Unlocking the potential of ruthenium catalysts for nitrogen fixation with subsurface oxygen

Abstract

As a clean, eco-friendly and sustainable process, electrocatalysis has potential to replace the energy-consuming and environment-polluting Haber–Bosch process for N₂ fixation. Although ruthenium (Ru) is generally considered as the best electrocatalyst for this process, its low faradaic efficiency greatly hampers the practical applications. Considering the solvent effects, our ab initio calculations and micro-kinetic simulations indicate that doping oxygen into the sublayer of Ru(0001) can turn some surface Ru⁰ atoms into positively charged Ru⁺, significantly boosting the reduction of N₂. The overpotential can be dramatically reduced to 0.18 V only for Ru(0001) with 1.00 ML subsurface oxygen. Notably, the calculated turnover frequency (TOF) is 3.64 × 10⁻² per s per site at 700 K and 100 bar, which is hundreds of times greater than that of the pure Ru(0001) surface. In terms of experimental progress on the successful incorporation of subsurface oxygen into the Ru(0001) surface, our work offers a practical and feasible route to boost electrochemical reduction of N₂ to ammonia.