Bifunctional photothermal effect to promote band bending and water oxidation kinetics for improving photoelectrochemical water splitting

Abstract

The photothermal effect is proved to favor the photoelectrochemical (PEC) water oxidation, but the impact of the photothermal effect on the band bending in the heterojunction has seldom been revealed. In this work, we constructed a Z schematic heterojunction by heteroatoms doping, the carbon quantum dots (CQDs) was anchored to trigger the local heat under the NIR irradiation. With the photothermal effect, the photocurrent density of (Ti, Zn)–Fe2O3@Ti–Fe2O3 reached 1.02 mA/cm2 (1.23 VRHE), 2.30 mA/cm2 (1.60 VRHE), which yielded an increased by 1.3 folds, 1.7 folds, respectively. Detailed studies showed that the photothermal effect would enlarge the contact potential difference in the heterojunction and band bending at the semiconductor-electrolyte interface (SEI). Furthermore, the oxygen evolution reaction (OER) kinetics was also accelerated, which was evidenced by the Tafel slope decreasing from 88 mV/decade to 78 mV/decade. Despite the photovoltage being reduced, the advantages of the photothermal effect still out weighted the disadvantages.