Asymmetric empty orbitals in ZrO2-BCN for enhancing electrocatalytic hydrogenation of nitrogen to ammonia

Abstract

Electrocatalytic nitrogen reduction reaction (NRR) provides an environment-friendly and sustainable approach for nitrogen fixation at ambient conditions. However, simultaneously activating N≡N triple bond and suppressing the competitive hydrogen evolution reaction (HER) in aqueous electrolytes remain challenges. Herein, we construct ZrO2-BCN hetero-catalyst with tunable Zr-B-N interfacial structure for efficiently improving selectivity of the NRR. The asymmetric electron acceptance and back-donation capacity of the empty orbitals of Zr and B favors the activation of the N≡N triple bond during the NRR. The optimal ZrO2-BCN catalyst exhibits excellent NRR performance with a high ammonia yield of 17.8 μg mg-1cat. h−1 at −0.65 V vs. reversible hydrogen electrode (RHE) and a faradaic efficiency of 23.1 % at −0.45 V vs. RHE in 0.1 M HCl electrolyte, surpassing most previous reports. In-situ electrochemical attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy demonstrates the effect of the Zr-B-N interface on activating N2. This study paves a new way for hetero-interface catalyst design that would accelerate the implementation of NRR technology.