Engineered Electron-Deficient Sites at Boron-Doped Strontium Titanate/Electrolyte Interfaces Accelerate the Electrocatalytic Reduction of N 2 to NH 3 : A Combined DFT and Experimental Electrocatalysis Study.

The development of an efficient, selective, and durable catalysis system for the electrocatalytic N 2 reduction reaction (ENRR) is a promising strategy for the sustainable production of ammonia. The high-performance ENRR is limited by two major challenges: poor adsorption of N 2 over the catalyst surface and abysmal N 2 solubility in aqueous electrolytes. Herein, with the help of our combined density functional theory (DFT) calculations and experimental electrocatalysis study, we demonstrate that concurrently induced electron-deficient Lewis acid sites in an electrocatalyst and in an electrolyte medium can significantly boost the ENRR performance. The DFT calculations, ex situ X-ray photoelectron and FTIR spectroscopy, electrochemical measurements, and N 2 -TPD (temperature-programmed desorption) over boron-doped strontium titanate (BSTO) samples reveal that the Lewis acid-base interactions of N 2 synergistically enhance the adsorption and activation of N 2 . Besides, the B-dopant induces the defect sites (oxygen vacancies and Ti 3+ ) that assist in enhanced N 2 adsorption and results in suppressed hydrogen evolution due to B-induced electron-deficient sites for H + adsorption. The insights from the DFT study evince that B prefers the Sr top position (on top of Sr) where N 2 adsorbs in an end-on configuration, which favors the associative alternating pathway and suppresses the competitive hydrogen evolution. Thus, our combined experimental and DFT study demonstrates an insight toward enhancing the ENRR performance along with the suppressed hydrogen evolution via concurrently engineered electron-deficient sites at electrode and electrolyte interfaces.