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Tungsten phosphide (WP) as an excellent hydrogen evolution reactions (HER) catalyst has attracted widespread attention, but its HER activity is low in alkaline media due to high water dissociation barrier. Herein, noble-metal-free cocatalyst WP/WO 3 composite was synthesized by adjusting the P/W molar ratio in the raw material using a simple solid phosphidation reaction. The structure, morphology, composition, and optoelectronic properties of the as-synthesized samples were characterized by XRD, SEM, TEM, XPS, UV–vis DRS, PL techniques, and electrochemical methods. Under visible light irradiation (λ ≥ 420 nm), the photocatalytic HER activities of the as-prepared samples using Eosin-Y (EY) dye as a sensitizer and trimethylamine (TMA) as an electron donor were investigated. The result shows that WP/WO 3 composite as a cocatalyst exhibits excellent photocatalytic HER activity and good stability. The highest apparent quantum yield (AQY) reaches 32.8 %. The presence of amorphous WO 3 in crystalline WP can improve the separation efficiency of photogenerated electrons and holes, reduce HER overpotential, and promote the dissociation of H 2 O in alkaline media. Therefore, the photocatalytic HER activity of WP/WO 3 composite is higher than that of single crystalline WP. [Display omitted] • WP/WO 3 composite was prepared by adjusting the P/W molar ratio in the raw material. • WP/WO 3 composite exhibits high dye-sensitized photocatalytic HER activity. • WO 3 coupling with WP promotes the separation of photocarriers and H 2 O dissociation. • The AQY of 32.8 % at 420 nm is achieved under the optimized conditions. [ABSTRACT FROM AUTHOR]

Using non-toxic red phosphorus as the phosphorus source, Ni 2 P was synthesized and in situ loaded on Cd 0.5 Zn 0.5 S photocatalyst by a simple solvothermal method for photocatalytic H 2 evolution under visible light (λ ≥ 420 nm) irradiation. The as-prepared samples were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and high-resolution transmission electron microscopy (HRTEM), ultraviolet–visible diffuse reflectance spectra (UV–Vis DRS), Brunauer–Emmett–Teller (BET) surface area measurements and electrochemistry techniques. The photocatalytic hydrogen evolution activity over Cd 0.5 Zn 0.5 S is significantly increased by in situ-loaded Ni 2 P due to the intimate interface contact and efficient charge transfer from Cd 0.5 Zn 0.5 S to Ni 2 P. The 4 wt%Ni 2 P-loaded Cd 0.5 Zn 0.5 S photocatalyst shows five times higher H 2 evolution rate than that of the pristine Cd 0.5 Zn 0.5 S. The highest H 2 evolution rate of 65.6 μmol/h and the apparent quantum yield (AQY) of 29% at 420 nm is achieved under the optimized conditions. The noble metal free Ni 2 P is stable during 20 h photocatalytic reaction. [ABSTRACT FROM AUTHOR]

A series of ZIS-x [ZIS and x represent the ZnIn 2 S 4 and the addition amount of TEOA (mmol) in the synthesis process, respectively] were synthesized via a hydrothermal method using triethanolamine (TEOA) as a template. The as-synthesized photocatalysts were characterized by X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDX), scanning electron microscopy (SEM), Ultraviolet-visible (UV–vis) diffuse reflection spectroscopy and Brunauer–Emmett–Teller (BET) surface area measurement. The effects of TEOA on the crystal structures, morphologies and optical properties of ZIS-x products were investigated. The photocatalytic activity was tested in the reaction of H 2 evolution from aqueous TEOA solution under visible light irradiation (λ ≥ 420 nm). It was found that the activity of ZIS-x synthesized in TEOA solution was higher than that of ZIS-0 synthesized in pure water. This can be attributed to the facts that ZIS-x is composed of single ZnIn 2 S 4 and more TEOA can be adsorbed on ZIS-x surface, which improves the separation of an electron-hole pair. When TEOA was used as an electron donor, it can enhance notably photocatalytic H 2 evolution with its simultaneous degradation. The effect of TEOA concentration on the H 2 evolution rate is consistent with a Langmuir–Hinshelwood kinetic model. The optimal amount of Pt loaded on the photocatalyst is 0.50 wt%, and the optimal pH for photocatalytic H 2 evolution is 13. On the optimal condition, the rate of hydrogen evolution over ZIS-2.0 is 2 times as high as that of ZIS-0 during 20 h irradiation. [ABSTRACT FROM AUTHOR]

[Display omitted] • CoP/g-C 3 N 4 hybrid photocatalyst was prepared in which CoP acts as a noble-metal-free HER cocatalyst. • CoP/g-C 3 N 4 composite exhibits high dye-sensitized photocatalytic HER activity and stability. • Photogenerated electrons can effectively transfer among EY, g-C 3 N 4 and CoP. • The AQY of 56.3% at 420 nm is achieved under the optimized conditions. In this paper, CoP/g-C 3 N 4 composite photocatalysts were prepared, in which CoP was used as a noble-metal-free cocatalyst. Using dye Eosin Y (EY) as the sensitizer and triethanolamine (TMA) as the electron donor, the performance of the photocatalytic H 2 evolution reaction (HER) under visible light (λ ≥ 420 nm) was investigated. When the loading of CoP is 5 wt%, the CoP(5 wt%)/g-C 3 N 4 composite shows the best photocatalytic HER performance, even better than that of Pt(5 wt%)/g-C 3 N 4. The apparent quantum yield (AQY) achieves 56.3% under 420 nm light irradiation, one of the best values reported for noble-metal-free cocatalysts in the dye-sensitized HER system, and the catalyst also exhibits good stability under 36 h of irradiation. The high activity and stability of CoP(5 wt%)/g-C 3 N 4 are the results of efficient electron transfer among photoexcited EY, g-C 3 N 4 and CoP, and the excellent HER activity of CoP. [ABSTRACT FROM AUTHOR]

Graphitic carbon nitride (g-C3N4), as an attractive metal-free polymer photocatalyst, has attracted extensive attention in energy and environmental fields in recent years. The photoactivity of bulk g-C3N4 is moderate on account of solid-phase thermal-condensation synthesis. This leads to inadequate light absorption, limited surface area, and easy recombination of charge carriers. The composition and nanostructure of g-C3N4 have been studied extensively. Molten-salt modulation is fascinating because of its "green" credentials and the properties of liquid-phase reaction systems. The review focuses mainly on molten-salt modulation of the composition and structure of g-C3N4 based-photocatalysts. We focus on elemental doping, molecular doping, and defect engineering, as well as control of the crystal structure, multi-dimensional structure, hom/heterostructures for photocatalytic applications. This review provides new insights to develop g-C3N4-based photocatalysts with control of composition and structure by facile molten-salt modulation in energy-conversion and environmental fields. [ABSTRACT FROM AUTHOR]

[Display omitted] • Ni 12 P 5 was in situ anchored on ZnIn 2 S 4 via a solvothermal route. • The intimate interface between Ni 12 P 5 and ZnIn 2 S 4 can promote the charge transfer from ZnIn 2 S 4 to Ni 12 P 5. • ZnIn 2 S 4 loaded with 6 wt% Ni 12 P 5 exhibits the best hydrogen production activity and excellent stability. • The possible photocatalytic mechanism was discussed. It is a great challenge to develop efficient, stable and inexpensive hydrogen evolution reaction (HER) catalysts for photocatalytic water-splitting. In this paper, Ni 12 P 5 (NP) was in situ anchored on the surface of ZnIn 2 S 4 (ZIS) via a solvothermal route with nickel chloride and red phosphorus as ingredients. Using triethanolamine as sacrificial agent, the photocatalytic hydrogen evolution activity of NP/ZIS was studied under visible light irradiation. At the same time, the composition, structure, morphology and photoelectrochemical properties of the as-obtained samples were analyzed through a sequence of characterization techniques. ZIS loaded with 6 wt% NP (6NP/ZIS) exhibits the best hydrogen evolution activity and excellent stability. The H 2 evolution rate of 6NP/ZIS is 5.4 times higher than that of pristine ZIS and well beyond that of the physical mixture (6NP + ZIS) or even that of the optimal Pt/ZIS under the same conditions. The maximal apparent quantum yield (AQY) of 22.7 % at 400 nm is achieved, superior to the most reported performance of ZnIn 2 S 4 -based photocatalysts for HER. The anchor of NP can not only enhance the visible light absorption intensity, but also reduce the HER overpotential. More importantly, the intimate interface between ZIS and NP can promote the separation and migration of photo-excited carriers, thereby enhancing the activity of photocatalytic hydrogen evolution. The possible photocatalytic reaction mechanism was discussed. [ABSTRACT FROM AUTHOR]

Searching for non-noble-metal cocatalyst for hydrogen evolution in photocatalytic water–splitting has attracted much attention. Herein, molybdenum phosphide (MoP) as an efficient and stable cocatalyst was prepared in a facile phosphorization process at relatively low temperatures under N 2 atmosphere, and the effect of preparation temperature (300–500 °C) was studied. Using Eosin Y (EY) and the prepared sample as catalyst (sensitizer) and cocatalyst, respectively, the photocatalytic activity for hydrogen evolution was investigated in aqueous trimethylamine (TMA) solution under visible light irradiation (λ ≥ 420 nm). MoP prepared at 400 °C (MoP-400) exhibits the highest sensitization activity and superior stability, and the maximal apparent quantum yield (AQY) for hydrogen evolution is up to 48.0% at 420 nm, much higher than the most reported data for MoP-based photocatalysts. The highest activity can be attributed to the highest P content in MoP-400 and the rapidest electron transfer between photoexcited EY and MoP-400. The possible mechanism was discussed. [Display omitted] • Molybdenum phosphide (MoP) as a cocatalyst for EY-sensitized photocatalytic HER. • The effect of preparation temperature of MoP was studied. • MoP-400 exhibits the highest sensitization activity and superior stability. • The possible mechanism for EY-sensitized photocatalytic HER was proposed. [ABSTRACT FROM AUTHOR]

The construction of a composite photocatalyst with two suitable semiconductors is an effective strategy to improve the transport and separation of the photoexcited carrier pairs. Herein, it is the first time to report the new concept of anisotropic heterojunctions (H and J type) in layered ZnIn 2 S 4 nanosheets as an example. Due to the anisotropic conductivity, the resistance of the electron transfer along ZnIn 2 S 4 layers to a second semiconductor (J type heterojunction), is much less than that across the layers (H type heterojunction). As a result, the J type heterojunction can achieve higher photocatalytic activity than H type one. Furthermore, ZnIn 2 S 4 /In(OH) 3 heterojunction with the J type structure was successfully fabricated by a simple approach, namely, In(OH) 3 was selectively assembled at the rims of ZnIn 2 S 4 nanosheets via hydrothermal transformation of the precursor precipitate with its mother solution obtained by adding Na 2 S into the solution of stoichiometric In 3+ and excessive Zn 2+ . The intimate-contact J type heterojunction with in-situ photodeposited Pt shows efficient photocatalytic H 2 evolution under visible irradiation, leading to a high apparent quantum yield of 38.3% at 420 nm with a low optimal Pt loading of 0.25 wt%. This work provides a new insight for the development of efficient heterojunction photocatalysts with layered semiconductors. [ABSTRACT FROM AUTHOR]

[Display omitted] • The triazine and heptazine units is directional modulated by a green approach. • Small content of SPP in-situ booss the formation of heptazine based CN. • Excess content of SPP tends to form triazine based CN. • The triazine and heptazine based SPP-MS-CN shows superior photocatalytic activity. Hollow SPP-MS-CN nanotubes have been developed through a green one-step approach by sodium polyphosphate (SPP) in-situ mediated molten salt (MS) thermal condensation of melamine for the first time. In which, the structure of SPP-MS-CN with triazine and heptazine units can been directionally modulated by the SPP content. The molten salts at high-temperature function as green solvents to facilitate mass transfer, which tends to form triazine based CN. Addition of SPP mediates the fluidity of molten salt system, which in-situ modulates the thermal condensation process, boosting the formation of the extended π-conjugated system of heptazine based CN. The 0.5 wt% SPP-MS-CN exhibit photocatalytic H 2 evolution rate up to 1785 µmol h−1 g−1, which is 2.16 times higher than that of molten salt synthesis of carbon nitride (MS-CN), even 14.5 times enhancement of photocatalytic H 2 evolution rate over pure CN obtained by directly thermal condensation of melamine. It reveals that the hollow structures endow SPP-MS-CN with increased specific surface area, and the formed heptazine structure of SPP-MS-CN benefit for charge carrier separation and transfer and H 2 reduction ability, which favors for the remarkable photocatalytic activity. Our work opens a new window for in-situ modulation of the structure of CN photocatalysts. [ABSTRACT FROM AUTHOR]