Doping strain induced bi-Ti3+ pairs for efficient N2 activation and electrocatalytic fixation

The electrochemical N-2 fixation to produce ammonia is attractive but significantly challenging with low yield and poor selectivity. Herein, we first used density function theory calculations to reveal adjacent bi-Ti3+ pairs formed on anatase TiO2 as the most active electrocatalytic centers for efficient N-2 lying-down chemisorption and activation. Then, by doping of anatase TiO2 with Zr4+ that has similar d-electron configuration and oxide structure but relatively larger ionic size, the adjacent bi-Ti3+ sites were induced and enriched via a strained effect, which in turn enhanced the formation of oxygen vacancies. The Zr4+-doped anatase TiO2 exhibited excellent electrocatalytic N-2 fixation performances, with an ammonia production rate (8.90 mu g.h(-1).cm(-2)) and a Faradaic efficiency of 17.3% at -0.45 V versus reversible hydrogen electrode under ambient aqueous conditions. Moreover, our work suggests a viewpoint to understand and apply the same-valance dopants in heterogeneous catalysis, which is generally useful but still poorly understood.