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

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 (esc-) 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 (etr-) excited from the CB below Fermi level or fully filled band (B-1) of CuS, these esc- 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.