Modulation of Lewis and Brønsted Acidic Sites to Enhance the Redox Ability of NbO Photoanodes for Efficient Photoelectrochemical Performance.

Accelerated surface redox reaction and regulated carrier separation are the crux to the development of highly reactive oxide semiconductors for efficient photoelectrochemical water splitting. Here, we have selected NbO materials that combine unique surface acidity and semiconductor properties, and first used surface phosphorylation to change its surface acidic sites (Lewis and Brønsted acidic sites) to achieve efficient photoelectrochemical water splitting. The resulting photoanode born from this strategy exhibits a high photocurrent density of 0.348 mA/cm at 1.23 V, which is about 2-fold higher than that of the bare NbO, and a cathodic shift of 60 mV. Detailed experimental results show that the large increase in the Lewis acidic site can effectively modulate the electronic structure of the active sites involved in catalysis in [NbO] polyhedra and promote the activation of lattice oxygen. As a result, higher redox properties and the ability to inhibit carrier recombination are exhibited. In addition, the weakening of the Brønsted acidic site drives the reduction of protons in the oxygen evolution reaction (OER) and accelerates the reaction kinetics. This work advances the development of efficient photoelectrochemical water splitting on photoanodes driven by the effective use of surface acidity and provides a strategy for enhancing redox capacity to achieve highly active photoanodes.