Built-in electric field intensified by photothermoelectric effect drives charge separation over Z-scheme 3D/2D In2Se3/PCN heterojunction for high-efficiency photocatalytic CO2 reduction

It is a challenging issue to further drive charge separation through the oriented design of Z-scheme heterojunction in the exploitation of cost-effective photocatalytic materials. In this contribution, the unique Z-scheme 3D/2D In2Se3/PCN heterojunction is developed through implanting In2Se3 microspheres on PCN nanosheets using an in situ growth technique, which acquires the effective CO generation activity from photocatalytic CO2 reduction (CO2R). The CO yield of 4 h in the CO2R reaction over the optimal In2Se3/PCN-15 sample reaches up to 11.40 and 2.41 times higher than that of individual PCN and In2Se3, respectively. Such greatly enhanced photocatalytic performance is primarily the improvement of photogenerated carrier separation efficiency. To be more specific, the formed built-in electric field is significantly intensified by producing the temperature difference potential between In2Se3 and PCN owing to the photothermoelectric effect of In2Se3, which actuates the high-efficiency separation of photogenerated charge carriers along the Z-scheme transfer path in the In2Se3/PCN heterojunction. The effective strategy of enhancing the built-in electric field to drive photogenerated charge separation proposed in this work opens up an innovative avenue to design Z-scheme heterojunction applied to high-efficiency photocatalytic reactions, such as hydrogen generation from water splitting, CO2R, and degradation of organic pollutants.