Cu/PCN Metal-Semiconductor Heterojunction by Thermal Reduction for Photoreaction of CO(2)-Aerated H(2)O to CH(3)OH and C(2)H(5)OH

[Image: see text] g-C(3)N(4)-based materials show potential for photoreduction of CO(2) to oxygenates but are subjected to fast recombination of photogenerated charge carriers. Here, a novel Cu-dispersive protonated g-C(3)N(4) (PCN) metal-semiconductor (m-s) heterojunction from thermal reduction of a Cu(2)O/PCN precursor was prepared and characterized using in situ X-ray diffraction, scanning transmission electron microscopy, X-ray photoelectron spectroscopy, ultraviolet–visible (UV–vis) spectra, photoluminescence (PL) spectra, transient photocurrent response, and electrochemical impedance spectroscopy (EIS). The Cu amount in Cu/PCN and the reduction temperature affected the generation of CH(3)OH and C(2)H(5)OH from the photoreaction of CO(2)-aerated H(2)O. During calcination of Cu(2)O/PCN in N(2) at 550 °C, Cu(2)O was completely reduced to Cu with even dispersion, and a m-s heterojunction was obtained. With thermal exfoliation, Cu/PCN showed a specific surface area and layer spacing larger than those of PCN. Cu/PCN-0.5 (12.8 wt % Cu) exhibited a total carbon yield of 25.0 μmol·g(–1) under UV–vis irradiation for 4 h, higher than that of Cu(2)O/PCN (13.6 μmol·g(–1)) and PCN (6.0 μmol·g(–1)). The selectivity for CH(3)OH and C(2)H(5)OH was 51.42 and 46.14%, respectively. The PL spectra, transient photocurrent response, and EIS characterizations indicated that Cu/PCN heterojunction promotes the separation of electrons and holes and suppresses their recombination. The calculated conduction band position was more negative, which is conducive to the multielectron reactions for CH(3)OH and C(2)H(5)OH generation.