Cocatalyst For Photocatalytic Hydrogen Evolution Research Articles

Noble-metal-free Ni(dmgH)2/CdS nanocomposite for enhanced photocatalytic H2 generation

In this study, we report an economic and noble-metal-free photosynthetic system of Ni(dmgH)2/CdS composites (dmgH = dimethylglyoxime). This system, consisting of CdS as a photocatalyst and Ni(dmgH)2 as a co-catalyst, exhibits enhanced photoresponse, accelerated charge transfer, facilitating the separation of electrons and holes, and efficient hydrogen evolution under visible light. It was found that the catalytic efficiency of CdS was significantly influenced by the loading amount of Ni(dmgH)2. An optimum activity was achieved at 10 wt% Ni(dmgH)2, resulting a stable hydrogen generation rate of 32.744 mmol h−1 g−1. This rate is nearly 98 times higher than that of bare CdS under similar conditions, indicating that Ni(dmgH)2 can be a highly efficient noble-metal-free co-catalyst for photocatalytic hydrogen evolution with CdS. The mechanism for the hydrogen evolution of the Ni(dmgH)2/CdS composites was also proposed. This study demonstrates that the combination CdS semiconductor with small proportion of transition-metal-based co-catalyst may provide a reliable platform for a stable, earth-abundant, and low-cost system for solar-to-hydrogen conversion, paving the way for promising advancements in green energy research.

Structurally disordered MoSe2 with rich 1T phase as a universal platform for enhanced photocatalytic hydrogen production

The improvement of surface reactivity in noble-metal-free cocatalysts is crucial for the development of efficient and cost-effective photocatalytic systems. However, the influence of crystallinity on catalytic efficacy has received limited attention. Herein, we report the utilization of structurally disordered MoSe2 with abundant 1T phase as a versatile cocatalyst for photocatalytic hydrogen evolution. Using MoSe2/carbon nitride (CN) hybrids as a case study, it is demonstrated that amorphous MoSe2 significantly enhances the hydrogen evolution rate of CN, achieving up to 11.37 μmol h−1, surpassing both low crystallinity (8.24 μmol h−1) and high crystallinity MoSe2 (3.86 μmol h−1). Experimental analysis indicates that the disordered structure of amorphous MoSe2, characterized by coordination-unsaturated surface sites and a rich 1T phase with abundant active sites at the basal plane, predominantly facilitates the conversion of surface-bound protons to hydrogen. Conversely, the heightened charge transfer capacity of the highly crystalline counterpart plays a minor role in enhancing practical catalytic performance. This approach is applicable for enhancing the photocatalytic hydrogen evolution performance of various semiconducting photocatalysts, including CdS, TiO2, and ZnIn2S4, thereby offering novel insights into the advancement of high-performance non-precious catalysts through phase engineering.

Tailoring hydrophilicity and electronic interactions and transfer: Enhancing hydrogen production through size-tuned CuNi alloys

Investigating eco-friendly, effective, and economical cocatalysts for photocatalytic hydrogen evolution remains a significant challenge. In this research, different methods were utilized to synthesize CuNi nanoalloys of varied particle sizes supported on Al-doped SrTiO3 (Al-STO), delving into the effects of CuNi alloy particle size, catalyst material hydrophilicity, and charge dynamics on photocatalytic efficiency. The study meticulously examined how different particle sizes of CuNi alloys impacted the photocatalytic activity of Al-STO, noting that larger CuNi alloy nanoparticles significantly enhance and stabilize photocatalytic hydrogen evolution, achieving a rate of 58.14 µmol/h. A detailed comparative analysis was also conducted, focusing on the nanoalloys' distribution, elemental composition, and optical characteristics, thereby elucidating the critical role of particle size in influencing the physicochemical properties of CuNi nanoalloys. Furthermore, comprehensive Density Functional Theory (DFT) calculations were carried out to confirm the robust interactions between the alloy and support, as well as the electronic synergies within the CuNi alloy components. These interactions are shown to greatly affect charge transfer efficiency and the adsorption energy of the reactants, such as water molecules. This investigation paves the way for adopting non-precious bimetallic cocatalysts in efficient photocatalytic hydrogen production, offering valuable insights for future clean energy research endeavors.

Frontispiece: Engineering a Self‐Grown TiO2/Ti‐MOF Heterojunction with Selectively Anchored High‐Density Pt Single‐Atomic Cocatalysts for Efficient Visible‐Light‐Driven Hydrogen Evolution

Photocatalysis. The synthesis of a Z-scheme heterojunction TiO2/Ti-MOF-Pt with selectively anchored high-density Pt single-atomic cocatalysts for photocatalytic hydrogen evolution is reported by Chunshan Song, Xiang Wang, Xinwen Guo et al. in their Research Article (e202217439).

Covalent Grafting of A Nickel Thiolate Catalyst onto Covalent Organic Frameworks for Boosted Photocatalytic Activity.

Covalent organic frameworks (COFs) have recently emerged as prospective photoactive materials with noble Pt cocatalyst for the photocatalytic hydrogen evolution. In this work, a series of SH-group-functionalized covalent organic frameworks, TpPa-1-SH-X, were prepared by reaction of p-phenylenediamine (Pa) and 1,3,5-triformylphloroglucinol (Tp), with p-NH2C6H4SH as a modulating agent. The reaction of TpPa-1-SH-X with Ni(II) acetylacetonate Ni(acac)2 gave nickel thiolate-immobilized TpPa-1 (TpPa-1-SNi-X). The highest hydrogen evolution rate was 10.87 mmol h-1 g-1, which was an enhancement of 16.47, 3.83, and 1.84 times than that of the parent TpPa-1, covalent-bond-free [(p-NH2C6H4S)2Ni]n/TpPa-1-SH-10, and 3 wt% Pt-deposited TpPa-1, respectively. This enhanced photocatalytic hydrogen evolution is ascribed to enhanced crystallinity, the use of Ni(II) thiolate as a cocatalyst and covalent bonding between the cocatalyst and TpPa-1.

Inside Cover: A Deprotection‐free Method for High‐yield Synthesis of Graphdiyne Powder with In Situ Formed CuO Nanoparticles (Angew. Chem. Int. Ed. 43/2022)

A deprotection-free method was developed for the synthesis of graphdiyne (GDY) powder with in-situ formed CuO nanoparticles, as reported by Mohamed Nawfal Ghazzal, Li-Zhu Wu et al. in their Research Article (e202210242). The prepared CuO/GDY was demonstrated to be an excellent co-catalyst for photocatalytic hydrogen evolution, comparable to the state-of-art Pt cocatalyst. The work will widen the use of GDY and facilitate its scaling up to industrial level.

Amorphous sulfur-rich CoSx nanodots as highly efficient cocatalyst to promote photocatalytic hydrogen evolution over TiO2

In this work, amorphous cobalt sulfide with a sulfur-rich structure (sr-CoSx) is developed as the cocatalyst for photocatalytic hydrogen evolution. Through a facile hydrothermal reaction, sr-CoSx nanodots are in situ grown on TiO2 to obtain a heterojunction photocatalyst (sr-CoSx/TiO2). The as-prepared photocatalyst exhibits remarkable improved hydrogen evolution performance compared with TiO2. Under the irradiation of xenon lamp, the hydrogen evolution rate of sr-CoSx/TiO2 can reach 507 μmol h−1 g−1, which is about 121 times that of pristine TiO2, indicating that sr-CoSx is a highly efficient cocatalyst to promote hydrogen evolution on TiO2. Moreover, sr-CoSx/TiO2 exhibits better performance than crystalline CoS2 or amorphous CoS modified TiO2, suggesting the important role of sulfur-rich structure and amorphous state in promoting the cocatalytic effect. Electrochemical and photoluminescence measurements show the most efficient carrier separation between sr-CoSx and TiO2, which also contributes to its high photocatalytic hydrogen evolution performance.

A Deprotection-free Method for High-yield Synthesis of Graphdiyne Powder with In Situ Formed CuO Nanoparticles.

With a direct band gap, superior charge carrier mobility, and uniformly distributed pores, graphdiyne (GDY) has stimulated tremendous interest from the scientific community. However, its broad application is greatly limited by the complicated multistep synthesis process including complex deprotection of hexakis-[(trimethylsilyl)ethynyl]benzene (HEB-TMS) and peeling of GDY from the substrates. Here, we describe a deprotection-free strategy to prepare GDY powder by directly using HEB-TMS as the monomer. When CuCl was used as the catalysts in DMF solvent, the yield of GDY powder reached ≈100 %. More interestingly, uniformly dispersed CuO nanoparticles with an average diameter of ≈2.9 nm were in situ formed on GDY after the reaction. The prepared CuO/GDY was demonstrated an excellent co-catalyst for photocatalytic hydrogen evolution, comparable to the state-of-art Pt co-catalyst. The deprotection-free approach will widen the use of GDY and facilitate its scaling up to industrial level.

Single site Co-S anchored on carbon nitride as a highly active cocatalyst for photocatalytic hydrogen evolution

The low utilization rate of photo-generated carriers in graphite-phase carbon nitride (g-C3N4) is the main factor limiting its photocatalytic performance. In this work, to begin with single-atom Co was inserted into the structure of g-C3N4, then it was vulcanized to prepare composite Co-S single-site in g-C3N4. The results show that the Co-S single-site cocatalyst was successfully synthesized and was stably anchored in the structure of g-C3N4. As an active site, it can not only enhance the reaction activity, but also capture electrons to provide transfer channels for the photo-generated carrier, thereby enhancing the photocatalytic hydrogen evolution performance of g-C3N4. The hydrogen production of Co-S single-site modified g-C3N4 reaches 72.85 μmol (per 0.02 g photocatalyst) under visible light, which is 9 times higher than that of pure g-C3N4. This work provides a reasonable method for the preparation of composite single-site cocatalyst.

Surface Anchoring and Active Sites of [Mo3S13]2- Clusters as Co-Catalysts for Photocatalytic Hydrogen Evolution.

Achieving light-driven splitting of water with high efficiency remains a challenging task on the way to solar fuel exploration. In this work, to combine the advantages of heterogeneous and homogeneous photosystems, we covalently anchor noble-metal- and carbon-free thiomolybdate [Mo3S13]2– clusters onto photoactive metal oxide supports to act as molecular co-catalysts for photocatalytic water splitting. We demonstrate that strong and surface-limited binding of the [Mo3S13]2– to the oxide surfaces takes place. The attachment involves the loss of the majority of the terminal S22– groups, upon which Mo–O–Ti bonds with the hydroxylated TiO2 surface are established. The heterogenized [Mo3S13]2– clusters are active and stable co-catalysts for the light-driven hydrogen evolution reaction (HER) with performance close to the level of the benchmark Pt. Optimal HER rates are achieved for 2 wt % cluster loadings, which we relate to the accessibility of the TiO2 surface required for efficient hole scavenging. We further elucidate the active HER sites by applying thermal post-treatments in air and N2. Our data demonstrate the importance of the trinuclear core of the [Mo3S13]2– cluster and suggest bridging S22– and vacant coordination sites at the Mo centers as likely HER active sites. This work provides a prime example for the successful heterogenization of an inorganic molecular cluster as a co-catalyst for light-driven HER and gives the incentive to explore other thio(oxo)metalates.

High-yield exfoliation of MoS2 (WS2) monolayers towards efficient photocatalytic hydrogen evolution

Monolayer MoS2 (WS2) nanosheets have triggered tremendous interest due to their fascinating unique properties, but high-yield production of single-layer MoS2 (WS2) still remains an enormous challenge and of great interest. Herein, we report a facile efficient partial etching strategy to tailor thickness and lateral size of MoS2 (WS2) so as to increase the fraction of edges, which remarkably enhanced the yield of monolayer MoS2 (20%) and WS2 (12%) nanosheets by liquid phase exfoliation. As a proof of concept, the exfoliated monolayer MoS2 (WS2) nanosheets were applied as the cocatalysts for photocatalytic hydrogen evolution. Notably, the optimized hybrids exhibit excellent hydrogen evolution performance, which are over 31-fold (MoS2/CdS) and 47-fold (WS2/CdS) higher that of bare CdS counterpart, respectively. Hence, this work not only may pave the new way for the high-yield production of transition-metal dichalcogenides monolayers by liquid phase exfoliation, but also provide the possibility for the further efficiently exfoliating other two-dimension layered materials.

One-pot synthesis of yolk-shell Cu/Cu2O nanospheres with tunable morphologies for assisting photocatalytic hydrogen evolution

We report a facile, one-pot synthesis of spherical Cu/Cu 2 O yolk-shell nanocrystals (Cu/Cu 2 O YSNSs) with tunable morphologies and explored their applications for assisting photocatalytic hydrogen evolution. The success of current synthesis relies on the reduction of Cu(NO 3 ) 2 by ascorbic acid in the presence of octadecyl trimethylammonium chloride (OTAC) and hexamethylenetetramine (HMTA). It is found that the variation of OTAC concentration would lead to the formation of Cu/Cu 2 O YSNSs with tunable morphologies. The as-prepared Cu/Cu 2 O YSNSs are further anchored by TiO 2 nanoparticles (Degussa P25) to construct Cu/Cu 2 O/TiO 2 nanocomposites for applications in photocatalytic H 2 evolution under simulated sunlight irritation. The resulting metal-semiconductor nanostructures have remarkable photocatalytic activity in H 2 evolution from water-methanol mixtures, with the product rate being almost 97 times greater than that of the pure P25 catalysts. Such improvement should be attributed to the unique hollow structure and the presence of multi-valent copperish species. The current study describes a feasible one-pot strategy to synthesize copperish oxide nanocrystals with tunable yolk-shell morphologies and validates their promising use in as co-catalyst for photocatalytic hydrogen evolution to illustrate the advantage from both the structure and composition. Yolk-shell Cu/Cu 2 O nanospheres with tunable morphologies are prepared in high purity via a one-pot method. By anchoring with TiO 2 nanoparticles (P25), they exhibit excellent photocatalytic activity (~97 times greater than P25 in hydrogen production rate) and long-term durability towards photocatalytic hydrogen evolution, illustrating the structural and morphological advantages.

Recent research progress of bimetallic phosphides-based nanomaterials as cocatalyst for photocatalytic hydrogen evolution

Hydrogen energy (H2) has been considered as the most possible consummate candidates for replacing the traditional fossil fuels because of its higher combustion heat value and lower environmental pollution. Photocatalytic hydrogen evolution (PHE) from water splitting based on semiconductors is a promising technology towards converting solar energy into sustainable H2 fuel evolution. Developing high-activity and abundant source semiconductor materials is particularly important to realize highly efficient hydrogen evolution as for photocatalysis technology. However, unmodified pristine photocatalysts are often unable to overcome the weakness of low performance due to their limitations. In recent years, transition metal phosphides (TMPs) were used as valid co-catalysts to replace the classic precious metal materials in the process of photocatalytic reaction owing to their lower cost and higher combustion heat value. What is more, bimetallic phosphides have been also caused widespread concern in H2 evolution reaction owing to its much lower overpotential, more superior conductivity, and weaker charge carriers transfer impedance in comparison to those of single metal phosphides. In this minireview, we concluded the latest developments of bimetallic phosphides for a series of photocatalytic reactions. Firstly, we briefly summarize the present loading methods of bimetallic phosphides (BMPs) anchored on the photocatalyst. After that, the H2 evolution efficiency based on BMPs as cocatalyst is also studied in detail. Besides, the application of BMPs-based host photocatalyst for H2 evolution under dye sensitization effect has also been discussed. At last, the current development prospects and prospective challenges in many ways of BMPs are proposed. We sincerely hope this minireview has certain reference value for great developments of BMPs in the future research.

Phosphorylation of NiAl-layered double hydroxide nanosheets as a novel cocatalyst for photocatalytic hydrogen evolution

In previous studies, it has been shown that phosphorus and phosphate can improve the conductivity, change the electronic structure, and accept electrons from catalysts. In this study, we obtained phosphorylated NiAl-layered double hydroxide (P-LDH) nanosheets and used them as a novel cocatalyst in photocatalytic hydrogen evolution. After assembly with g-C3N4 via an in situ process, these noble-metal-free composite photocatalysts showed superior photocatalytic hydrogen evolution activity. It was also found that the efficiency of H2 production on the optimal composite was 1.5 times that of Pt-modified g-C3N4. Characterization of the photocatalysts revealed that the effects of P-LDH were different from those of other bimetallic LDHs, showing a lower overpotential and faster reaction kinetics of H2 evolution. Moreover, it was found that P-LDH has a higher surface work function than that of g-C3N4, leading to the formation of an interfacial electric field from CN toward P-LDH. Therefore, modifying P-LDH can efficiently improve the interfacial charge transfer rate, suppress photogenerated charge recombination, and lower the surface overpotential of g-C3N4. This study serves as guidance on the design of more effective cocatalysts for photocatalytic hydrogen evolution reactions.

Boosting photocatalytic hydrogen evolution using a noble-metal-free co-catalyst: CuNi@C with oxygen-containing functional groups

Oxygen functional groups are often overlooked in most carbon coated co-catalyst for photocatalytic hydrogen evolution, and its influences on proton reduction are not been well considered. In this work, a noble-metal-free co-catalyst CuNi alloy nanoparticle wrapped in a carbon layer containing oxygen-containing functional groups (CuNi@CO) was designed and synthesized. Under visible light irradiation, the photocatalytic H2 evolution rate of CuNi@CO/g-C3N4 was 2.36 mmol g−1 h−1, which was higher than that of Pt co-catalyst at the same conditions. Density functional theory calculations and mechanistic studies indicate that the H adsorption free energy on the CuNi@CO was more suitable for hydrogen evolution than that of Pt, where the CO groups on the carbon layer surface modulated the work function of CuNi alloy. It is believed that the understanding the function of surface CO group can broaden the research directions of photocatalyst modification and improve the activity of photocatalytic hydrogen evolution.

Dual-phase metal nitrides as highly efficient co-catalysts for photocatalytic hydrogen evolution

Low solar-to-fuel conversion in conventional semiconductor-based photocatalysts limits their commercial applications. Searching for highly efficient cost-effective co-catalysts is desirable for the development of artificial photosynthesis systems. In this work, we report a simple yet efficient electrostatic self-assembly process to synthesize one-dimensional Co4N-WNx-CdS composites for visible light-driven hydrogen evolution in pure water. Biphasic transition metal nitrides Co4N-WNx with high conductivity and enriched active sites leads to multi-level electrons transfer and lower over-potential for hydrogen production. Co4N-WNx-CdS composite, with optimized wt%, exhibits the highest rate of photocatalytic hydrogen evolution (14.42 mmol g−1h−1) under vacuum condition. This rate is ~ 8 times higher than that of the Pt-CdS composite (1.78 mmol g−1h−1).

Correction: Elucidating the formation and active state of Cu co-catalysts for photocatalytic hydrogen evolution

Correction for ‘Elucidating the formation and active state of Cu co-catalysts for photocatalytic hydrogen evolution’ by Jasmin S. Schubert et al., J. Mater. Chem. A, 2021, DOI: 10.1039/d1ta05561e.

Elucidating the formation and active state of Cu co-catalysts for photocatalytic hydrogen evolution.

The design of active and selective co-catalysts constitutes one of the major challenges in developing heterogeneous photocatalysts for energy conversion applications. This work provides a comprehensive insight into thermally induced bottom-up generation and transformation of a series of promising Cu-based co-catalysts. We demonstrate that the volcano-type HER profile as a function of calcination temperature is independent of the type of the Cu precursor but is affected by changes in oxidation state and location of the copper species. Supported by DFT modeling, our data suggest that low temperature (<200 °C) treatments facilitate electronic communication between the Cu species and TiO2, which allows for a more efficient charge utilization and maximum HER rates. In contrast, higher temperatures (>200 °C) do not affect the Cu oxidation state, but induce a gradual, temperature-dependent surface-to-bulk diffusion of Cu, which results in interstitial, tetra-coordinated Cu+ species. The disappearance of Cu from the surface and the introduction of new defect states is associated with a drop in HER performance. This work examines electronic and structural effects that are in control of the photocatalytic activity and can be transferred to other systems for further advancing photocatalysis.

Integrating Ru-modulated CoP nanosheets binary co-catalyst with 2D g-C3N4 nanosheets for enhanced photocatalytic hydrogen evolution activity

Developing high-efficient and low-cost photocatalysts is of great significance yet challenging for photocatalytic hydrogen evolution. Herein, we report a 2D/2D Ru-modulated CoP nanosheets (Ru-CoP-x, where x refers the Ru-to-Co molar ratio)/g-C3N4 nanosheets (GCN NSs) ternary hybrid as a photocatalyst for hydrogen evolution under visible light. The optimal photocatalyst 25% Ru-CoP-1:8/GCN NSs exhibits an excellent hydrogen evolution rate of 1172.5 µmol g−1 h−1 under visible light with a high apparent quantum efficiency (AQE) of 3.49% at 420 nm, which is close to Pt/g-C3N4 photocatalytic system and higher than most reported transition metal phosphides (TMP)/g-C3N4 photocatalytic system. Experimental results indicate that the higher photocatalytic hydrogen evolution performance can be mainly attributed to the binary Ru-CoP-x co-catalyst with efficient charge separation and promoted surface water reduction kinetics, and the 2D/2D self-assembly structure with strong interface Schottky effect and short charge transport distance. This study provides a new approach to develop cost-effective Pt-alternative co-catalysts for photocatalytic hydrogen evolution by incorporating a small amount of ruthenium into the transition metal phosphides.

Construction of the Ni2P/MoP Heterostructure as a High-Performance Cocatalyst for Visible-Light-Driven Hydrogen Production

Transition metal phosphides are regarded as promising cocatalysts for photocatalytic hydrogen evolution, although there are still many limitations, such as a relatively lower electrical conductivit...