An oxygen vacancy-rich two-dimensional Au/TiO2 hybrid for synergistically enhanced electrochemical N2 activation and reduction

Abstract

The electrochemical nitrogen reduction reaction (NRR) is emerging as a promising sustainable technique that can convert nitrogen (N₂) to ammonia (NH₃) under ambient conditions. However, the selectivity and electrocatalytic activity of the NRR obtained experimentally to date are still unsatisfactory. As a consequence, it remains a technical challenge to develop scalable, low-cost, and efficient NRR electrocatalysts. Herein, we present an oxygen vacancy (V_O)-rich two-dimensional gold (Au)/titanium dioxide (TiO₂) hybrid that acts as an advanced NRR electrocatalyst under ambient conditions. Electrocatalytic testing demonstrated that the Au/TiO₂ hybrid catalyst delivered a promising NH₃ yield of 64.6 μg h⁻¹ mg⁻¹ cat and a high faradaic efficiency of 29.5% at −0.40 V versus the reversible hydrogen electrode in acidic media. Experimental findings and theoretical calculations demonstrate that the strong electron-donating effect of V_O in TiO₂ was essential for N₂ activation. Meanwhile, the introduction of Au promotes both the electrochemical and thermodynamic rate-limiting steps by adjusting the electronic structure of the active sites. Together, these effects greatly facilitate the activation and reduction of N₂ under ambient conditions. The specific catalyst design strategy in our work represents an alternative avenue to produce other two-dimensional electrocatalysts with high NRR activity and selectivity through rational structural engineering.