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.

Photocatalytic production of a C12 liquid biofuel precursor and H2 by Ni(OH)2-ZnIn2S4 in anaerobic water.

Herein, we presented a bifunctional photocatalytic system for 5-hydroxymethylfurfural (HMF) valorization over Ni(OH)2-modified ZnIn2S4. Instead of forming 2,5-diformylfuran C6 products from conventional HMF aerobic oxidation, C-C coupling C12 products and H2 were produced in anaerobic water, which can be an important liquid fuel intermediate and gaseous energy carrier, respectively. This work could spark more insight for biomass utilization.