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

•3D/2D In2Se3/PCN heterostructure is constructed by simple in situ growth process.•It shows the improved photocatalytic capacity for CO2 reduction to CO.•The enhanced performance primarily stems from high-efficiency charge separation.•The built-in electric field is intensified by photothermoelectric effect.•The separation of photogenerated carriers abides by Z-scheme transfer path.