Cocatalyst For Photocatalytic Hydrogen Production Research Articles

Cobalt phosphide nanowires as efficient co-catalyst for photocatalytic hydrogen evolution over Zn0.5Cd0.5S

Previous studies have shown that co-catalysts play a pivotal role for improving both the activity and reliability of semiconductors in photocatalytic hydrogen production, however, designing highly efficient and cost-effective co-catalysts to replace expensive and rare metals is still a big challenge. In this work, DFT (density functional theory) is utilized to guide the application of CoP NWs (nanowires) as an earth-abundant co-catalyst for photocatalytic hydrogen production. Metallic 1D CoP NWs is rationally integrated with Zn0.5Cd0.5S solid solution semiconductor for the first time, to induce a remarkably improved photocatalytic hydrogen production activity of 12,175.8 μmol h−1 g−1, which is 22 times higher than that of the pristine Zn0.5Cd0.5S. This outstanding activity benefits from the collaborative advantages of excellent metallic conductivity and the rigid 1D nanostructure of CoP NWs. Moreover, the mechanism investigations demonstrate that this excellent activity arises from the strong electronic coupling, favourable band structure, highly efficient charge separation and migration based on the powerful characterizations, such as time-resolved PL decay spectra and photoelectrochemical methodology. This work brings new opportunities to employ 1D co-catalysts on photocatalysts for improving the catalytic activities in hydrogen production from water.

One-Step Synthesis of Nb2 O5 /C/Nb2 C (MXene) Composites and Their Use as Photocatalysts for Hydrogen Evolution.

Hydrogen production through facile photocatalytic water splitting is regarded as a promising strategy to solve global energy problems. Transition-metal carbides (MXenes) have recently drawn attention as potential co-catalyst candidates for photocatalysts. Here, we report niobium pentoxide/carbon/niobium carbide (MXene) hybrid materials (Nb2 O5 /C/Nb2 C) as photocatalysts for hydrogen evolution from water splitting. The Nb2 O5 /C/Nb2 C composites were synthesized by one-step CO2 oxidation of Nb2 CTx . Nb2 O5 grew homogeneously on Nb2 C after mild oxidation, during which some amorphous carbon was also formed. With an optimized oxidation time of 1.0 h, Nb2 O5 /C/Nb2 C showed the highest hydrogen generation rate (7.81 μmol h-1 gcat-1 ), a value that was four times higher than that of pure Nb2 O5 . The enhanced performance of Nb2 O5 /C/Nb2 C was attributed to intimate contact between Nb2 O5 and conductive Nb2 C and the separation of photogenerated charge carriers at the Nb2 O5 /Nb2 C interface; the results presented herein show that transition-metal carbide are promising co-catalysts for photocatalytic hydrogen production.

Effective and Durable Co Single Atomic Cocatalysts for Photocatalytic Hydrogen Production.

This research reports for the first time that single cobalt atoms anchored in nitrogen-doped graphene (Co-NG) can serve as a highly effective and durable cocatalyst for visible light photocatalytic hydrogen production from water. Results show that, under identical conditions, the hydrogen production rate (1382 μmol/h) for 0.25 wt % Co-NG-loaded CdS photocatalyst (0.25 wt % Co-NG/CdS) is 3.42 times greater than that of nitrogen-doped graphene (NG) loaded CdS photocatalyst (NG/CdS) and about 1.3 times greater than the greatest hydrogen production rate (1077 μmol/h) for 1.5 wt % Pt nanoparticle loaded CdS photocatalyst (1.5 wt % Pt-NPs/CdS). At 420 nm irradiation, the quantum efficiency of the 0.25 wt % Co-NG/CdS photocatalyst is 50.5%, the highest efficiency among those literature-reported non-noble metal cocatalysts. The Co-NG/CdS nanocomposite-based photocatalyst also has an extended durability. No activity decline was detected during three cyclic photocatalytic life span tests. The very low cocatalyst loading, along with the facile preparation technology for this non-noble metal cocatalyst, will significantly reduce the hydrogen production costs and finally lead to the commercialization of the solar catalytic hydrogen production process. Based on experimental results, we conclude that Co-NG can successfully replace noble metal cocatalysts as a highly effective and durable cocatalyst for renewable solar hydrogen production. This finding will point to a new way for the development of highly effective, long life span, non-noble metal-based cocatalysts for renewable and cost-effective hydrogen production.

In situ photodeposition of MoSx on CdS nanorods as a highly efficient cocatalyst for photocatalytic hydrogen production

In situ photodeposition of MoSx on CdS-nanorods for photocatalytic HER was achieved with (NH4)2MoS4 as a precursor. The optimal MoSx loading amount is 0.2 wt% and its performance is comparable to the well-known Pt cocatalyst. A junction in form of Cd–S–Mo bond was proposed to account for the higher HER activity.

High efficiency and stable tungsten phosphide cocatalysts for photocatalytic hydrogen production

Low-cost and abundant tungsten phosphide (WP) is observed as an active cocatalyst for photocatalytic H2 production from water.

Comparative activity of CdS nanofibers superficially modified by Au, Cu, and Ni nanoparticles as co-catalysts for photocatalytic hydrogen production under visible light

Comparative activity of CdS nanofibers superficially modified by Au, Cu, and Ni nanoparticles as co-catalysts for photocatalytic hydrogen production under visible light

Nickel-based cocatalysts for photocatalytic hydrogen production

Photocatalytic water splitting for hydrogen (H2) generation using semiconductor materials is considered as one of the promising avenues for direct solar-to-fuel conversion. In this context, cocatalysts play very significant roles in improving the efficiency of semiconductor-based photocatalytic process. Considering potential future applications, cocatalysts based on cheap and earth-abundant materials are of importance for cost-effective solar-to-hydrogen conversion. This review is devoted to recent progresses in developing Ni-based cocatalysts for semiconductor-based photocatalytic H2 production. Different kinds of Ni-based materials, including inorganic metal and compounds, hydrogenases, as well as molecular complexes, that can function as cocatalysts in combination with semiconductors for photocatalytic H2 generation are discussed in detail. The structural features and functional mechanisms of various semiconductor-cocatalyst composite systems are reviewed. Finally, a brief discussion on future directions, challenges and opportunities in this fascinating area of research is also provided.

Ultra-thin Cu2S nanosheets: effective cocatalysts for photocatalytic hydrogen production.

Herein, we achieved successful synthesis of 2D Cu2S nanosheets (NS) with a thickness of 1.2 nm by a novel strategy. The key to obtain ultra-thin Cu2S NS was the use of a unique sulfur precursor which not only supplied sulfur in a controlled manner, but also directed the formation of a 2D structure. The as-prepared Cu2S NS were proved to be effective cocatalysts for photocatalytic hydrogen production. The H2 production rate of Cu2S NS/TiO2 reached 1430.4 μmol g(-1) h(-1), which was 4.9 times higher than that of TiO2.

Cobalt phosphide as a highly active non-precious metal cocatalyst for photocatalytic hydrogen production under visible light irradiation

Co2P nanoparticles were applied to photocatalytic hydrogen evolution in aqueous acidic media, and simultaneously, dl-mandelic acid was transformed into benzoylformic acid.

Enhanced photocatalytic H2-production activity of bicomponent NiO/TiO2 composite nanofibers

Hydrogen has been regarded as an ideal candidate for the replacement of conventional fossil fuels due to its environmental friendliness and recycling possibility. In this work, mesoporous NiO/TiO2 bicomponent composite nanofibers were prepared by a electrospinning and calcination method. The H2-production activity of the prepared samples was examined by water splitting using methanol as scavenger under simulated solar Xenon lamp irradiation. The effect of NiO loading on the microstructure and photocatalytic H2-production activity of NiO/TiO2 composite samples was studied and discussed. The results demonstrated that the presence of a small amount of NiO obviously inhibited the growth of TiO2 crystallites. With increasing the NiO content, the average crystallite size further decreased. In contrast, the Brunauer–Emmett–Teller (BET) specific surface areas, pore volumes and average pore size steadily increased. Photocatalytic H2-production experiment confirmed that NiO was an efficient co-catalyst for the photocatalytic H2 production of TiO2. The optimal NiO loading was determined to be 0.25wt.%, giving a H2-production rate of 337μmolh−1g−1 with apparent quantum efficiency (QE) of 1.7%, which exceeded the rate on pure TiO2 by more than 7 times. The enhanced H2-production activity was due to the deposition of NiO clusters on the surface of TiO2, which suppressed the recombination of photogenerated electron–hole pairs, reduced the overpotential of hydrogen production and catalyzed production of hydrogen. This work showed that low-cost and earth-abundant NiO could be used as co-catalyst for photocatalytic hydrogen production.

Noble-Metal-Free Ni(OH)2-Modified CdS/Reduced Graphene Oxide Nanocomposite with Enhanced Photocatalytic Activity for Hydrogen Production under Visible Light Irradiation

A series of nickel hydroxide-modified cadmium sulfide/reduced graphene oxide (Ni(OH)2-CdS/rGO) nanocomposites were synthesized and characterized. The photocatalytic activity of the as-prepared Ni(OH)2-CdS/rGO materials for hydrogen production from water under visible light irradiation (λ > 420 nm) was investigated. The results demonstrated that Ni(OH)2 is an efficient cocatalyst for photocatalytic hydrogen production and rGO can significantly enhance the rate of photocatalysis. The optimal Ni(OH)2 loading was found to be 1.0 wt %, giving a rate for hydrogen production of 4731 μmol·h–1·g–1, which is nearly 10 times higher than that of CdS/rGO photocatalyst under the same condition. This work demonstrated the synergetic effect of Ni(OH)2 and rGO to enhance catalytic activity for visible light-driven hydrogen production.

Enhanced photocatalytic H2-production activity of CdxZn1−xS nanocrystals by surface loading MS (M = Ni, Co, Cu) species

To investigate the role of metal sulfides as co-catalyst for photocatalytic hydrogen production under visible light irradiation, we have loaded small amounts of transition-metal sulfides (MS), such as NiS, CoS and CuS, onto the surface of CdxZn1−xS solid solution. It can be found that the rate of H2 evolution over the MS/Cd0.4Zn0.6S was 5 times higher than that of the pure Cd0.4Zn0.6S, and is comparable to the Cd0.4Zn0.6S modified with 1wt% platinum (Pt) co-catalysts. The MS/Cd0.4Zn0.6S photocatalysts were characterized by X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), UV–visible spectrophotometer (UV–vis), and photoluminescence (PL) spectroscopy. It can be speculated that the MS provided active sites for H2 production and caused the migration of excited electrons from Cd0.4Zn0.6S toward MS, leading to the enhancement of photocatalytic activity.

Role of platinum-like tungsten carbide as cocatalyst of CdS photocatalyst for hydrogen production under visible light irradiation

Abstract To investigate the role of platinum-like tungsten carbide as a cocatalyst for photocatalytic hydrogen production under visible light irradiation, we fabricated for the first time a composite material consisting of WC and CdS by a precipitation/hydrothermal method. The composite prepared by this procedure consisted of well-dispersed WC and CdS, as confirmed by TEM mapping analysis. The WC/CdS composite photocatalyst exhibited a high rate of hydrogen production, comparable to that of Pt/CdS, under visible light irradiation ( λ ≥ 420 nm) from water containing sulfide and sulfite ions as hole scavengers. Like Pt cocatalyst loaded on the surface of CdS, WC provides active sites for proton reduction and causes fast diffusion of photoelectrons generated from CdS toward WC, leading to high photocatalytic activity of hydrogen production.