Cocatalyst For Photocatalytic H2 Evolution Research Articles

Pd(II), Pt(II) metallosupramolecular complexes as Single-Site Co-Catalyst for photocatalytic H2 evolution

Pd(II), Pt(II) metallosupramolecular complexes as Single-Site Co-Catalyst for photocatalytic H2 evolution

A MOF-derived Bimetallic Co-catalyst for Promoting Visible-light Photocatalytic Hydrogen Evolution on NH2 -MIL-125.

In order to construct noble metal-free co-catalysts to facilitate the transport and separation of photocatalyst carriers, herein, a MOF-based derived bimetallic NiCu0.2 co-catalyst was loaded on NH2 -MIL-125(Ti). The obtained NiCu0.2 /NH2 -MIL-125 exhibited a photocatalytic activity of 161.4 μmol g-1 h-1 for hydrogen evolution, 12.6 times higher than that of the Ni/NH2 -MIL-125 and even slightly better than Pt/NH2 -MIL-125. The work expands the development pathway of cost-effective and highly active bimetallic co-catalysts for photocatalytic H2 evolution.

Partial Sulphidation to Regulate Coordination Structure of Single Nickel Atoms on Graphitic Carbon Nitride for Efficient Solar H2 Evolution.

To develop a non-precious highly efficient cocatalyst to replace Pt on graphitic carbon nitride (g-C3 N4 ) for solar H2 production is great significant, but still remains a huge challenge. The emerging single-atom catalyst presents a promising strategy for developing highly efficient non-precious cocatalyst owing to its unique adjustability of local coordination environment and electronic structure. Herein, this work presents a facile approach to achieve single Ni sites (Ni1 -N2 S) with unique local coordination structure featuring one Ni atom coordinated with two nitrogen atoms and one sulfur atom, confirmed by high-angle annular dark-field scanning transmission electron microscopy, X-ray absorption spectroscopy, and density functional theory calculation. Thanks to the unique electron structure of Ni1 -N2 S sites, the 1095µmol g-1 h-1 of high H2 evolution rate with 4.1% of apparent quantum yield at 420nm are achieved. This work paves a pathway for designing a highly efficient non-precious transition metal cocatalyst for photocatalytic H2 evolution.

Facile Synthesis of Amorphous NiO/Reduced Graphene Oxide as a Cocatalyst for Enhanced Dye-Sensitized Photocatalytic H2 Evolution

It is still a challenge to develop efficient catalysts for hydrogen evolution reaction (HER) via a low-cost and simple method. Herein, we report an amorphous NiO/reduced graphene oxide (A-NG) composite as a cocatalyst for enhanced photocatalytic H2 evolution via dye sensitization. The A-NG composite is facilely fabricated by calcinating the NiCl2/GO precursor at a low temperature of 250 °C. The detailed characterizations show that amorphous NiO presents as tiny nanoparticles highly dispersed on graphene sheets, and nickel carbide is formed at the NiO/graphene interface, which demonstrates the strong interaction between Ni and the defective carbon of graphene. Compared with crystalline NiO/rGO (C-NG), the A-NG cocatalyst shows much enhanced dye-sensitized photocatalytic HER activity because the amorphous NiO nanoparticles can effectively adsorb the dye. As a result, highly dispersed amorphous NiO accelerates the photoinduced electron transfer from the excited dye to the cocatalyst, namely, the amorphous nickel carbide formed between NiO and rGO. This work provides a low-cost and simple method to develop efficient cocatalysts for photocatalytic H2 evolution.

Single-Atom Photocatalysis: Surface-Defect Engineered TiO2 Anatase As a Tunable Platform for Hosting Co-Catalysts Atoms

Single‐atom (SA) or single‐site catalysis (SACs) has over the past years become an increasingly fascinating topic in the catalysis field. SACs have allowed new approaches in heterogeneous catalysis, minimized the use of precious metals, and enabled an unprecedented control over atomistic effects, resulting in improved active sites, and at the same time enabled the design of metal–support interfaces with a high level of structural and chemical control [1,2]. A diverse range of supports and features is known to stabilize isolated metal atoms, notably through pinning at electronic and/or structural defects associated with coordinatively unsaturated sites. However, it is still difficult to create a high density of thermally stable support sites, and hence the fabrication and control of high SA loading remains a challenge [1,2].In this work, an atomic‐scale defect engineering approach to form and control traps for SA sites as co‐catalyst for photocatalytic H2 generation is described. The control over defect types and density can be monitored by electron paramagnetic resonance spectroscopy (EPR) as the most precise method to study atomic scale defects [3]. Thin sputtered TiO2 layers are used as a model photocatalyst, and compared to the more frequently used (001) anatase sheets. To form stable SA co-catalysts, the TiO2 layers are reduced in Ar/H2 under different conditions (leading to different but defined Ti3+‐Ov surface defects), followed by immersion in a dilute solution containing Pt ion in this study. HAADF‐STEM results show that only on the thin‐film substrate can the density of SA sites be successfully controlled by the degree of reduction by annealing. An optimized SA‐Pt decoration can enhance the normalized photocatalytic activity of a TiO2 sputtered sample by a great extent in comparison to a conventional nanoparticle‐decorated TiO2 surface. Most interestingly, in the follow up work based on DFT calculations and experimental data we show that Pd single atom outperforms Pt as the most active co-catalyst for photocatalytic H2 evolution [4]. HAADF‐STEM, XPS, and EPR investigation jointly confirm the atomic nature of the decorated Pt and Pd on TiO2. Importantly, the density of the relevant surface exposed defect centers—thus the density of SA sites, which play the key role in photocatalytic activity—can be precisely optimized.[1] Sh. Mohajernia et al. Adv. Mater. 2020, 32 (16).[2] A. Wang, J. Li, and T. Zhang, Nat. Rev. Chem., 2(6).[3] Sh. Mohajernia et al. J. Mater. Chem. A, 2020, 8(1432)[4] G. Cha et al. iScience, 2021, 8 (24). Figure 1

Covalent organic frameworks with high quantum efficiency in sacrificial photocatalytic hydrogen evolution

Organic semiconductors offer a tunable platform for photocatalysis, yet the more difficult exciton dissociation, compared to that in inorganic semiconductors, lowers their photocatalytic activities. In this work, we report that the charge carrier lifetime is dramatically prolonged by incorporating a suitable donor-acceptor (β-ketene-cyano) pair into a covalent organic framework nanosheet. These nanosheets show an apparent quantum efficiency up to 82.6% at 450 nm using platinum as co-catalyst for photocatalytic H2 evolution. Charge carrier kinetic analysis and femtosecond transient absorption spectroscopy characterizations verify that these modified covalent organic framework nanosheets have intrinsically lower exciton binding energies and longer-lived charge carriers than the corresponding nanosheets without the donor-acceptor unit. This work provides a model for gaining insight into the nature of short-lived active species in polymeric organic photocatalysts.

Phosphorus-enriched platinum diphosphide nanodots as a highly efficient cocatalyst for photocatalytic H2 evolution of CdS

The number of catalytically active sites and their reaction efficiency are two crucial factors for cocatalyst applications in the field of photocatalytic hydrogen (H2) evolution of semiconductor materials. Herein, a novel phosphorus-rich platinum diphosphide (P-rich PtP2) nanodot was developed to efficiently improve the photoactivity of CdS by a facile phytic acid-assisted pyrolysis. The as-synthesized ultrafine PtP2 nanodots (2–5 nm) are evenly distributed on carbon layer (C) and further coupled with CdS to form PtP2@C/CdS photocatalyst via in-situ sulfurization methods. Under visible-light irradiation, the obtained PtP2@C/CdS(10 wt%) photocatalyst presents an optimum H2 evolution rate of 9.76 mmol g−1h−1 with apparent quantum efficiency (AQE) of 41.67% (420 nm), which is 2.2 and 34.8 times higher than that of Pt@C/CdS and blank CdS, respectively. Based on the results of related characterization and density functional theory calculations (DFT), the superior photocatalytic H2-evolution performance of PtP2@C/CdS can be ascribed to the formation of the electron-enriched Pδ− in P-rich PtP2 nanodots, which can serve as the effective H-proton adsorption active site to greatly enhance the photocatalytic activity. This work provides a new perspective into exploiting active site-enriched cocatalyst for the development of high-efficiency photocatalyst.

The Fabrication of Pd Single Atoms/Clusters on COF Layers as Co-catalysts for Photocatalytic H2 Evolution.

The particle size of co-catalysts significantly affects the activity of semiconductors in photocatalysis. Herein, we report that the photocatalytic H2 evolution (PHE) activity of a visible light responsive covalent organic framework (COF) layer supported on SiO2 nanoparticles was greatly promoted from 47.7 to 85.5 μmol/h by decreasing the particle size of the Pd co-catalyst from 3.3 nm to single atoms/clusters. A PHE rate of 156 mmol gCOF-1 h-1 and apparent quantum efficiency up to 7.3% were achieved with the Pd SAs/Cs co-catalyst. The relationship between the activity of Pd in H2 dissociation, proton reduction, and PHE rate suggests that the promotion effect of Pd SAs/Cs is mainly attributed to their enhancement in charge separation of COF layers rather than proton reduction. Furthermore, a photoactive film was fabricated and steady production of H2 was achieved under visible light irradiation and static conditions. The optimization of the particle size of co-catalysts provides an efficient method for enhancing the photocatalytic activity of semiconductors.

Engineering interfacial charge transfer channel for efficient photocatalytic H2 evolution: The interplay of CoPx and Ca2+ dopant

Cobalt phosphide (CoPx) has been developed as a cost-effective cocatalyst for photocatalytic H2 evolution with the advantages of excellent conductivity, strong reduction ability, good thermal and chemical stability. In this work, a facile preparation strategy was proposed to fabricate ultrafine CoPx nanoparticles on the surface of CdS. The effective H2 production over ultrafine CoPx nanoparticles has been realized. In addition, we found Ca2+ as an alkaline earth metal ion can promote the interaction between CdS and CoPx. Both experimental results and density function theory indicate that the Ca2+ dopant can act as surface trapping sites on CdS and lead to efficient separation of photogenerated electron-hole pairs. The integration of CoPx and Ca2+ dopant can synergistically enhance both photogenerated electron-hole separation as well as interfacial charge transfer, which enables a remarkable improvement on the H2 generation performance of CdS. The photocatalytic H2 generation rate of Ca-modified CoPx@CdS can reach up to 2441.5 μmol h−1 under optimal conditions with the apparent quantum efficiency as high as 35.4% at 420 nm. This finding motivates the development of simplified fabrication procedures for constructing and modifying cobalt active sites with efficient photocatalytic H2 generation performance.

As a single atom Pd outperforms Pt as the most active co-catalyst for photocatalytic H2 evolution

SummaryHere, we evaluate three different noble metal co-catalysts (Pd, Pt, and Au) that are present as single atoms (SAs) on the classic benchmark photocatalyst, TiO2. To trap the single atoms on the surface, we introduced controlled surface vacancies (Ti3+-Ov) on anatase TiO2 nanosheets by a thermal reduction treatment. After anchoring identical loadings of single atoms of Pd, Pt, and Au, we measure the photocatalytic H2 generation rate and compare it to the classic nanoparticle co-catalysts on the nanosheets. While nanoparticles yield the well-established the hydrogen evolution reaction activity sequence (Pt > Pd > Au), for the single atom form, Pd radically outperforms Pt and Au. Based on density functional theory (DFT), we ascribe this unusual photocatalytic co-catalyst sequence to the nature of the charge localization on the noble metal SAs embedded in the TiO2 surface.

Noble-metal-free Mo2C co-catalsyt modified perovskite oxide nanosheet photocatalysts with enhanced hydrogen evolution performance

Developing low cost and highly efficient catalysts for photocatalytic hydrogen (H2) evolution reaction holds significant function in water splitting. The co-catalysts load on semiconductor can promote the rapid separation and migration of photon-generated carriers, active interfacial reaction and suppress photocorrosion. Herein, we report the synthesis of Mo2C nanoparticles (NPs) decorated K+Ca2Nb3O10− nanosheets (K+CNO− NSs) heterojunction photocatalyst, where the Mo2C is used as a co-catalyst. The optimal Mo2C/K+CNO− sample with a Mo2C loading amount of 3 wt% yields an enhanced H2 production rate of 686.5 μmol g‒1, which is about 8.8 times higher than that of bare K+CNO‒ NSs (78.1 μmol g‒1). The enhanced photocatalytic activity might be ascribed to the faster photoinduced electrons transfer due to the ultrathin structure of K+CNO− NSs and effective charge carrier separation derived from the abundant contact heterointerfaces between K+CNO− NSs and Mo2C NPs. This study provides a guidance to construct efficient non-noble metal co-catalyst for photocatalytic H2 evolution from water splitting.

(Invited) Self-Activation of TiO2 Nanotubes for Photocatalytic H2 Generation

TiO2 and particularly its anatase form, is one of the most widely studied oxide semiconductors for photocatalytic production of H2 from aqueous solutions.In anatase, the conduction band is situated at an energetic position that allows the transfer of photogenerated electrons to aqueous media and thus the conversion of H+ into H2. Moreover, TiO2 provides an almost unique high resistance against chemical and photocorrosion. On the other hand, photocatalytic H2 production from aqueous electrolytes shows very slow kinetics on all TiO2 surfaces. Therefore, typically decoration of titania with co-catalysts is used to accelerate the H2 evolution kinetics. Most effective co-catalysts are costly noble metals, such as Pt, Pd, or Au. Economically it is of great interest to develop means and approaches to reduce the use of such costly co-catalyst. In the presentation, we discuss efficient noble-metal-free approaches for catalyzing photocatalytic hydrogen generation. A particularly interesting approach is provided by defined defect engineering of anatase. Specific shallow Ti3+ states can promote the generation of photocatalytic H2. Most spectacular is that these catalytic sites can be formed by photoinduced reduction. In other words, under suitable illumination conditions it is possible to create, in situ, energetically suitable Ti3+ states that then act as an intrinsic co-catalyst for photocatalytic H2 evolution. As a result, both co-catalytic formation of active sites and photocatalytic H2 formation is observed. I.e. with increasing illumination time, a light‐induced self‐amplification of the photocatalytic H2 production rate occurs. The effect is characterized by electron paramagnetic resonance (EPR) spectroscopy, reflectivity, and photoelectrochemical techniques. The origin of the self‐activation and amplification behavior observed for anatase nanoparticles and anodically grown self-organized TiO2 nanotube structures will be discussed in the presentation.

Selenium-enriched amorphous NiSe1+x nanoclusters as a highly efficient cocatalyst for photocatalytic H2 evolution

Exploiting and fabricating of novel non-noble metal cocatalysts with abundant active sites is highly required to boost the photocatalytic performance. Herein, selenium-enriched amorphous NiSe1+x nanoclusters (a-NiSe1+x) as a novel cocatalyst were rationally integrated with the TiO2 to greatly boost its hydrogen-generation rate via a simple photoinduced deposition route. It was interesting to find that in comparison with the crystalline nickel selenide (c-NiSe), the a-NiSe1+x evidently displayed more unsaturated active Se atoms because of its highly irregular arrangement structure and small particle size (0.5–2 nm). Photocatalytic results revealed that the a-NiSe1+x nanoclusters could significantly improve the hydrogen-production activity of TiO2 (4095.3 μmol h−1 g−1, AQE = 19.6%), which is higher than that of pristine TiO2 and c-NiSe/TiO2. The outstanding performance of a-NiSe1+x/TiO2 can be attributed to the synergism of facilitated photoelectron transfer from TiO2 to a-NiSe1+x cocatalyst and excellent H2-production active site of Se atoms, which was well revealed by density functional theory (DFT) calculations and in situ irradiated X-ray photoelectron spectroscopy (ISI-XPS) measurement. Based on the above results, an enriched Se-mediated mechanism is raised for the boosted H2-generation rate of a-NiSe1+x/TiO2. Moreover, the present a-NiSe1+x can also be used as the general cocatalyst for typical g-C3N4 and CdS photocatalysts. Considering the gentle preparation, low-cost and admirable activity, the a-NiSe1+x cocatalyst would have tremendousprospects for the fabrication of advanced photocatalytic materials.

Single Cobalt Atom Anchored Black Phosphorous Nanosheets as an Effective Cocatalyst Promotes Photocatalysis

AbstractExploring novel cocatalysts with sufficient active sites and rapid photogenerated carrier separation remains challenge for boosting photocatalytic reactions. Recently, two‐dimensional (2D) black phosphorus (BP) has been developed and recognized to be an ideal platform for anchoring metal ions through lone pair electrons. Herein, we propose a new structure that cobalt atomically dispersed on BP nanosheets (BP−Co), and apply it as cocatalyst for photocatalytic H2 evolution and CO2 reduction under visible light (>420 nm) irradiation. Both scanning transmission electron microscope and X‐ray absorption near edge structure verified the existence of phosphorous‐coordinated Co sites. The interaction between Co and P brings greatly improvement on photocatalytic activities, and 18‐fold enhancement can be achieved on CdS when taking BP−Co as a noble‐metal‐free cocatalyst for H2 evolution, which is higher than that of Pt under the same conditions. Besides, BP−Co can also be used as an effective cocatalyst to promote photocatalytic CO2 reduction in the presence of photosensitizer [Ru(2, 2’‐bipyridy)3]Cl2 with a CO evolution rate of 88.6 μmol h−1, superior to those obtained from the state‐of‐the‐art cocatalysts. It is anticipated that the current work might provide basic understanding as well as new opportunities on 2D BP nanosheets for versatile photocatalytic reactions.

Self-Activation of TiO2 Nanotubes for Photocatalytic H2 Generation

TiO2 and particularly its anatase form, is one of the most widely studied oxide semiconductors for photocatalytic production of H2 from aqueous solutions.In anatase, the conduction band is situated at an energetic position that allows the transfer of photogenerated electrons to aqueous media and thus the conversion of H+ into H2. Moreover, TiO2 provides an almost unique high resistance against chemical and photocorrosion. On the other hand, photocatalytic H2 production from aqueous electrolytes shows very slow kinetics on all TiO2 surfaces. Therefore, typically decoration of titania with co-catalysts is used to accelerate the H2 evolution kinetics. Most effective co-catalysts are costly noble metals, such as Pt, Pd, or Au. Economically it is of great interest to develop means and approaches to reduce the use of such costly co-catalyst. In the presentation, we discuss efficient noble-metal-free approaches for catalyzing photocatalytic hydrogen generation. A particularly interesting approach is provided by defined defect engineering of anatase. Specific shallow Ti3+ states can promote the generation of photocatalytic H2. Most spectacular is that these catalytic sites can be formed by photoinduced reduction. In other words, under suitable illumination conditions it is possible to create, in situ, energetically suitable Ti3+ states that then act as an intrinsic co-catalyst for photocatalytic H2 evolution. As a result, both co-catalytic formation of active sites and photocatalytic H2 formation is observed. I.e., with increasing illumination time, a light‐induced self‐amplification of the photocatalytic H2 production rate occurs. The effect is characterized by electron paramagnetic resonance (EPR) spectroscopy, reflectivity, and photoelectrochemical techniques. The origin of the self‐activation and amplification behavior observed for anatase nanoparticles and nanotubes will be discussed in the presentation.

Ternary Ni2P/reduced graphene oxide/g-C3N4 nanotubes for visible light-driven photocatalytic H2 production

Developing low cost co-catalysts is crucial for both fundamental research and practical application of g-C3N4. In this work, we prepared ternary Ni2P/rGO/g-C3N4 nanotubes with different Ni2P contents for visible-light-driven photocatalytic H2 generation from triethanolamine aqueous solution. The optimal Ni2P/rGO/g-C3N4 produced H2 at a rate of 2921.9 μmol h−1 g−1, which is about 35, 16 and 9 times as large as that of g-C3N4, binary rGO/g-C3N4 and Ni2P/g-C3N4, respectively. The apparent quantum efficiency of optimal Ni2P/rGO/g-C3N4 was 5.6% at λ = 420 nm. We believe that the improved photocatalytic performance of Ni2P/rGO/g-C3N4 originates from the synergistic effect of rGO as electron transfer medium and Ni2P as reaction site, which is supported by photoelectrochemical and photoluminescence measurements. Cyclic experiment demonstrated an excellent stability of Ni2P/rGO/g-C3N4. Moreover, we further studied the effect of other nickel-based compounds by replacing Ni2P with NiS, Ni3C, and Ni3N, respectively. The order of the H2-generation rate is Ni2P/rGO/CNNT > NiS/rGO/CNNT > Ni3C/rGO/CNNT > Ni3N/rGO/CNNT, which could be reasonably explained based on Mott–Schottky plots. Our work reveals that Ni2P can be used as a promising cocatalyst for photocatalytic H2 evolution.

Co-doped Mo-Mo2C cocatalyst for enhanced g-C3N4 photocatalytic H2 evolution

Molybdenum rich molybdenum carbide (Mo-Mo2C) has recently been confirmed as a highly effective non-noble-metal cocatalyst to boost the photocatalytic activity of g-C3N4 for water splitting. However, the activity of Mo-Mo2C is still much lower than that of Pt noble metal based cocatalysts for photocatalytic hydrogen production (PHE). This work reports a highly active cobalt (Co) doped Mo-Mo2C cocatalyst (Co(Mo-Mo2C)) for PHE. The hydrogen production rate of 2.0 wt.% optimal Co(Mo-Mo2C) loaded g-C3N4 (2.0 wt.% Co(Mo-Mo2C)/g-C3N4) photocatalyst can be as high as 11,291 μmol h−1 g−1, at 6.7% apparent quantum efficiency (AQE) at 420 nm, which is 1.4 times greater than that of 2.0 wt.% Pt/g-C3N4 photocatalyst. Catalyst characterizations have pointed out that Co doped Mo-Mo2C cocatalyst is able to efficiently suppress photo-generated charge recombination, thus improving the interfacial charge transfer rate. This research provides novel ideas and technical approaches for designing a noble-metal-free, efficient and environmentally friendly cocatalyst for photocatalytic H2 evolution via water reduction.

Designing CdS-Based Ternary Heterostructures Consisting of Co-Metal and CoOx Cocatalysts for Photocatalytic H2 Evolution under Visible Light.

Heterostructure formation is an effective method used for designing photocatalysts that solve problems caused by photoexcited charge recombination phenomena associated with the photocatalytic water redox reaction. This work reports a new Co-metal-incorporated ternary heterostructured photocatalyst, CdS/CoOx/Co-metal, which enhanced charge separation to increase photocatalytic H2 evolution 30.5-fold in comparison to pure CdS under visible light. This work demonstrates for the first time the effect of the Co metal on photocatalytic H2 evolution using the CdS/CoOx/Co-metal ternary heterostructure. In the ternary heterostructure, Co metal and CoOx act as photogenerated electron- and hole-capturing cocatalysts, respectively. Results from photoelectrochemical studies along with photocatalytic H2 evolution data proved the enhancement of charge transfer and separation in the CdS/CoOx/Co-metal heterostructure due to the addition of Co metal and CoOx. Hence, the synergistic charge separation improvement achieved by the combination of CoOx and the Co metal with CdS produced a photocatalytic H2 evolution rate of 9.54 μmol/h, which is the highest reported H2 evolution rate for a CdS-based system under l sun solar irradiance (>420 nm) to the best of our knowledge.

Light-induced confined growth of amorphous Co doped MoSx nanodots on TiO2 nanoparticles for efficient and stable in situ photocatalytic H2 evolution

Amorphous molybdenum sulfide (a-MoSx) prepared by in situ photoreduction method with an abundance of exposed active sites has been identified as an efficient cocatalyst for catalyzing photocatalytic H2 evolution reaction (HER). However, the intrinsic activity of the a-MoSx cocatalyst toward HER is low due to the unfavorable electronic structures of the active sites. Herein, we report a facile light-induced method for the confined growth of transition metal (TM) doped MoSx (a-TM-MoSx) cocatalysts on TiO2 nanoparticles and their catalytic activity for in situ photocatalytic HER. It is found that doping Co into a-MoSx can greatly enhance the activity of resulted a-Co-MoSx cocatalyst for photocatalytic H2 evolution over TiO2 among the transition metal dopants (Co, Ni, Fe, Cu, Zn) tested. The most efficient a-Co-MoSx cocatalyst (Co/Mo = 1/4 and 4 mol% loading) loaded TiO2 (TiO2/a-Co-MoSx) shows a H2 evolution rate of 133.8 μmol h−1, which is 3.3 times higher than that of a-MoSx loaded TiO2 (TiO2/a-MoSx). Moreover, the TiO2/a-Co-MoSx photocatalyst shows excellent recycling H2 evolution stability. The characterization results reveal that a-Co-MoSx cocatalyst can not only effectively capture the photogenerated electrons of TiO2 to greatly enhance the separation efficiency of photogenerated charges but also significantly reduce the overpotential of HER due to the formation of highly active “CoMoS” sites, thus synergistically enhancing the catalytic activity of TiO2/a-Co-MoSx. Moreover, the light-induced growth of a-Co-MoSx on TiO2 is found to readily couple with the in situ photocatalytic HER. Therefore, this work provides a simple and efficient strategy for designing high-performance a-MoSx-based cocatalysts for stable in situ photocatalytic H2 evolution.

Bimetallic PtNi/g-C3N4 nanotubes with enhanced photocatalytic activity for H2 evolution under visible light irradiation

Bimetallic PtNi-decorated graphitic carbon nitride (g-C3N4) nanotubes were prepared through calcining the mixture of urea and thiourea in the presence of Pluronic F127, followed by deposition of bimetallic PtNi nanoparticles (NPs) via chemical reduction. It is found that the photocatalytic activity of PtNi/g-C3N4 nanotubes is strongly dependent on the molar ratio of Pt/Ni and the highest activity is observed for Pt1Ni1/g-C3N4. Under visible light (λ > 420 nm) irradiation, the H2 generation rate over Pt1Ni1/g-C3N4 nanotubes is 104.7 μmol h−1 from a triethanolamine (10 vol%) aqueous solution, which is higher than that of Pt/g-C3N4 nanotubes (98.6 μmol h−1) and is about 47.6 times higher than that of pure g-C3N4 nanotubes. The cyclic photocatalytic reaction indicates that our Pt1Ni1/g-C3N4 nanotubes function as a stable photocatalyst for visible light-driven H2 production. The effect of bimetallic PtNi NPs in the transfer and separation of photogenerated charge carriers occurring in the excited g-C3N4 nanotubes was investigated by performing photo-electrochemical and photoluminescence measurements. Our results reveal that bimetallic PtNi could replace Pt as a promising cocatalyst for photocatalytic H2 evolution with better performance and lower cost.