Cobalt incorporation-induced photocatalytic reactivity enhancement in ZnIn2S4 nanosheets for effective hydrogen production

Heteroatom incorporation is commonly used resorts to construct highly active centers in photocatalysis. Especially, cobalt with tunable spin orbitals is a desirable dopant for photocatalytic hydrogen production. However, the charge and adsorption properties associated with cobalt-incorporated sites have not been elucidated. In this work, the cobalt with the spin state (e4t23) was successfully incorporated into ZnIn2S4 nanosheets. Experimental and calculated results show that the cobalt-induced electron occupancy displays an obvious interaction with oxygen-containing intermediates, which promotes water dissociation. Meanwhile, the enhanced covalency of CoS bonds effectively balances the hydrogen adsorption/desorption ability, which is favorable for H2 production. Nevertheless, the weakened water adsorption restricts the improvement of H2 production as the amount of Co doping increases. Under the balance of these factors, optimum doping of cobalt in ZnIn2S4 is achieved and it shows a significantly enhanced H2-evolution rate of 72.1 μmol h−1, which is 5.5 times higher than that of ZnIn2S4.