The synthesis of CdS hierarchical micro-nanostructures with different pore structure and their in�uence on the photocatalytic ethanol transformation

Photocatalytic ethanol conversion into high-valuable chemicals while realizing hydrogen production is attractive and challenging. In this study, ower-like, porous ower-like, and net-like CdS nanostructures were prepared by solvothermal technique and used to study the effect of morphology on ethanol conversion. It was found by characterization that the one-dimensional net-like CdS had the best crystallinity and the largest speci�c surface area, which provided more active sites and possessed superior ethanol conversion activity. The ethanol conversion was 4.7% in 10 h with a hydrogen production rate of 1.32 mmol g − 1 h − 1 and an acetaldehyde (AA) production rate of 1.96 mmol g − 1 h − 1 with a selectivity of 51%. In comparison, 2,3-butanediol(2,3-BDO) was produced at a rate of 0.61 mmol g − 1 h − 1 with a selectivity of 32%. The pore structure of one-dimensional net-like CdS with predominantly large mesopores showed better selectivity for 2,3-BDO, indicating that the pore size of the catalyst plays an important role in the C-C coupling reaction. On this basis, the catalysts were modi�ed by depositing Pt nanoparticles on net-like CdS. Both photocatalytic ethanol conversion performances of the catalysts were substantially improved.


Introduction
Bioethanol, an important biomass platform molecule, is one of the most common and renewable fuels [1,2].In this context, bioethanol reformulation is considered a promising approach for the production of high-value-added chemicals [3][4][5][6][7][8].For example, hydroxyethyl radical produced from the ethanol partial oxidation can be transferred to form 2,3-BDO or AA, which is an important raw material for the manufacture of value-added chemicals [9,10].Traditional thermal catalysis is bene cial to improve the conversion e ciency of ethanol conversion, but harsh reaction conditions and high energy consumption limit its further industrial application [10][11][12][13][14][15].Most recently, photocatalytic technology with the advantage of low energy consumption has been used to convert ethanol aqueous solution to hydrogen and highvalue products (2,3-BDO and AA) [3,5,8].
To date, some photocatalyst has been developed to convert ethanol into hydrogen and value-added chemicals.For example, Lu et al. found that the kinetics of hole-induced ethanol oxidation was very sensitive to the phase structure of TiO 2 , and a highly selective conversion of 96.6% ethanol to 2,3-BDO was achieved by adjusting the phase structure and pore size [13].Yang et al. discovered that a straightforward ligand exchange process enhanced the selectivity of 2,3-BDO from 2.6-63% by substituting the OH group on the surface of TiO 2 with NaF to control the quantity of hydroxyl radicals [16].
Bernd R. Müller et al. demonstrated that the one-hole oxidation process over nanosized ZnS catalysts produced 2,3-BDO while the two-hole oxidation process over micron-sized ZnS catalysts produced AA [17].However, the absorption of TiO 2 and ZnS to UV light limits its wide application, so it is very attractive to develop a visible-light-responsive catalyst for improving the utilization of photocatalytic ethanol conversion.
CdS with a low band gap has been widely employed for photocatalytic selective oxidation of organic compounds under visible-light irradiation [18][19][20][21].However, the low yield and selectivity of the target product limits its wide application.Many efforts have been devoted to enhancing photocatalytic activity and selectivity of CdS materials.For example, Zhou et al. found the CdS nanorods modi ed by partially reduced palladium shown 100% selectivity during photocatalytic conversion of ethanol to 1,1diethoxyethaneusing [22].Niu et al. synthesized CdS/NiS-N with a high speci c surface area using Ni-MOF-74 as a template and achieved a high yield conversion of 6.1 mmol to 2,3-BDO [23].Zhang et al. prepared Ag/CdS heterojunctions and obtained excellent H 2 and AA yields, which were 40 times higher than those of pure CdS catalysts [24].Meanwhile, the size and morphology of the catalyst usually play an important role in its performance [25][26][27][28].For instance, Xie et al. prepared CdS nanorods for methanol conversion by a solvothermal method using ethylenediamine as a solvent, and their C-C coupling properties were superior to those of nanoparticles, nanorods, and nanosheets [29].Yao et al. synthesized CdS materials that have urchin-like nano owers, branched nanowires, and fractal nanotrees morphologies for the degradation of acidic magenta, and branched CdS nanowire showed the best photocatalytic performance [30].Fang et al. synthesized various CdS morphology using solvothermal method by varying the volume of N-N dimethylformamide in the solvent, and the dendritic CdS had the best photocatalytic rhodamine degradation properties [31].However, the effect of CdS with different morphologies on the photocatalytic ethanol conversion performance has rarely been systematically investigated.
In the present study, ower-like, porous ower, and net-like CdS were synthesized by the low-temperature solvothermal method in three mixed solvents DETA, EtOH, and H 2 O with different ratios.The scanning electron microscopy (SEM), X-ray diffraction (XRD), Bruno Emmett Taylor (BET), electron paramagnetic resonance (EPR), and photoelectrochemical characterization was used to characterize the structure and properties.The net-like CdS micro-nano structure exhibited higher ethanol conversion activity and 2,3-BDO selectivity in visible light, compared to other morphology CdS samples.The excellent crystallinity and speci c surface area of one-dimensional net-like CdS structure are responsible for the attractive photocatalytic performance.Further, the greater porosity and more mesoporous structure of the catalyst CdS-N/0 favors the production of more hydroxyethyl groups, thus increasing the probability of coupling reactions.The modi cation of net-like CdS by Pt nanoparticles also signi cantly enhance the photocatalytic ethanol conversion ability.The various morphologies of CdS samples were prepared by changing the solvent ratio using the solvothermal method.Flower-like (CdS-F/0), porous ower (CdS-PF/0.2),and net-like (CdS-N/0) were synthesized by dissolving 2 mmol of cadmium acetate (Cd(CH 3 COO) 2 •2H 2 O) and 10 mmol of thiourea (NH 2 CSNH 2 ) in 60 mL of a mixture of solvents of diethylenetriamine (DETA), ethanol (EtOH), and water with the volume ratios of V DETA : V EtOH : V H2O = 2:1:0, V DETA : V EtOH : V H2O = 2:1:0.2,V DETA : V EtOH : V H2O = 2:0:1, respectively [32].After magnetic stirring for 1 h at room temperature, the solution was transferred to a 100 mL autoclave and held at 80°C for 48 h.The yellow precipitate obtained was centrifuged and then washed three times with ethanol and deionized water.
2.1.2Preparation of Pt/CdS-N/0 catalyst Pt/CdS-N/0 nanocomposites were prepared via a photoreduction process.To synthesize Pt/CdS-N/0 nanocomposites, CdS/0 (100 mg) and 1% wt H 2 P t Cl 6 solution in ethanol solution containing 5% water was pre-degassed with argon to remove any dissolved oxygen.The suspension was irradiated with a 300 W Xe lamp for 2 h.After that, the resultant product was washed with ethanol and deionized water and dried overnight at 60°C.

Catalyst Characterization
The morphology of the sample was characterized by scanning (SEM) electron microscopy (FE-SEM, TESCAN MIRA3 LMH).X-ray diffraction (XRD, Rigaku SmartLab) was used to analyze the phase and orientation of the samples using Cu Ka radiation and a scan rate of 10 min − 1 .Speci c surface (BET) areas, pore volume (Vpore), and pore diameters (Dpore) of the materials were determined by using N 2 adsorption-desorption isotherms at 77 K on a V-Sorb 2800P apparatus.The optical properties of the catalyst were analyzed by UV-Vis diffuse re ectance spectroscopy (PerkinElmer-Lambda 750 UV-Vis) with white BaSO 4 as the reference material and tested in the wavelength range of 200-800 nm.X-ray photoelectron spectroscopy (XPS) of Thermo Scienti c J Mater Sci ESCALAB 250Xi was used to further determine the elemental composition and valence state of the samples.Electron paramagnetic resonance (EPR) of captured free radicals was recorded on the Brooke EPR A 200W Spectrometer using 5,5-dimethyl-1-pyrroline-N-oxide [7].

Photocatalytic experiments
Photocatalytic experiments were performed using a closed system with an inner-irradiation-type CEL-APR reactor.Typically, the volume of the reaction solution was 50 mL, and the light source was a 300 W xenon lamp.100 mg of powdered catalyst was ultrasonically dispersed in different volumes (0%, 5%, 10%) of aqueous ethanol solution.Then, the reactor was evacuated and lled with nitrogen.During the photocatalytic reaction, the reaction system was maintained at 20°C using cooled circulating water with constant stirring to uniformly disperse the catalyst for 10 hours.A gas chromatograph (GC-950, TCD,) was employed to analyze the gas products at a pre-designed time.The composition of the liquid phase product was quanti ed by an external standard method on a chromatograph (GC-950) equipped with a ame ionization detector (FID) analyze.Ethanol conversion, productivity of product and selectivity were calculated according to the following equations: Productivitiy of product = ( 2) where n ethanol represents the molar amount of ethanol before reaction, n (e) represents the molar amount of substance of ethanol converted in 10 hours,  product represents the molar amount of the corresponding product,  catalyst represents the mass of the used catalyst.,  represents the selectivity of the corresponding product [23].

Photoelectrochemical measurement
The photoelectrochemical properties of the catalysts were analyzed with an electrochemical workstation (Aptar Automotive Laboratories, Switzerland; Nova, Waltham, MA, USA).A standard three-electrode system was carried out in this photochemical measurement, in which the reference electrode is the Ag/AgCl electrode, the counter electrode is the Pt electrode, and the working electrode is FTO (1 × 1cm − 2 ).
The electrolyte solution was 0.5 mol•L − 1 Na 2 SO 4 solution, and the reaction area was 1 cm − 2 [7] .The working electrode was prepared as follows: 5 mg catalyst was dispersed in a mixed solution that contained 1 mL of N-N-dimethylformamide (DMF) and 2 mL of ethanol, and the mixture was sonicated for 2 h to form a homogeneous solution.After that the solution was dropped in the FTO region controlled with paper tape and dried at 60°C.The analysis methods include transient photocurrent response plots (It), photocurrent at 0.598V and chemical impedance spectroscopy (EIS) under a 300 W Xenon lamp irradiation.

Results and discussion
3.1 Structure and morphology of the materials

The SEM characterization
The type, ratio, and diffusion behavior of the solvent have a large in uence on the catalyst morphology [33,34].Figure 1 shows the SEM images of the catalyst generated at three-volume ratios of DETA, E t OH, and H 2 O.As shown in Fig. 1a and d, the CdS-F/0 samples exhibit ower-like structures when DETA and EtOH were used as solvents with a volume ratio of 2: 1, and each ower is constructed of several assembled nanosheets [32].After adding H 2 O (V DETA : V EtOH : V H2O =2:1:0.2) to the reaction system, it was found that macropores appeared in the lamellar units forming the owers, which resulted in the formation of a porous ower micro-nanostructure (Figs.1b and e).However, net-like CdS micronanostructures were observed in the CdS-N/0 samples shown in Figs.1c and f, without the addition of ethanol (V DETA : V EtOH : V H2O =2:0:1).
3.1.2X-ray diffraction and X-ray photoelectron spectroscopy analysis  110), (103), and (112), respectively.When the solvents are DETA and EtOH, the CdS-F/0 samples show high intensity in the (002) peak and broad peaks for other XRD lines, which implies higher crystallinity along the c-axis and poorer crystallinity in the x-y plane, resulting in a two-dimensional owerlike morphology [35][36][37].Furthermore, as the proportion of water in the solvent gradually increases, the relative strength of the (002) plane to the sum of the (100) and (101) planes decreases, and crystallization occurs in the x-y plane and is preferentially oriented along the c-axis [34].The calculated results are shown in Table 1 (CdS-F/0 > CdS-PF/0.2> CdS-N/0), and the morphology of the catalysts realizes the transition from two-dimensional ower to one-dimensional net-like.The peak intensity of the crystals gradually increases during the transition from the ower-like to the net-like morphology.The morphology growth mechanism will be covered in further detail in the growth mechanism section below.The composition and elemental chemical states of CdS-N/0 nanomaterials were further analyzed by XPS.
Figure 2b displays the full spectrum of CdS-N/0, no other elements were found, except for the Cd, S, O, and C. The Fig. 2c-d   Figure 3 depicts typical nitrogen adsorption-desorption isotherms and pore size distribution curves for the prepared catalysts with different morphology [40].All isotherms have a type IV (Brunauer-Deming-Deming-Teller (BDDT) classi cation) form and are mesoporous materials [41].It can be observed from Table 2 that the speci c surface area of samples CdS-F/0, CdS-PF/0.2,and CdS-N/0 ranges from 43.4 m 2 g -1 to 157.9 m 2 g -1 .Meanwhile, as shown in Fig. 3a, the isotherm of CdS-N/0 shifted higher in the low P/P 0 range (0.2), indicating a larger speci c surface area of sample CdS-N/0, compared with CdS-F/0 and CdS-PF/0.2samples [42].The pore distributions of the as-synthesized materials covered a wide range from 2 to 100 nm, as shown in Fig. 3b.The CdS-F/0 and CdS-PF/0.2samples had the highest number of pores with a size of about 5 nm, and the number of pores decreased slowly with the increase of pore size.A large number of distributions in the range of 5-50 nm and 5-100 nm appear in CdS-F/0 and CdS-PF/0.2,respectively.In contrast, the pores of CdS-N/0 are mainly concentrated at around 18 nm and distributed between 2-71 nm.Moreover, combined with the nitrogen adsorption-desorption isotherm, CdS-N/0 samples show hysteresis loops at high relative pressures close to unity, indicating the formation of large mesopores and macropores [42].

Morphology growth mechanism
The possible growth mechanisms for CdS-F/0, CdS-PF/0.2,and CdS-N/0 catalysts are depicted in Fig. 4.
For the oxygen-free solvent DETA, the contained N atoms are triple-coordinated and smaller than the C atoms.Therefore, the N atoms in the current solvent can bond with the exposed Cd atoms on the (100) and (010) surfaces, thus controlling the growth of the (100) and (010) surfaces.The number of N 3C atoms in the solvent molecule and the length of the atomic chain determine the morphology and dispersion of CdS [42].However, a single DETA solvent is highly viscous and the CdS samples tend to grow into a massive structure, which is unfavorable for dispersion.Therefore, it is necessary to introduce a mobile co-solvent, water or ethanol, into the solvothermal system [32].Due to the attraction of N atoms to H + in the chemical equation, the DETA solution is weakly basic.It can be further concluded that if H 2 O is present in the mixed solvent thermal system, the attraction of N-Cd decreases due to the equilibrium between N-Cd and N-H + .During the formation of CdS-F/0, due to the absence of water in the solvent, the growth of the (100) and (010) crystallites is maximally inhibited in the presence of only N-Cd, while the orientation of the (002) crystallites reach an optimal level, forming a ower-like morphology consisting of nanosheets grown by C-axis extension.Upon addition of water, N-H + promotes the growth of some of the (100) and (010) crystalline planes and decreases the orientation of the (002) crystalline planes, which leads to the formation of large holes in the nanosheets due to the growth of the x-y plane thereby leading to the formation of a porous ower morphology.In the absence of ethanol participation, the CdS crystals will preferentially grow along the (002) direction and terminate at the (100) or (010) surface to form a well-dispersed net-like structure.

Photocatalytic Performance of CdS Nanoarchitectures
Different morphologies of CdS were used for photocatalytic dehydrogenation coupling of ethanol.H 2 , AA, and 2,3-BDO as the main products were formed during 10h of visible light irradiation using CdS as photocatalysts in 5 vol% ethanol solution.As shown in Fig. 5a, the ethanol conversion of CdS-F/0, CdS-PF/0.2,and CdS-N/0 catalysts were 1.57%, 3.6%, and 4.7% respectively.Figure 5b exhibited the hydrogen production rates of the catalysts, it was found that the hydrogen production amount of all CdS samples gradually increased with the reaction time, and CdS-N/0 has the best photocatalytic hydrogen production rates of about 1.32 mmol g − 1 h − 1 .Figure 5c presents the production rates of 2,3-BDO and AA computed using the external standard method.The 2,3-BDO and AA yields of CdS-N/0 with larger speci c surface area and better crystallinity were 0.61 mmol g − 1 h − 1 and 1.96 mmol g − 1 h − 1 , respectively, which were better than those of the CdS-F/0 and CdS-PF/0.2samples.The selectivity of 2,3-BDO and AA was analyzed in Fig. 5d.CdS-F/0, CdS-PF/0.2,and CdS-N/0, and exhibit selectivities towards 2,3-BDO at 12%, 27%, and 32%, respectively.This may be due to their different pore size distributions as shown in Fig. 3b.
To investigate the impact of water content in solvents on photocatalytic performance, a control experiment was conducted using CdS-N/0 photocatalyst in ethanol solutions with different water content, as shown in Fig. 6.Figures 6a and b illustrate the photocatalytic performance of CdS-N/0 catalysts for the conversion of ethanol at different water contents.The photocatalytic performance of the catalyst is weak in pure ethanol solution.When 5 vol% of water was added, the conversion performance of ethanol was signi cantly improved, especially the hydrogen production was sharply increased, which was mainly because water as an electron sacri cer was able to consume a large number of electrons, effectively inhibiting the electron-hole pair complexation so that more holes were involved in the oxidation process of ethanol.And the hydroxyl radicals generated by hole oxidation form hydrogen bonds with water, which facilitates the desorption of the generated hydroxyethyl radicals from the catalyst surface and increases the possibility of C-C coupling.When 10 vol% water is introduced, the quantity and structure of hydrogen bonds change, complicating the coupling process and lowering photocatalytic e ciency.The selectivity of the coupling reaction to produce 2,3-BDO in an ethanol solution containing 5 vol% of water is also superior to other ratios of water, as shown in Fig. 6b.

The light absorption and photoelectrochemical performance of the prepared samples
To better evaluate the photocatalytic e ciency, the optical properties of CdS with different morphologies were investigated using UV-Vis diffuse re ectance spectroscopy.As show in Fig. 7a, the evident and narrow absorption edges show good visible light absorption [32].Figure 7b shows the converted plots based on the Kubelka-Munk function vs. photon energy, from which the bandgap (Eg) energy of CdS-F/0, CdS-PF/0.2,and CdS-N/0 can be roughly estimated to be 2.33, 2.31, and 2.36 eV, respectively [43].The band gaps of the sample CdS are all slightly redshifted compared to the bulk CdS (2.42 eV) [44].
Comparison of hydrogen production, 2,3-BDO, and AA yields of CdS samples (Fig. 5) with the optical properties of similar bandgap values (Fig. 7) reveals that nanomaterials with similar bandgaps exhibit different properties, which may be related to the nanomorphology of the catalysts [25].
The photoelectrochemical method was used to evaluate the separation e ciency of photogenerated electrons and holes.Figure 7c-d shows the transient photocurrent density curves and electrochemical impedance spectroscopy (EIS) of the as-prepared CdS-F/0, CdS-PF/0.2,and CdS-N/0 samples.As shown in Fig. 7c, CdS-F/0 exhibits a relatively weak photocurrent response due to the severe recombination of photogenerated electron-hole pairs.CdS-N/0 showed the highest photocurrent response, resulting in excellent light-induced electrical performance.Figure 7d shows that the arc radii of the CdS-N/0 sample is the smallest, indicating the bene ts of the Photocatalytic performance [43].Therefore, the onedimensional net-like morphology of CdS-N/0 catalysts can promote the separation and transfer of photogenerated charges, which can effectively improve photocatalytic performance.

Mechanism of photocatalysis
By investigating the effect of water content in the solution on the conversion of ethanol, the hydrogen production rate during the reaction of an ethanol solution with a water content of 5 vol% spiked as compared to the pure ethanol solution, suggesting that the water in the solution consumed most of the photogenerated electrons for the precipitation of hydrogen.CdS catalysts are incapable of generating hydroxyl radical actives.Thus, the actives that play a role in ethanol oxidation are photogenerated vacancies [45].The αC-H bond in ethanol was oxidized to form •CH(OH)CH 3 , and the hydrogen bond formed between the hydroxyl radical and the hydroxyl group of water and the pore structure of the CdS-N/0 catalyst, which was dominated by large mesopores, promoted the desorption of •CH(OH)CH 3 from the surface of the catalyst, which greatly enhanced the possibility of the coupling reaction to produce 2,3-BDO.The hydroxyethyl group which could not be desorbed in time was further oxidized by the holes to other by-products such as acetaldehyde and acetic acid.The reaction process is identical to that shown in Scheme 1.
From the photocatalytic experimental data of the photocatalysts prepared in the above experiments, it can be seen that the photocatalytic performance of the photocatalysts prepared with CdS-N/0 is much higher than that of other morphologies photocatalysts.As far as the light absorption performance of CdS catalysts is concerned, the change in morphology has little effect on the light absorption performance of the catalysts.The excellent photocatalytic performance of CdS-N/0 is mainly attributed to i) the unique one-dimensional structural morphology of CdS-N/0 with a larger speci c surface area than other morphologies, which provides more active sites for ethanol conversion; and ii) the better crystallinity and stronger photocurrent intensity of CdS-N/0, which suggests that the photogenerated carriers can be separated better than those of other CdS samples, which is more conducive to the ethanol conversion.Therefore, we conclude that the one-dimensional CdS-N/0 morphology with a larger speci c surface area is favorable for photocatalytic ethanol conversion and has the best photocatalytic performance.
At the same time, CdS-N/0 has relatively excellent 2,3-BDO selectivity.From its pore size distribution diagram, it can be concluded that the most available pore size of CdS-F/0 is about 5 nm, and the number of pores decreases slowly with the increase of pore size, with a larger percentage of pores in the 5 nm-50 nm range.Compared with CdS-F/0, the pore distribution in CdS-PF/0.2 is concentrated in the range of 5 nm-100 nm, with a higher number of mesopores and the presence of some macropores.The most available pore size of CdS-N/0 is 18 nm and the percentage of pores from 18 nm to 71 nm is the maximum.We assume that the structure of the CdS-N/0 samples with a larger percentage of large mesopores may offer more possibilities for the formation of 2,3-BDO by coupling reactive [13].In parallel, we also investigated the number of hydroxyethyl groups produced by CdS samples by electron spin resonance (EPR) spectroscopy using 5,5-dimethyl 1-pyrroline-N-oxide (DMPO) as a spin-trapping agent(Fig.8).The number of hydroxyethyl radicals produced by the CdS samples was proportional to the selectivity of 2,3-BDO.The correlation between the C-C coupling reaction and the pore size of the catalyst was further demonstrated.

Modi cation of photocatalytic performance
Platinum nanoparticles act as reducing co-catalysts that utilize light-generated electrons to reduce H + and generate H 2 , thus making it easier to separate and utilize photogenerated carriers [46].As shown in Fig. 9, the photodeposition of platinum nanoparticles on CdS-N/0 catalysts signi cantly improves the photocatalytic ethanol conversion performance.The ethanol conversion rate is 16.14%.As shown in Fig. 9a the yield of various products has increased by nearly 3.5 times, with 2,3-BDO yielding 2.64 mmol g − 1 h − 1 , AA yielding 6.42 mmol g − 1 h − 1 , and H 2 yielding 5.45 mmol g − 1 h − 1 .As shown in Fig. 9b, the selectivity of the various products remains essentially unchanged compared to CdS-N/0. Figure 9c and d shows the stability of the photocatalytic performance of the Pt/CdS-N/0 catalyst.It can be seen that the yields of the products were basically consistent during the three stability cycle tests.The photocatalytic performance of the catalyst only marginally diminished in the third cycle, which was attributed to the photo corrosion phenomena of the CdS catalyst itself.Figure 9d depicts the product selectivity throughout the catalyst stability test, and it can be seen that the product selectivity remained essentially unchanged during the three cycles of the test.
Based on the photocatalytic properties of the photocatalysts in the previous experiments, it can be determined that the better the crystallinity of the different morphologies of the photocatalysts, the larger the speci c surface area, the better the separation of photogenerated carriers, and the better the ethanol conversion performance.The presence of large-sized pores promotes the selectivity of the C-C coupling reaction.

Conclusion
In summary, we have successfully prepared cadmium sul de nanostructures with different morphologies for photocatalytic ethanol conversion using a low-temperature solvothermal method.It was found that the photocatalytic performance of CdS with well-crystallized and large speci c surface area morphology was better than other morphologies.The rate of hydrogen production was 1.32 mmol g − 1 h − 1 , and the rate of acetaldehyde production was 1.96 mmol g − 1 h − 1 ; the rate of 2,3-BDO production was 0.61 mmol g − 1 h − 1 .The selectivity of 2,3-BDO is mainly related to the pore size distribution of the catalyst, and the large pore size pore structure is more favorable for the desorption of hydroxyethyl radicals, which in turn improves the selectivity of 2,3-BDO.The CdS-N/0 catalyst was dominated by large pore-size mesopores and macropores, corresponding to the highest 2,3-BDO selectivity (32%).On this basis, we loaded Pt nanoparticles onto CdS-N/0 catalysts by photodeposition, and the ethanol conversion as well as the hydrogen production e ciency were greatly improved.

Figure 1 The
Figure 1

Figure 5 Conversion
Figure 5

Figure 7 The
Figure 7

Table 1
Structural properties of CdS nanostructures determined from XRD data.

Table 2
Band gap of catalysts with different morphologies.BET surface-area and pore volume (V pore ) and average pore diameter (D pore ), were determined from N 2 physisorption.