Zn0.5Cd0.5S photocatalysts with loaded Cu2+ and Ni2+ dual active sites for promoted syngas production†

Abstract

The Zn0.5Cd0.5S semiconductor is widely recognized as a promising photocatalyst due to its strong light absorption capability and high conduction band potential, enabling the conversion of CO2 and H2O into syngas (CO and H2). However, its catalytic efficiency is significantly limited by the lack of active sites, restricting the simultaneous evolution of CO and H2. In this study, Cu2+ and Ni2+ are co-introduced into Zn0.5Cd0.5S nanoparticles as active sites to selectively promote the evolution of CO and H2, respectively, thereby synergistically enhancing the photocatalytic activity for overall syngas production. The Zn0.5Cd0.5S photocatalysts incorporating Cu2+ and Ni2+ dual active sites were synthesized via a simple precipitation method. Experimental results demonstrate that Cu2+ active sites significantly enhance CO yield, whereas Ni2+ active sites improve H₂ production. Theoretical calculations reveal that Cu2+ and Ni2+ play distinct roles in the reaction mechanisms: Cu2+ acts as the active site for CO₂ reduction, markedly reducing the Gibbs free energy barrier for intermediate adsorption, while Ni2+ serves as the active site for hydrogen evolution in water splitting, facilitating H* adsorption. The synergistic effect of Ni2+ and Ni2+ significantly enhances the photocatalytic performance of Zn0.5Cd0.5S in syngas production. This study provides a facile strategy for active site modulation to tailor photocatalytic behaviour, offering insights into the rational design and synthesis of highly efficient photocatalysts for syngas production.