Integrating electronic structure regulation and dynamic active sites construction on NixCd1-xS-Ni0 photocatalyst for efficient hydrogen evolution

Abstract

Regulating electronic structure and enriching active sites of photocatalysts are effective strategies to promote hydrogen evolution. Herein, a unique Ni_xCd_1-xS-Ni⁰ photocatalyst, including the surface nickel (Ni) doping and atomic Ni⁰ anchoring sites, is successfully prepared by Ni²⁺ ions exchange reaction (Ni²⁺+ CdS → Ni_xCd_1-xS) and in-situ photo-induction of Ni⁰(Ni²⁺+Ni_xCd_1-xS→hνNi_xCd_1-xS-Ni⁰), respectively. As to Ni doping, the Ni replaced cadmium (Cd) atoms introduce hybridized states around the Fermi level, modulating the electronic structure of adjacent S atoms and optimizing the photocatalytic activity of sulfur (S) atoms. Besides, photogenerated Ni⁰ atoms, anchored on unsaturated S atoms, act as charge transfer bridges to reduce Ni²⁺ ions in the solution to Ni clusters (Ni_xCd_1-xS-Ni⁰→ne^-Ni_xCd_1-xS-Ni). Subsequently, the displacement reaction of Ni clusters with protons (H⁺) spontaneously proceeds to produce hydrogen (H₂) in an acidic solution (Ni_xCd_1-xS-Ni→2H⁺H₂↑+Ni²⁺+Ni_xCd_1-xS-Ni⁰). The equilibrium of photo-deposition/dissolution of Ni clusters realizes the construction of dynamic active sites, providing sustainable reaction centers and enhancing surface redox kinetics. The Ni_xCd_1-xS-Ni⁰ exhibits a high hydrogen evolution rate of 428 mmol·h^-1·g^-1 with a quantum efficiency of 75.6 % at 420 nm. This work provides the optimal S electronic structure for photocatalytic H₂ evolution and constructs dynamic Ni clusters for chemical replacement reaction. This work provides the optimal S electronic structure for photocatalytic H₂ evolution and constructs dynamic Ni clusters for displacement reaction, opening a dual pathway for efficient water reduction.

Keywords: Displacement reaction; Dynamic active sites; Electronic structure modulation; Hydrogen evolution; Photocatalysis.