Fabrication of layered Fe2P-Cd0.5Zn0.5S nanoparticles with a reverse heterojunction for enhanced photocatalytic hydrogen evolution

Incorporating Ni-Polyoxometalate into the S-Scheme Heterojunction to Accelerate Charge Separation and Resist Photocorrosion for Promoting Photocatalytic Activity and Stability

The emerging polyoxometalate (POM) nanomaterials are transition metal oxygen anion clusters with d⁰ electronic configurations, which could be attractive and potential photocatalysts. Hence, a nickel (Ni)-substituted polyoxometalate K₆Na₄[Ni₄(H₂O)₂(PW₉O₃₄)₂]·32H₂O (Ni₄POM)-incorporating step (S)-scheme heterojunction was developed to promote photocatalytic activity and stability in H₂ and H₂O₂ production. The multielectron transfer through variable valence metal centers in Ni₄POM would facilitate the recombination of invalid charges through the S-scheme pathway. Moreover, incorporating Ni₄POM into the S-scheme heterojunction can broaden the light absorption range and meanwhile lead to resistance to photocorrosion to promote the optical and chemical stability of Cd_0.5Zn_0.5S (CZS). The optimized CZSNi-70 exhibited a H₂ evolution rate of 42.32 mmol g^-1 h^-1 under visible-light irradiation with an apparent quantum yield of 32.27% at 420 nm and a H₂O₂ production rate of 295.4 μmol L^-1 h^-1 under 420 nm light-emitting diode irradiation. This work can provide a new view for the development of transition metal-substituted POM-based stable and efficient S-scheme photocatalysts.

The highly improved hydrogen evolution performance of a 0D/0D MoP-modified P-doped Mn0.5Cd0.5S photocatalyst

In this paper, we present a MoP/P-Mn_0.5Cd_0.5S photocatalytic material (PMOMCS-Px). A novel catalyst can efficiently split water into hydrogen without precious metals. In the sacrificial agent environment, the HER (hydrogen evolution rate) of PMOMCS-P5 was 4368.25 μmol g^-1 h^-1 which was 11.4 times greater than the HER of Mn_0.5Cd_0.5S (383.19 μmol g^-1 h^-1), and its hydrogen production performance was better than that of Pt/Mn_0.5Cd_0.5S (2.0 wt% Pt). Furthermore, the hydrogen evolution performance of PMOMCS-P5 under pure water conditions was also examined, and the HER of PMOMCS-P5 was 209.76 μmol g^-1 h^-1, which was 20.4 times that of Mn_0.5Cd_0.5S (10.29 μmol g^-1 h^-1). Its characterization proved that the introduction of the co-catalyst MoP and P doping inhibited the recombination of e^- and h⁺, enhanced the reduction capacity, and reduced the hydrogen precipitation reaction overpotential of PMOMCS-Px, thus enhancing the hydrogen production performance of PMOMCS-Px. Therefore, an efficient and economical photocatalyst was prepared.

Nickel phosphonate-derived Ni2P@N-doped carbon co-catalyst with built-in electron-bridge for boosting the photocatalytic hydrogen evolution

To construct photocatalytic systems that can efficiently convert solar energy to hydrogen energy, numerous studies have been focused on transition metal phosphides (TMPs) co-catalysts, which display low overpotential and cost...

One-step preparation of cobalt phosphate at room temperature for effective photocatalytic H2 evolution

Cobalt phosphate materials were prepared in the present work in one step at room temperature using different raw materials and characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and N₂ gas adsorption. Cobalt phosphates exhibit 3D flower-like structures, and the assembly of nanosheets (petals of the "flowers") of cobalt phosphate prepared with sodium phosphate and cobalt acetate as raw materials (denoted as Co-P(A)) is more incompact than that of cobalt phosphate prepared with diammonium hydrogen phosphate and cobalt nitrate as raw materials (denoted as Co-P(B)) due to the former's mildly basic environment. The cobalt phosphates show relatively high photocatalytic activity for H₂ evolution reaction (HER) in the presence of Eosin Y as a sensitizer in an aqueous triethanolamine solution. The activity of Co-P(A) (0.40 mmol h^-1 g^-1) exceeds that of Co-P(B) (0.19 mmol h^-1 g^-1), which can be attributed to a more dispersive nanosheet and larger BET-specific surface area of Co-P(A). The mechanisms of photocatalytic HER and the formation of flower-like Co₃(PO₄)₂ were discussed. The present system comprising of only abundant elements contributes toward the development of cost-efficient solar HER to achieve sustainable development.

Nickel hydroxide as a non-noble metal co-catalyst decorated on Cd0.5Zn0.5S solid solution for enhanced hydrogen evolution

The study of non-noble metal photocatalysts provides practical significance for hydrogen evolution applications. Herein, new Cd_0.5Zn_0.5S/Ni(OH)₂ catalysts were fabricated through simple hydrothermal and precipitation methods. The photocatalytic performance of the Cd_0.5Zn_0.5S/Ni(OH)₂ composites under visible light was significantly improved, which was attributed to the wider visible light absorption range and less recombination of electron–hole pairs. The composite with a Ni(OH)₂ content of 10% showed the best hydrogen evolution rate of 46.6 mmol g⁻¹ h⁻¹, which was almost 9 times higher than that of pristine Cd_0.5Zn_0.5S. The severe photo-corrosion of Cd_0.5Zn_0.5S was greatly improved, and the Cd_0.5Zn_0.5S/Ni(OH)₂ composite exhibited a very high hydrogen evolution rate after three repeated tests. The excellent photocatalytic performance was due to the non-noble metal Ni(OH)₂ co-catalyst. The excited electrons were transferred to the co-catalyst, which reduced electron–hole recombination. Moreover, the co-catalyst offered more sites for photocatalytic reactions. This study researched the mechanism of a co-catalyst composite, providing new possibilities for non-noble metal photocatalysts.

This study researched the mechanism of a co-catalyst composite, providing new possibilities for non-noble metal photocatalysts.

Controlling the coordination environment of Co atoms derived from Co/ZIF-8 for boosting photocatalytic H2 evolution of CdS

Regulating the coordination environment of metal-N_x species by replacing N with low electronegativity atoms is an approach of tuning the electrocatalytic performance of metal-based sites. However, such effects on the enhancement of photocatalytic H₂ evolution over semiconductors are not discussed yet. Herein, we designed and prepared Co-based cocatalysts with controlled coordination environment via calcination Co/ZIF-8 loaded with triphenylphosphine followed by a sulfurization treatment. It was then used as cocatalyst to modify CdS. The effects of the coordination environment of Co atoms on the H₂ evolution activity of CdS were discussed. The obtained Co was co-stabilized by N, P, and S atoms and embedded in graphitic carbon (denoted as Co-N_xPS/C). Experimental results indicated that the Co-N_xPS/C exhibited high activity in enhancing H₂ evolution of CdS with a value of 1260 μmol after 5 h irradiation. The simultaneous replacement of N with P and S atoms in N-stabilized Co embedded in carbon could enhance light harvesting, accelerate the transfer of photogenerated electrons from CdS to carbon with increased electrons accumulation ability and conductivity, improve charge separation efficiency, and enhance proton reduction kinetics. It is believed that the results of this study could promote the development of other high performance MOF-derived atomically dispersed cocatalysts to increase photocatalytic H₂ evolution.