High-performance nitrogen electroreduction at low overpotential by introducing Pb to Pd nanosponges

Abstract

Electrochemical N2 reduction reaction (NRR) under milder conditions has become more and more promising and attractive due to its simplicity, high energy conversion efficiency and no need for expensive agents. But the designed electrocatalysts at ambient conditions are insufficient in activity and Faraday efficiency (FE). Among these electrocatalysts, Pd-based materials are promising NRR electrocatalysts ascribed to they have nitrogen reduction activity at a low overpotential. However, poorly NH3 yields and FEs of Pd-based nanomaterials are still significant problems. Herein we report PdPb nanosponges that perform effectively electroreduction of N2 to NH3 under ambient conditions. It was found Pb element can inhibit the hydrogen evolution reaction (HER) of Pd and enhance NRR performance. According to our experiment, in 0.1 M HCl, the NH3 yield of PdPb/C was 25.68 μg mg−1cat h−1 (5.14 μg cm−2 h−1) at 0.05 V vs. RHE, and corresponding FE was 5.79 %, which is one of the most active materials at 0.05 V vs. RHE among the currently reported literature. Further reducing the voltage to more negative (−0.05 V vs. RHE), the NH3 yield increased to the highest value, 37.68 μg mg−1cat h−1 (7.54 μg cm−2 h−1), 8 times better than Pd/C (4.8 μg mg−1cat h−1). Moreover, this catalyst also shows a great stability after 10 h. Besides that, density functional theory (DFT) also corresponds to the experimental results. The introduction of Pb can effectively reduce *H adsorption, inhibit HER, decrease the *NNH generation free energy of NRR process and improve NRR activity. Surprisingly, our ideas can also be extended to other materials such as RuO2. It provides an excellent channel for the rational design of high-efficiency NRR electrocatalysts at ambient conditions in the future.