Lithium/bismuth co-functionalized phosphotungstic acid catalyst for promoting dinitrogen electroreduction with high Faradaic efficiency

Abstract

Ammonia occupies a significant standing in the global economy. As a promising alternative to the energy-intensive Haber-Bosch process, electrochemical nitrogen reduction could achieve sustainable ammonia synthesis. However, the attractive alternative suffers from the bottleneck of insufficient activity and low electron selectivity. Here, we report an efficient electrocatalyst using phosphotungstic acid as platforms to anchor bismuth species on the 4-fold hollow site and anchor lithium species on the 3-fold hollow site, which reaches high ammonia yield rates of 61 ± 1 μg h −1 mg cat. −1 and Faradaic efficiencies of 85% ± 2% at −0.1 V versus reversible hydrogen electrode (RHE). Experiments and theoretical calculations reveal that the Bi δ+ species can promote the activation and hydrogenation of nitrogen at adjacent unsaturated tungsten active sites, and the incorporated lithium species reduce the hydrogen reduction rate in undesired water splitting. This synergistic functionalization of bismuth and lithium species contributes to the high-efficient catalyst. Li/Bi species are anchored on phosphotungstic acid by impregnation Li/Bi species synergistically contribute to the activation of nitrogen Li species are favorable to inhibit the competitive hydrogen evolution reaction Li/Bi species teamwork achieves a high Faradic efficiency for aqueous ammonia synthesis Electrochemical nitrogen reduction could achieve sustainable ammonia synthesis as a promising alternative to the energy-intensive Haber-Bosch process. Liao et al. design Li/Bi co-functionalized phosphotungstic acid by precisely anchoring Bi and Li species, where Bi δ+ species facilitate nitrogen reduction and Li species suppress competitive hydrogen evolution reaction. The cooperation promotes electrocatalytic nitrogen reduction to ammonia with, to the best of our knowledge, record Faradic efficiencies for aqueous systems.