One-Step Synthesis of TiO₂/FeO(OH) Nano-Heterostructures as Electrocatalysts for the Oxygen Evolution Reaction

Transition metal compounds are abundant on Earth and are cost-effective materials. However, their inherent characteristics of low electrical conductivity and low electrocatalytic activity greatly limit their applications as electrocatalysts. In this study, we successfully synthesized TiO₂/FeO(OH) nanocomposite materials rich in heterogeneous structures using a one-step hydrothermal method and obtained nanostructured TiO₂/FeO(OH)-2 with excellent electrocatalytic oxygen evolution reaction (OER) performance by adjusting the ratio of Ti elements. The opposite charge regions at the heterojunction interface led to the reconstruction of the built-in electric field, accelerating electron transfer, optimizing the electronic structure during the catalytic reaction process, and ensuring the stability of surface charged active center sites in the heterojunction. Furthermore, in situ Raman measurements confirmed the crucial role of the built-in electric field in the electrocatalytic OER process of the TiO₂/FeO(OH)-2 nano-heterostructure. The density functional theory calculations further confirmed the promotional effect of the heterogeneous interfaces constructed in TiO₂/FeO(OH)-2 on the OER activity and also revealed that the intermediate *OOH is the rate-determining step of the OER reaction. The optimized TiO₂/FeO(OH)-2 composites with p-n heterojunctions featuring nanorod and nanosphere structures recorded an overpotential of 262 mV at 10 mA cm^-2 and exhibited sustained effectiveness over a 100 h period at an overpotential of 300 mV. This study not only provides a simple method for constructing p-n type heterogeneous structure materials but also in situ characterizes the role of heterojunction interfaces in the mechanism of electrocatalytic OER.