A distinctive semiconductor-metalloid heterojunction: unique electronic structure and enhanced CO 2 photoreduction activity

Increasing the concentration and separation ability of charge carriers in photocatalysts has still been a crucial issue and challenge to achieve high CO photoreduction performance. Here, we construct a distinctive heterojunction between semiconductor (CeO ) and metalloid (CuS). It has been discovered that, different from conventional semiconductor and Schottky heterojunctions, in this system, electrons (e ) located at the conduction band (CB) of CeO will transfer to the Fermi level in partially occupied band (CB) of CuS and accumulate there. Then, together with transition electrons (e ) excited from the CB below Fermi level or fully filled band (B ) of CuS, these e will further transfer to the lowest unoccupied band (B ) of CuS, finally participate in CO reduction reaction. Because the concentration and separation efficiency of charge carriers has been obviously increased, this heterojunction exhibits remarkably enhanced CO photoreduction performance. In-situ FTIR was conducted to explore the reaction process and the changes of intermediates on the surface of this catalyst during CO 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 CO photoreduction activity.