Photocatalytic Hydrogen Evolution Reaction Activity Research Articles

HER activity of nanosheets of 2D solid solutions of MoSe2 with MoS2 and MoTe2

MoSxSe(2−x) and MoSexTe(2−x) solid solutions with various S:Se and Se:Te ratios have been prepared by high temperature solid-state reactions, and thinned down to few-layers by Li-intercalation followed by exfoliation. Photocatalytic as well as electrocatalytic hydrogen evolution reaction (HER) activity of exfoliated MoSxSe(2−x)/MoSexTe(2−x) 2D nanosheets have been studied. It is found that Se-rich compositions exhibit good HER activity. The MoS0.5Se1.5 nanosheets show high photocatalytic HER activity yielding 29.6 mmol h−1 g−1 of H2, while MoS1.0Se1.0 displays good electrocatalytic activity with an onset potential of −0.220 V. Amongst MoSexTe(2−x) solid solutions, MoSe1.8Te0.2 shows relatively high photocatalytic HER activity (5.0 mmol h−1 g−1), while MoSe1.0Te1.0 exhibits a low onset potential (−0.190 V vs. RHE).

Facile construction of O-doped crystalline / non-crystalline g-C3N4 embedded nano-homojunction for efficiently photocatalytic H2 evolution

Realizing the efficient utilization of photogenerated carriers is a pivotal process to access the efficient transformation of light energy. Herein, we firstly practice a facile template method to synthesize O-doped crystalline/none-crystalline g-C3N4 embedded nano-homojunction photocatalysts (CMCCN-x). This nano-homojunction makes the crystalline phase sufficiently contact with amorphous phase and further facilitates the photoinduced electron transformation. Therefore, the best performance catalyst CMCCN-5 well integrates the advantages of crystal g-C3N4 and amorphous g-C3N4, which exhibits an excellent photogenerated carrier separation ability and abundant photocatalytic hydrogen evolution reaction activity sites. Excellent performance in the separation and use of photogenic carriers endows CMCCN-5 with efficient utilization of photogenerated carriers. Although there is a limited light absorption range (<460 nm), the photocatalytic hydrogen evolution rate of CMCCN-5 is up to 203.66 μmol h−1 under the visible light irradiation, about 86 times higher than pristine g-C3N4. The AQY numbers of CMCCN-5 at 420 nm and 450 nm are up to 26.9% and 14.0%, respectively. Thus, the significant effectiveness is forcefully proved for the facile construction of O-doped g-C3N4 crystalline/none-crystalline nano-homojunction.

Ring-Shaped Polyoxometalate Built by {Mn 4 PW 9 } and PO 4 Units for Efficient Visible-Light-Driven Hydrogen Evolution

A novel mixed-valence, ring-shaped multinuclear Mn-containing polyoxometalate, [H2N(CH3)2]15NaH8-[MnIII3MnIV(μ3-O)3(OAc)PO4(B-α-PW9O34)]4·36H2O (1) was made and systematically characterized using v...

Amidine/Amidinate Cobalt Complexes: One-Pot Synthesis, Mechanism, and Photocatalytic Application for Hydrogen Production.

A new synthetic route was carried out via a one-pot reaction to prepare a novel series of amidine/amidinate cobalt complexes 8-10 by mixing ligand 2 (6-pyridin-2-yl-[1,3,5]-triazine-2,4-diamine) with Co(II) in acetonitrile or benzonitrile. We observed that a change of solvent from methanol (used in complex 7, previously reported) to nitrile solvents (MeCN and PhCN) led to the in situ incorporation of the amidine group, ultimately forming 8-10. So far, this is a unique method reported to introduce amidine/amidinate groups into a pyridinyl-substituted diaminotriazine complex. Remarkably, the single crystal X-ray diffraction study (SCXRD) of these new compounds reveals associations involving Janus DATamidine and Janus DATamidinate. A mechanism is proposed to explain the formation of amidine/amidinate groups by investigating the single crystal structures of the possible intermediates 11 and 12 where the cobalt ion acts as a template. These amidine/amidinate cobalt complexes were used as a model to assess the photocatalytic activity for the hydrogen evolution reaction (HER). Complexes 9 and 10 show a 74% and 86% enhancement, respectively, of the catalytic activity towards the HER compared to complex 7. This highlights the structure-property relationship. By examining the novel cobalt complexes described here, we discovered the following: (i) a method to introduce an amidine group into a pyridine DAT-based complex, (ii) the efficiency of amidine complexes to form multiple hydrogen bonds to direct the molecular organization, (iii) the plausible mechanism of formation of amidines based on the SCXRD study, (iv) the modification of the final structure and hence the final properties by varying the reaction conditions, and (v) the utility of amidine complexes towards photocatalytic HER activity.

Ultrafine nano 1T-MoS2 monolayers with NiOx as dual co-catalysts over TiO2 photoharvester for efficient photocatalytic hydrogen evolution

Molybdenum disulfide (MoS2) of 1 T phase was found to potentially replace Pt as efficient co-catalyst for the hydrogen evolution reaction (HER). Herein, an ultrafine nano 1 T-MoS2 monolayer of around 10 nm was successfully synthesized and showed a high electrocatalytic HER activity with low overpotential of 78 mV at 10 mA cm−2. When the 1 T-MoS2 is loaded onto P25 TiO2, its ultrafine size dramatically promotes the superior interface bonding with TiO2 and a high photocatalytic HER activity of 300.3 μmol h−1 is obtained. Furthermore, a strategy by introducing NiOx co-catalyst into the 1 T-MoS2/P25 to fabricate a dual co-catalyst composite 1 T-MoS2/P25/NiOx significantly improves the photocatalytic HER activity to 1629.1 μmol h-1 which is very close to Pt/P25 of 2196.8 μmol h-1. The close interface-bonding between the nanosized 1 T-MoS2 monolayer and P25 along with the assistance of NiOx results in the superior photocatalytic HER activity by the enhanced separation and transfer of the photogenerated electrons and holes.

Visible‐Light‐Induced Photochemical Hydrogen Evolution and Degradation of Crystal Violet Dye by Interwoven Layered MoS2/Wurtzite ZnS Heterostructure Photocatalyst

AbstractThe photocatalytic properties of a material predominantly depend upon the material fabrication. In the last few years, sulfide based nanomaterials were used for their extraordinary efficiency due to their structural and morphological features. Present work is focused on the preparation of bimetallic layered molybdenum‐wurtzite zinc sulfide heterostructure by facile hydrothermal method. The prepared MoS2−ZnS was characterized by X‐ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Brunauer‐Emmett‐Teller (BET) surface analysis and X‐ray photoelectron spectroscopy (XPS). MoS2−ZnS showed high photocatalytic hydrogen evolution reaction (HER) and dye degradation compared to pure ZnS and MoS2. The synergistic effect of layered MoS2 and wurtzite ZnS would have amplified the photocatalytic HER activity and degradation of crystal violet dye under visible light irradiation; the electron‐hole recombination was significantly reduced due to the heterostructured arrangement of MoS2‐ wurtzite ZnS

MoSx Coated Copper Nanowire on Copper Foam as A Highly Stable Photoelectrode for Enhanced Photoelectrocatalytic Hydrogen Evolution Reaction via. Plasmon-Induced Hot Carriers

We prepared a three dimensional (3D) hierarchical porous structure with a MoSx coated copper nanowires on copper foam (Cu NWs@MoSx/Cu foam) and explored the photoelctrocatalytic activity toward hydrogen evolution reaction (HER). The optical behavior of the Cu NWs@MoSx/Cu foam resulted from the photoinduced charge-carriers of Cu NWs/Cu foam due to surface plasmon resonance (SPR) effect. Cu NWs@MoSx/Cu foam-20c displays an enhanced absorption intensity within the visible region and the increased separation of charge-carriers due to cooperative interactions between plasmonic copper and MoSx. The photocatalytic HER activity of Cu NWs@MoSx/Cu foam-20c is featured with H2 production of 857.4 μmol g−1h−1. The photocurrent ΔJ of Cu NWs@MoSx/Cu foam-20c is 13.7 times that of the MoSx/FTO-20c, 7.0 times that of the Cu foam@MoSx-20c and 1.5 times that of the Cu NWs/Cu foam. More importantly, Cu NWs@MoSx/Cu foam-20c remained almost unchanged in microstructure or composition and photoelectrocatalytic performance after over 56 h testing, suggesting its superb stability. This is ascribed to the binder-free electrode and the formation of the Cu1.83Mo3S4 composite at the interface between Cu NWs and MoSx. This highly stable and active photoelectrode will provide a promising perspective for photoelectrocatalytic H2 production.

Phosphorus-doped polymeric carbon nitride nanosheets for enhanced photocatalytic hydrogen production

Photocatalytic hydrogen production by water splitting is one of the most effective strategies for solar energy conversion and utilization. The metal-free polymeric carbon nitride (CN) has been widely used as an efficient photocatalyst for the photocatalytic hydrogen evolution reaction (HER). However, to date, the solar to hydrogen conversion efficiency of the CN-based photocatalysts is still low. Herein, to boost the photocatalytic activity of CN, controllable phosphorus atoms were introduced to form P-doped CN (PCN) via an evacuated ampoule calcination strategy. Compared with bare CN, the optimized PCN exhibits remarkably enhanced photocatalytic HER activity, with the HER rate up to 261.2 µmol h−1 and 171.6 µmol h−1 under the simulated solar light and visible-light illumination, respectively. It was revealed that the boosted photocatalysis for HER is mainly ascribed to the P dopants that can synergetically increase the visible-light absorption and facilitate the charge transfer process. This present work highlights improving the photocatalytic energy conversion efficiency by controllable tuning of the heteroatom doping degree in photocatalysts.

Strongly coupled 2D-2D nanojunctions between P-doped Ni2S (Ni2SP) cocatalysts and CdS nanosheets for efficient photocatalytic H2 evolution

Developing low-cost, environment-friendly and highly-active nanocomposites for photocatalytic hydrogen evolution reaction (HER) holds pivotal function in water splitting. Supported cocatalysts on semiconductor can facilitate speedy transfer and separation of photoexcited charge, active interfacial response and suppress photocorrosion. We, for the first time, proposed a novel strategy to formed 2D-2D (two dimensional) nanocomposites by loading 2D P-doped Ni2S (Ni2SP) cocatalysts onto 2D CdS nanosheets (NSs). The as-obtained 2D-2D CdS/Ni2SP nanocomposites exhibited excellent HER activity in 0.25 M Na2S-Na2SO3 sacrificial solution under visible light (λ ≥ 420 nm). The optimal loading of 2 wt% 2D Ni2SP on 2D CdS as a cocatalyst yielded an optimal H2 production rate at 18.96 mmol g−1 h−1, which was approximately 3.26 folds higher than that of bare 2D CdS (5.82 mmol g−1 h−1) without cocatalysts. In the presence of non-precious metal, the highest apparent quantum efficiency of 4.8% was recorded at 420 nm. The enhanced photocatalytic HER activity was attributed to the excellent interfacial coupling effects of Ni2SP NSs cocatalyst with CdS NSs, which was essential for the rapid charge separation and transfer, increased number of active sites and improved H2-evolution kinetics. This study offers a feasible scheme to design efficient photocatalysts system to produce hydrogen.

Superlattices of covalently cross-linked 2D materials for the hydrogen evolution reaction

Amongst the recent developments in 2D materials, van der Waals heterostructures formed by depositing a monolayer or few-layers of a 2D material on a monolayer or on few-layers of the same or another 2D material have attracted great attention. As an alternative to such heterostructures, we have carried out investigations on covalently cross-linked heterostructures by chemical coupling of layers of the same or different 2D materials. This effort has met with success, with typical systems studied by us being graphene–graphene, graphene–MoS2, C3N4–MoS2, borocarbonitride–MoS2, and phosphorene–MoS2. We describe these structures to demonstrate how the covalent cross-linking strategy yields novel 2D nanocomposites. These structures exhibit interesting gas adsorption properties as well as noteworthy hydrogen evolution reaction (HER) activity. The phosphorene–MoS2 nanocomposite is found to exhibit superior photocatalytic HER activity. The most interesting nanocomposite is BCN–MoS2 which exhibits electrochemical HER activity comparable to platinum, thus providing a new and novel example of metal-free catalysis.

Precursor-Engineering Coupled Microwave Molten-Salt Strategy Enhances Photocatalytic Hydrogen Evolution Performance of g-C3 N4 Nanostructures.

A precursor-engineering strategy coupled with a microwave molten-salt process (PE-MWMS) is developed to synthesize graphitic carbon nitride (g-C3 N4 ) with an isotype triazine/heptazine-based g-C3 N4 heterojunction as a photocatalyst for the hydrogen evolution reaction (HER) under visible light illumination. Four hybrid precursor combinations-thiourea/melamine, thiourea/dicyandiamide, urea/melamine, and urea/dicyandiamide-are used to synthesize g-C3 N4 heterojunctions by the PE-MWMS process. Control experiments indicate that the precursor components and microwave treatment have a great effect on the HER performance of the g-C3 N4 samples. Samples synthesized with the optimal molar ratios of thiourea/melamine (2:1), thiourea/dicyandiamide (2:1), urea/melamine (3:1), and urea/dicyandiamide (3:1), exhibit the highest HER rates of 3135, 2519, 2844, and 2565 μmol g-1 h-1 , respectively. The amounts of heptazine and triazine units in the g-C3 N4 samples can be easily adjusted by changing the ratios of the hybrid precursors and play a decisive role in improving the photocatalytic HER activity. Because of the unique composition and microstructure, the efficient separation of electron-hole pairs, the broadened photo-absorption edges, and the narrowed band gaps, the as-obtained triazine/heptazine-based g-C3 N4 nanostructures exhibit promising activity for HER application.

Internal-Field-Enhanced Charge Separation in a Single-Domain Ferroelectric PbTiO3 Photocatalyst.

Ferroelectric materials with spontaneous polarization-induced internal electric fields have drawn increasing attention in solar fuel production due to the intrinsic polarized structure. However, the origination of charge separation in these materials at the nano/microlevel is ambiguous owing to the complexity of the multielectric fields. Besides, the observed charge separation ability is far from theoretical expectation. Herein, by spatially resolved surface photovoltage spectroscopy, it is clearly demonstrated that the depolarization field in single-domain ferroelectric PbTiO3 (PTO) nanoplates is the main driving force for charge separation and it can effectively drive photogenerated electrons and holes to the positive and negative polarization facets, respectively. Moreover, the charge separation ability of PTO nanoplates increases with increasing particle size along the polarization direction, due to the increasing potential difference between the opposite polarization facets. Furthermore, this driving force for charge separation directly contributes to the enhancement of the photocatalytic hydrogen evolution reaction activity in ferroelectrics. Finally, it is proved that the screening field compensates part of the depolarization field and can be diminished by adding a dielectric layer on the ferroelectric surface. These findings demonstrate the importance of increasing the depolarization field and decreasing the screening field for efficient charge separation in ferroelectric semiconductor photocatalysts.

Photocatalytic hydrogen evolution reaction activity comparable to 1-D nanofiber materials exhibited by the kesterite nanorods catalysts

Copper-based earth-abundant chalcogenides (kesterite) such as Cu2CoSnS4 and Cu2NiSnS4 are important class due to their outstanding performance and earth-abundant composition. Here, we have successfully synthesized Cu2CoSnS4, Cu2NiSnS4 and Cu2ZnSnS4 nanorods by a hot-injection technique. The photocatalytic hydrogen production activities of rod-like Cu2XSnS4 (X = Co, Ni and Zn) catalysts have been investigated by using electron donor triethanolamine and photosensitizer eosin-Y under visible-light irradiation. The hydrogen evolution rates for the nanorods change in the order of Cu2NiSnS4> Cu2CoSnS4> Cu2ZnSnS4 (5117 μmolg−1h−1, 1342 μmolg−1h−1 and 719 μmolg−1h−1) respectively. The hydrogen evolution activities of Cu2XSnS4 nanorods have been compared to that of nanofiber and nanodot forms of Cu2XSnS4 catalysts. Cu2XSnS4 nanorods have been showed comparable photocatalytic activity for the hydrogen evolution compared with 1-D nanofiber Cu2XSnS4 catalysts.

Theoretical calculations and controllable synthesis of MoSe2/CdS-CdSe with highly active sites for photocatalytic hydrogen evolution

It is still of great practical significance to exploring low-cost and earth-abundant alternative materials as cocatalyst for photocatalytic hydrogen evolution. The density functional theory (DFT) calculations indicated that both the basal plane and the edge of mixed phase MoSe2 provide the highly catalytic activity for hydrogen evolution reaction (HER). Based on this, the mixed phase MoSe2 was designed as an excellent cocatalyst because of superior ability to receive electrons and optimal active sites for HER. Herein, the ternary (1T/2H) MoSe2/CdS-CdSe structure was prepared by a simple hydrothermal method. The hydrazine monohydrate as reductant helps to control 1T phase content of MoSe2, and the maximum content of 1T phase MoSe2 reaches 66.5%. The results showed that the H2 evolution rate of the optimized MoSe2/CdS-CdSe reached a value of 24.34 mmol h−1 g−1 and a high quantum efficiency (QE) of 28.5% at 500 nm. A volcano-like correlation has been presented for the first time to illustrate the effect of structures of MoSe2 on photocatalytic activity for HER, which provides the direction of design of MoSe2 cocatalyst.

Carrier-Selective Blocking Layer Synergistically Improves the Plasmonic Enhancement Effect.

Plasmonic enhancement is a versatile and convenient way to enhance the conversion efficiency of various photoenergy conversion systems, such as photocatalysts and solar cells. We refine a plasmonic enhancement system by focusing on a carrier blocking layer (between a plasmonic metal and a photoactive layer), which is commonly used to prevent a major quenching channel in a plasmonic enhancement system. The hydrogen evolution reaction (HER) activity is enhanced by 33 times from the introduction of a carrier-selective blocking layer (CSBL) in Ag-CdS nanoparticles. The Ag2S layer, a typical example of a CSBL, synergistically improves the plasmonic enhancement effect of Ag on the photocatalytic HER activity of CdS by both the selective blocking of photoexcited electrons and the effective transfer of holes, which extends the lifetime of the active species (electrons in the conduction band) in the semiconductor photocatalyst (CdS) to accelerate the photocatalytic HER. We propose a new strategy for a further improvement of plasmonic enhancement systems.

Remarkable photochemical HER activity of semiconducting 2H $$\hbox {MoSe}_{{2}}$$ MoSe 2 and $$\hbox {MoS}_{{2}}$$ MoS 2 covalently linked to layers of 2D structures and of the stable metallic 1T phases prepared solvo- or hydro-thermally $$^{\S }$$ §

$$\hbox {MoS}_{{2}}$$ and $$\hbox {MoSe}_{{2}}$$ in the stable semiconducting 2H form show negligible photocatalytic activity for the hydrogen evolution reaction (HER). By linking the layers of the dichalcogenide with layers of other 2D materials such as carbon-rich borocarbonitride ( $$\hbox {BC}_{{7}}\hbox {N}$$ ), one can enhance the photochemical HER activity significantly. Interestingly, such nanocomposites, $$\hbox {MoSe}_{{2}}$$ – $$\hbox {MoSe}_{{2}}$$ and $$\hbox {MoSe}_{{2}}$$ –BCN show high photocatalytic activity even though the dichalcogenide itself is in the 2H form. This study shows the important role played by covalent cross-linking of layered compounds. Photocatalytic activity of covalently cross-linked layer of 2H- $$\hbox {MoSe}_{{2}}$$ is higher than that of 2H- $$\hbox {MoS}_{{2}}$$ . Unlike the 2H forms, the metallic 1T forms of $$\hbox {MoS}_{{2}}$$ and $$\hbox {MoSe}_{{2}}$$ prepared by lithium intercalation followed by exfoliation, exhibit high photocatalytic HER activity. Unfortunately, materials prepared by lithium intercalation are unstable. The 1T forms of $$\hbox {MoSe}_{2}$$ and $$\hbox {MoS}_{{2}}$$ prepared by solvothermal or hydrothermal methods are, however, quite stable and exhibit good photochemical activity for HER. The 1T forms are generally superior to the covalently linked 2H forms. The present study shows how $$\hbox {MoSe}_{{2}}$$ and $$\hbox {MoS}_{{2}}$$ in both 2H and 1T forms can be exploited for photochemical HER activity by appropriate chemical manipulation. SYNOPSIS Photocatalytic HER activity of 2H- $$\hbox {MoSe}_{{2}}$$ covalently linked with other 2D layered materials is superior to that of the pristine sheets. 1T-forms of $$\hbox {MoSe}_{2}$$ and $$\hbox {MoS}_{{2}}$$ grown by solvothermal or hydrothermal method show good photochemical activity. The present study shows that both $$\hbox {MoSe}_{{2}}$$ and $$\hbox {MoS}_{{2}}$$ in either 2H or 1T form can be exploited for photochemical HER activity by suitable chemical and physical manipulation.

An Efficient, Visible‐Light‐Driven, Hydrogen Evolution Catalyst NiS/ZnxCd1−xS Nanocrystal Derived from a Metal–Organic Framework

AbstractPhotocatalytic water splitting for hydrogen production using sustainable sunlight is a promising alternative to industrial hydrogen production. However, the scarcity of highly active, recyclable, inexpensive photocatalysts impedes the development of photocatalytic hydrogen evolution reaction (HER) schemes. Herein, a metal–organic framework (MOF)‐template strategy was developed to prepare non‐noble metal co‐catalyst/solid solution heterojunction NiS/ZnxCd1−xS with superior photocatalytic HER activity. By adjusting the doping metal concentration in MOFs, the chemical compositions and band gaps of the heterojunctions can be fine‐tuned, and the light absorption capacity and photocatalytic activity were further optimized. NiS/Zn0.5Cd0.5S exhibits an optimal HER rate of 16.78 mmol g−1 h−1 and high stability and recyclability under visible‐light irradiation (λ&gt;420 nm). Detailed characterizations and in‐depth DFT calculations reveal the relationship between the heterojunction and photocatalytic activity and confirm the importance of NiS in accelerating the water dissociation kinetics, which is a crucial factor for photocatalytic HER.

An Efficient, Visible‐Light‐Driven, Hydrogen Evolution Catalyst NiS/ZnxCd1−xS Nanocrystal Derived from a Metal–Organic Framework

Photocatalytic water splitting for hydrogen production using sustainable sunlight is a promising alternative to industrial hydrogen production. However, the scarcity of highly active, recyclable, inexpensive photocatalysts impedes the development of photocatalytic hydrogen evolution reaction (HER) schemes. Herein, a metal-organic framework (MOF)-template strategy was developed to prepare non-noble metal co-catalyst/solid solution heterojunction NiS/Znx Cd1-x S with superior photocatalytic HER activity. By adjusting the doping metal concentration in MOFs, the chemical compositions and band gaps of the heterojunctions can be fine-tuned, and the light absorption capacity and photocatalytic activity were further optimized. NiS/Zn0.5 Cd0.5 S exhibits an optimal HER rate of 16.78 mmol g-1 h-1 and high stability and recyclability under visible-light irradiation (λ>420 nm). Detailed characterizations and in-depth DFT calculations reveal the relationship between the heterojunction and photocatalytic activity and confirm the importance of NiS in accelerating the water dissociation kinetics, which is a crucial factor for photocatalytic HER.

A new sulfur source for the preparation of efficient Cd(1-x)ZnxS photocatalyst for hydrogen evolution reaction

Cd(1-x)ZnxS hexagonal crystals were for the first time synthesized via thermal sulfurization of Cd(1-x)ZnxO particles by using the elemental sulfur as the sulfur source. A temperature profile in the tube furnace was designed to obtain the proposed particle size, crystal structure, and morphology. Synthesized Cd(1-x)ZnxS particles were characterized with scanning electron microscopy (SEM), scanning transmission electron microscopy (STEM), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), Raman spectroscopy, and diffuse reflectance UV–Vis spectroscopy. It was seen that there was a polynomial relationship between the band gap and Cd: Zn ratio in the Cd(1-x)ZnxS. Cd0.58Zn0.23S has shapeless particles between 250 and 500 nm particle size. It was observed that particle size decreased as Zn ratio increased in the Cd(1-x)ZnxS. Cd(1-x)ZnxS hexagonal crystals had nano-step surfaces which were one of the desired factors for achieving high photocatalytic efficiency. Finally, Synthesized Cd(1-x)ZnxS particles were used as photocatalysts for the photocatalytic hydrogen evolution reaction (HER). Cd0.77Zn0.23S structure behaved the most active one among the different compositions of Cd(1-x)ZnxS nanoparticles. Cd0.77Zn0.23S showed almost high photocatalytic activity for HER with 1927 μmol g−1 h−1 hydrogen evolution rate without using noble co-catalyst such as platinum. This good photocatalytic activity was believed to be due to the nanostep surface structure Cd0.77Zn0.23S which led the separation of the reduction and oxidation reaction sites and inhibited the recombination of the generated electrons and holes. Observation of considerably high photocurrent and open circuit potentials and changes in the electrochemical impedance spectroscopy responses supported the photocatalytic activity of the Cd0.77Zn0.23S particles.

Metal-Organic Framework-Derived ZnO/ZnS Heteronanostructures for Efficient Visible-Light-Driven Photocatalytic Hydrogen Production.

Developing highly active, recyclable, and inexpensive photocatalysts for hydrogen evolution reaction (HER) under visible light is significant for the direct conversion of solar energy into chemical fuels for various green energy applications. For such applications, it is very challenging but vitally important for a photocatalyst to simultaneously enhance the visible‐light absorption and suppress photogenerated electron–hole recombination, while also to maintain high stability and recyclability. Herein, a metal–organic framework (MOF)‐templated strategy has been developed to prepare heterostructured nanocatalysts with superior photocatalytic HER activity. Very uniquely, the synthesized photocatalytic materials can be recycled easily after use to restore the initial photocatalytic activity. It is shown that by controlling the calcination temperature and time with MOF‐5 as a host and guest thioacetamide as a sulfur source, the chemical compositions of the formed heterojunctions of ZnO/ZnS can be tuned to further enhance the visible‐light absorption and photocatalytic activity. The nanoscale heterojunction ZnO/ZnS structural feature serves to reduce the average free path of charge carriers and improve the charge separation efficiency, thus leading to significantly enhanced HER activity under visible‐light irradiation (λ > 420 nm) with high stability and recyclability without any cocatalyst.