Pauling-type adsorption of O₂ induced by S-scheme electric field for boosted photocatalytic H₂ O₂ production

The effective adsorption of oxygen (O2 ) molecules over photocatalysts is a critical step in promoting the performance of photocatalytic H2 O2 production. However, g-C3 N4 usually features a Yeager-type (side-on) adsorption configuration of O2 molecules, which causes the breaking of O-O bonds and severely hinders the H2 O2 production activity. Herein, we synthesized an oxygen-vacancy-rich TiO2-x /g-C3 N4 step-scheme (S-scheme) heterojunction to regulate the oxygen adsorption configuration and improve the 2e- ORR selectivity of H2 O2 production. In-situ X-ray photoelectron spectroscopy (in-situ XPS) and density functional theory (DFT) calculations reveal that the S-scheme heterojunction is formed between TiO2-x and g-C3 N4 . The difference between their Fermi levels leads to the electron flow from g-C3 N4 to TiO2-x , which increases the electron-deficient sites in g-C3 N4 . As a result, the cleavage of O-O bonds on the surface of g-C3 N4 is avoided and the oxygen adsorption configuration is tuned from Yeager-type to Pauling-type (end-on). Consequently, the photocatalytic H2 O2 production rate is dramatically improved to 1780.3 mu mol h-1 , which is about 5 times higher than that of pristine g-C3 N4 . This work paves a new way to tailor the oxygen adsorption configuration by rationally designing S-scheme heterojunction photocatalysts. (c) 2024 Published by Elsevier Ltd on behalf of The editorial office of Journal of Materials Science & Technology.