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

The electrochemical N2 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 N2 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 N2 fixation performances, with an ammonia production rate (8.90 µg·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.