Synergy of Dopants and Defects in Porous ZnIn₂S₄ Nanoflakes for Enhanced Photocatalytic HydrogenEvolution

Designing and fabricating photocatalysts with abundant intrinsic active sites and a fast carrier separation capability remains a great challenge for efficient photocatalytic hydrogen evolution reactions (PHERs). In this paper, cobalt (Co) cations are incorporated into two-dimensional (2D) porous ZnIn₂S₄ nanoflakes by a controllable cation-exchange-mediated strategy, and self-adapting S vacancies (Vs) are rationally constructed to stimulate catalytic activity on the inert basal plane. The surface state of ZnIn₂S₄ nanoflakes is regulated by the Vs structure and doped Co atoms through a surface modification strategy to achieve an efficient PHER. Theoretical calculations and experimental results show that by introducing Co dopants into ZnIn₂S₄, Co preferentially replaces Zn atoms and induces the generation of abundant Vs, thus optimizing the adsorption energy of the reaction intermediate (H*) and enhancing the PHER dynamics. The Co dopants and Vs show dominant synergistic effects in modulating the regional charge separation and activating the inert basal plane. More importantly, the optimal PHER rate of Co-ZnIn₂S₄ reaches 1.20 mmol g^–1 h^–1, which is 5.2 times higher than that of the pristine ZnIn₂S₄ nanoflakes. In addition, this robust 2D porous configuration guarantees the stability of the catalytic reaction. The present work gives an expandable direction for enhancing the photocatalytic activity of the basal plane on transition metal sulfides.