Pauling-type adsorption of O2 induced by S-scheme electric field for boosted photocatalytic H2O2 production

The effective adsorption of oxygen (O 2 ) molecules over photocatalysts is a critical step in promoting the performance of photocatalytic H 2 O 2 production. However, g-C 3 N 4 usually features a Yeager-type (side-on) adsorption configuration of O 2 molecules, which causes the breaking of O–O bonds and severely hinders the H 2 O 2 production activity. Herein, we synthesized an oxygen-vacancy-rich TiO 2– x /g-C 3 N 4 step-scheme (S-scheme) heterojunction to regulate the oxygen adsorption configuration and improve the 2e – ORR selectivity of H 2 O 2 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 TiO 2– x and g-C 3 N 4 . The difference between their Fermi levels leads to the electron flow from g-C 3 N 4 to TiO 2– x , which increases the electron-deficient sites in g-C 3 N 4 . As a result, the cleavage of O–O bonds on the surface of g-C 3 N 4 is avoided and the oxygen adsorption configuration is tuned from Yeager-type to Pauling-type (end-on). Consequently, the photocatalytic H 2 O 2 production rate is dramatically improved to 1780.3 μmol h –1 , which is about 5 times higher than that of pristine g-C 3 N 4 . This work paves a new way to tailor the oxygen adsorption configuration by rationally designing S-scheme heterojunction photocatalysts.