Atomic Ni directional-substitution on ZnIn2S4 nanosheet to achieve the equilibrium of elevated redox capacity and efficient carrier-kinetics performance in photocatalysis

It is a challenge to coordinate carrier-kinetics performance and the redox capacity of photogenerated charges synchronously at the atomic level for boosting photocatalytic activity. Herein, the atomic Ni was introduced into the lattice of hexagonal ZnIn₂S₄ nanosheets (Ni/ZnIn₂S₄) via directional-substituting Zn atom with the facile hydrothermal method. The electronic structure calculations indicate that the introduction of Ni atom effectively extracts more electrons and acts as active site for subsequent reduction reaction. Besides the optimized light absorption range, the elevation of E_f and E_CB endows Ni/ZnIn₂S₄ photocatalyst with the increased electron concentration and the enhanced reduction ability for surface reaction. Moreover, ultrafast transient absorption spectroscopy, as well as a series of electrochemical tests, demonstrates that Ni/ZnIn₂S₄ possesses 2.15 times longer lifetime of the excited charge carriers and an order of magnitude increase for carrier mobility and separation efficiency compared with pristine ZnIn₂S₄. These efficient kinetics performances of charge carriers and enhanced redox capacity synergistically boost photocatalytic activity, in which a 3-times higher conversion efficiency of nitrobenzene reduction was achieved upon Ni/ZnIn₂S₄. Our study not only provides in-depth insights into the effect of atomic directional-substitution on the kinetic behavior of photogenerated charges, but also opens an avenue to the synchronous optimization of redox capacity and carrier-kinetics performance for efficient solar energy conversion.