A distinctive semiconductor-metalloid heterojunction: unique electronic structure and enhanced CO₂ photoreduction...

Increasing the concentration and separation ability of charge carriers in photocatalysts has still been a crucial issue and challenge to achieve high CO₂ photoreduction performance. Here, we construct a distinctive heterojunction between semiconductor (CeO₂) and metalloid (CuS). It has been discovered that, different from conventional semiconductor and Schottky heterojunctions, in this system, electrons (e_sc^-) located at the conduction band (CB) of CeO₂ will transfer to the Fermi level in partially occupied band (CB) of CuS and accumulate there. Then, together with transition electrons (e_tr^-) excited from the CB below Fermi level or fully filled band (B_-1) of CuS, these e_sc^- will further transfer to the lowest unoccupied band (B₁) of CuS, finally participate in CO₂ reduction reaction. Because the concentration and separation efficiency of charge carriers has been obviously increased, this heterojunction exhibits remarkably enhanced CO₂ photoreduction performance. In-situ FTIR was conducted to explore the reaction process and the changes of intermediates on the surface of this catalyst during CO₂ photoreduction. Given that this type of heterojunction can only be established between a semiconductor and a metalloid and exhibits special electron transfer behavior, this work really provides an unconventional strategy for the design of photocatalysts with superior CO₂ photoreduction activity.