Accelerating solid-liquid interfacial hole transfer kinetics through designed flower-like trivalent bismuth crystallite island for photoelectrochemical application

Abstract

Hematite (Fe2O3) is an appealing photoanode material for photoelectrochemical application due to its suitable band-gap. However, the serious electron-hole recombination of hematite results in the photocurrent density generated is lower than the theoretical value. In this work, we loaded flower-like trivalent bismuth crystallite islands onto nano Fe2O3 electrodes to improve photoelectrochemical application. The trivalent bismuth ions decorated hematite photoanode demonstrates excellent photocurrent density, rapid water oxidation kinetics, and remarkable bulk separation efficiency. Mott-Schottky results indicate that surface-treated hematite showed increased carrier density and enhanced uptrend band bending. Furthermore, the trivalent bismuth ions accelerate hole capture through Bi(III)/Bi(V) exchange, reducing the recombination of oxygen-related holes with surface trapping sites. Under simulated sunlight irradiation, the photocurrent density at 1.23 (vs. RHE) exhibits fourfold enhancement that of hematite film. This work demonstrates a new possibility that Bi(III) compounds, in a passivation-like form, can effectively improve carrier transport on the surface of hematite photoanodes.