Ambient and Selective Electrochemical Dinitrogen Fixation to NH3 Catalyzed by Microporous Organic-Inorganic Hybrid Copper Phosphonate

Abstract

Despite great efforts, developing a stable and efficient electrocatalyst with prevailing activity for the electrochemical N2 reduction reaction (NRR) to NH3 under ambient conditions is still a burgeoning challenge. Here, we present a new microporous organic-inorganic hybrid copper phosphonate (CuPn) electrocatalyst with outstanding stability and selectivity toward NRR. The high surface area combined with microporous channels of CuPn provides excellent faradaic efficiency of 28.32% at -0.65 V vs reversible hydrogen electrode (RHE) for NRR with a high NH3 yield rate of 73.9 mu g h-1 mgcat -1 at -0.7 V vs RHE. The resulting superior catalytic activity can be ascribed to the porous structure of the material and active Cu catalytic centers. The isotopic labeling experiments and consequent qualitative and quantitative 1H NMR analyses verified that the ammonia is derived from the electrochemical NRR process. The density functional theory (DFT) study reveals that the associative alternating pathway, with the first protonation step of *N2 to form *NNH as the potential-determining step, offers the most favorable route for electrochemical NRR over the as-prepared microporous CuPn.