Magnetron sputtering tuned “π back-donation” sites over metal oxides for enhanced electrocatalytic nitrogen reduction

Abstract

As an environmentally-benign and sustainable option for NH₃ synthesis, the electrochemical nitrogen reduction reaction (NRR) is expected to replace the traditional Haber–Bosch process. Transition metals with empty d-orbitals achieve NRR activity via a “π back-donation” process. However, the problem in overcoming hydrogen evolution reaction (HER) competition makes the exploration of transition metal-based catalysts with relatively inferior HER activity worthwhile. The challenges lie in designing a rational structure for efficient NRR. Herein, Ni³⁺ and oxygen vacancies were synergistically integrated on NiO@TiO₂ by magnetron sputtering, which provide this transition-metal oxide-based (TMO-based) material with “π back-donation” behavior. Accordingly, NiO@TiO₂ exhibited NH₃ yield (∼10.75 μg h⁻¹ cm_cat.⁻²) and faradaic efficiency (∼9.83%), which are nearly 10-fold higher relative to those of TiO₂ in neutral media. This work provides an efficient strategy for engineering “π back-donation” sites, and holds great potential in exploring new TMO-based electrocatalysts.