Modulating the Oxidation State of Titanium via Dual Anions Substitution for Efficient N2 Electroreduction.

ABSTRACT

The electrocatalytic nitrogen reduction reaction (NRR) is a promising approach for renewable ammonia synthesis but remains significantly challenging due to the low yield and poor selectivity. Herein, a facile N and S dual anions substitution strategy is developed to tune the Ti oxidation states of TiO2 nanohybrid catalyst (NS-TiO2 /C), in which anatase TiO2 nanoplates with dense Ti3+ active sites are uniformly dispersed on porous carbon derived from 2D Ti3 C2 Tx nanosheets. The catalyst NS-TiO2 /C exhibits a superior ambient NRR efficiency with an NH3 yield rate of 19.97 µg h-1 mg-1cat and Faradaic efficiency of 25.49% and is coupled with a remarkable 50 h long-term stability at -0.25 V versus RHE. Both experimental and theoretical results reveal that the N and S dual-substitution effectively regulate the Ti oxidation state and electronical properties of the NS-TiO2 /C via simultaneously forming interstitial and substitutional TiS and TiN bonds in the anatase TiO2 lattice, inducing oxygen vacancies and dense Ti3+ active species as well as better electronic conductivity, which substantially facilitates N2 chemisorption and activation, and reduces the energy barrier of the rate-determining step, thereby essentially boosting NRR efficiency. This work provides a valuable approach to the rational design of advanced materials by modulating oxidation states for efficient electrocatalysis.