Valence state effect of Cu on photocatalytic CO_(2)reduction

Copper(Cu)is extensively employed in photocatalytic CO_(2)reduction reactions for the production of high-value products.The valence state of transition metals plays a pivotal role in influencing the catalytic process.However,due to the complex valence state changes of Cu in the CO_(2)reduction reaction,research on its valence state effect is lacking.The current work is to prepare a series of TiO_(2)/CuX with stable Cu valence composition using different copper halides(CuX and CuX_(2),X=Br or Cl)as precursors.The results show that the CuBr_(2)loading leads to Cu^(+)/Cu^(2+) mixed cocatalyst and exhibits the highest activity for CO_(2)photoreduction.The CH4 evolution rate of the TiO_(2)/CuBr_(2)catalyst is as high as 100.59μmol h^(-1)g^(-1),which is 6.6 times that of pristine TiO_(2).The CH4 selectivity reaches 77%.The enhanced catalytic activity and selectivity can be ascribed to the efficient surface adsorption,activation,excellent carrier separation,and transfer ofCu^(+)/Cu^(2+) mixed cocatalyst.Our findings provide a reference for designing highly active Cu-based photocatalysts.