One-Step Molten Salt Constructing Double S-Scheme K0.2WO3/NiO/NiWO4 Heterojunction for Photocatalytic CO2 Reduction

Rapid charge separation and transfer is the key scientific problem in photocatalysis. The construction of S-scheme heterojunction is one of the effective strategies to promote charge separation and maintain the strong redox properties. Herein, the NiO, K0.2WO3, and NiWO4 ternary double S-scheme K0.2WO3/NiO/NiWO4 heterojunction (W/NiO) was created by a one-step molten salt method. Ultraviolet-visible (UV-Vis) diffuse reflectance spectra, photoluminescence (PL) spectra, photoelectrochemistry tests, and other analyses revealed that the double S-scheme heterostructure broadened the spectral response range of NiO and promoted its separation of photocarriers. Compared with pristine NiO, the modified double S-scheme heterojunction enhanced the surface adsorption of water molecules and the accumulation of intermediate product of HCOO−, and optimized the CO2 reduction system, realizing the improved CO yield of 373 μmol·g−1·h−1 in Ru(byp)32+/ethanolamine of CO2 reduction system. This study indicates that double S-scheme heterojunction could facilitate efficient photogenerated charge transfer and separation, thereby achieving high activity and selectivity for CO2 photoreduction. Our work provides a reference for the one-step construction of double S-scheme heterojunction.