Engineering d-band states of (CuGa) Zn1-2Ga2S4 material for photocatalytic syngas production

The d-band states of catalytic materials participate in adsorbing reactive intermediate species and determine the catalytic behaviors in CO2 reduction reactions. However, surface d-band states relating to the photocatalytic CO2 reduction reactions behaviors are rarely concerned. Herein, a slightly amount of Cd2+ is decorated on the surface of (CuGa)xZn1-2xGa2S4 material (Cd2+/(CuGa)xZn1-2xGa2S4) to tune the surface d-band states for improved CO2 reduction reactions. The Cd2+/(CuGa)xZn1-2xGa2S4 is fabricated via the facile ions-exchange method to make that slightly Zn2+ is substituted by Cd2+. The Cd2+/(CuGa)xZn1-2xGa2S4 exhibits much enhanced photocatalytic activity in CO2 reduction reactions to produce CO and water splitting to produce H2. Physical characterizations show that the energy band structure is not changed obviously. Density functional theory reveals that Cd2+/(CuGa)xZn1-2xGa2S4 possesses a closer shift of d-band center to Fermi level than (CuGa)xZn1-2xGa2S4, suggesting easier adsorption of CO2 reduction reactive intermediates after Cd2+ decoration. Further calculations confirm that a relatively reduced adsorption Gibbs energy of reactive intermediates in CO2 reduction reaction is required on Zn atoms in Cd2+/(CuGa)xZn1-2xGa2S4 material, benefiting the photocatalytic CO2 reduction reactions. This work engineers surface d-band states by surface Cd2+ decoration, which gives an effective strategy to design highly efficient photocatalysts for syngas production.