Ni(OH)₂ surface-modified hierarchical ZnIn₂S₄ nanosheets: dual photocatalytic application and mechanistic insights

The simultaneous utilization of electrons and holes to couple photocatalytic H₂ production with selective biomass transformation has attracted immense interest toward achieving sustainability in the fields of energy and chemical industry. In this study, by assembling highly dispersed Ni(OH)₂ onto ZnIn₂S₄ (ZIS), efficient H₂ evolution along with highly selective photocatalytic oxidation of furfuryl alcohol (FA) to furfural (FF) in pure water was achieved under anaerobic conditions. The H₂ production and FA conversion rates over the optimal Ni-ZIS sample reached about 686 and 583 μmol g^-1 h^-1, respectively, about 4.9 and 1.7 folds as those of pure ZIS. Moreover, the formation of by-products with C-C coupling was dramatically suppressed over Ni-ZIS, resulting in higher selectivity for FF (97%), which is about 2.7-fold that of pure ZIS (36%). Deep mechanistic studies were conducted to reveal the structural evolution and cocatalyst effects of Ni(OH)₂. This study not only offers a feasible paradigm for modifying the surface of catalysts to tune the photoactivity and selectivity for product-oriented alcohol oxidation coupled with efficient H₂ production in water but also reveals the working mechanism of the deposited Ni(OH)₂ over ZIS toward coupling reactions.