NiS‐Decorated ZnO/ZnS Nanorod Heterostructures for Enhanced Photocatalytic Hydrogen Production: Insight into the Role of NiS

Abstract

Loading cocatalysts can effectively enhance the surface hydrogen reduction in photocatalytic water splitting by introducing a positive Schottky barrier. NiS is regarded as a promising cocatalyst to replace the noble metals due to its low cost and equivalent or even better performance. However, there is a huge controversy over whether the NiS cocatalyst is used to trap electrons or holes in the photocatalytic process. Herein, a new type of NiS‐decorated ZnO/ZnS (ZnOS) nanorod heterostructure photocatalysts is first designed from the corresponding bimetallic organic frameworks (ZnNi–MOFs). The Zn species in the bimetallic–MOFs can spatially separate the Ni species to restrain their aggregation, which is beneficial for the formation of NiS with a small enough size. The optimal heterostructure photocatalysts exhibit an excellent hydrogen production rate of 27 mmol g−1 h−1, which is about seven times higher than that of the ZnOS heterostructure. X‐ray photoelectron spectroscopy and open‐circuit potential characterizations disclose that NiS can effectively facilitate the migration of the electrons. Density functional theory calculations, including differential charge density, Mulliken population analyses, and d‐band center, intuitively reveal that the real role of NiS in the photocatalytic process is to capture the electrons rather than the holes.

Boosting H2 Production over C60‐Mediated NH2‐MIL‐125(Ti)/Zn0.5Cd0.5S S‐Scheme Heterojunction via Enhanced Interfacial Carrier Separation

“…[46] Figure 5f shows that the H 2 evolution current of NMT decreases with the slowest rate, suggesting the highest H 2 evolution overpotential. [47] In comparison, the overpotential of NMTCZ-45 S-scheme heterojunction is quickly reduced to a certain extent. The lower overpotential could be attributed to the fast transfer of photogenerated electrons and efficiently accelerated electrocatalytic H 2 evolution kinetics, resulting in enhanced PHE activity of NMTCZ-45.…”

An overview of co‐catalysts on metal oxides for photocatalytic water splitting

“…The low‐cost NiS co‐catalyst has received attention because of its comparatively flat Fermi level and large work function (5.50 eV), which is close to that of Pt (5.65 eV) 77 . In a previous study, a ZnO/ZnS/NiS sample exhibited an improved photocatalytic H 2 evolution rate that was approximately 10, 7, and 4 times higher than ZnO, ZnO/ZnS, and Pt/ZnO/ZbS, respectively 78 . Pure NiS has no photocatalytic activity for H 2 production, indicating that NiS acts as the co‐catalyst in NiS/ZnO/ZnS photocatalyst.…”

Noble‐metal‐free MOF Derived ZnS/CeO2 Decorated with CuS Cocatalyst Photocatalyst with Efficient Photocatalytic Hydrogen Production Character

“…The Mott-Schottky (MS) plots of ZnS and CeO 2 showed a positive slope, it indicated that the ZnS and CeO 2 were n-type semiconductor. [50] The flat band potential was derived from the intersection of the tangent line and the x-coordinate of the curve. [51][52] Flat band potentials of ZnS and CeO 2 were 0.3 V and 0.8 V, and they were À 0.06 V and À 0.56 V relative to the standard hydrogen electrode (NHE) band potentials.…”