BiVO4 Nanowire Heterostructure Photoanodes Based on Type II Band Alignment. ACS Cent. Sci. 2, 80–88 (2016).
- Xu, Y. & Schoonen, M. A. The absolute energy positions of conduction and valence bands of selected semiconducting minerals. Am. Mineral. 85, 543–556 (2000).
- Wang, Q. et al. Oxysulfide photocatalyst for visible-light-driven overall water splitting. Nat. Mater. 18, 827–832 (2019).
- Liu, H., Xu, C., Li, D. & Jiang, H. L. Photocatalytic Hydrogen Production Coupled with Selective Benzylamine Oxidation over MOF Composites. Angew. Chem. Int. Ed. Engl. 57, 5379–5383 (2018).
- Jellinek, F., Pollak, R. & Shafer, M. X-ray photoelectron spectra and electronic structure of zirconium trisulfide and triselenide. Mater. Res. Bull. 9, 845–856 (1974).
- Wang, X. et al. Single-Atom Vacancy Defect to Trigger High-Efficiency Hydrogen Evolution of MoS2. J. Am. Chem. Soc. 142, 4298–4308 (2020).
- Sun, X. et al. Enhanced Superoxide Generation on Defective Surfaces for Selective Photooxidation. J. Am. Chem. Soc. 141, 3797–3801 (2019).
- Song, H., Wei, L., Chen, C., Wen, C. & Han, F. Photocatalytic production of H2O2 and its in situ utilization over atomic-scale Au modified MoS2 nanosheets. J. Catal. 376, 198–208 (2019).
- Lei, J. et al. Robust photocatalytic H2O2 production over inverse opal g-C3N4 with carbon vacancy under visible light. ACS Sustain. Chem. Eng. 7, 16467–16473 (2019).
There is NO Competing Interest.
- SupportingXXInformation.docx
Efficient Photocatalytic Hydrogen Peroxide Generation Coupled with Selective Benzylamine Oxidation over Defective ZrS3 Nanobelts