Asymmetric Pulsed Electrolysis Enhances Nitrate-to-Ammonia Electroreduction via Optimizing the Local Reaction Microenvironment

Pulsed electrolysis is widely regarded as a promising strategy for enhancing the performance of the electrocatalytic nitrate reduction reaction (NO3–RR). However, research on the effect of symmetric and asymmetric pulsed electrolysis on the NO3–RR remains elusive. Here, the CuMn alloy serves as a model catalyst to systematically investigate the impact of symmetric and asymmetric pulsed electrolysis on the performance of NO3–RR. A series of operando measurements and control experiments indicate that a suitable asymmetric pulsed electrolysis can optimize the local microenvironment of the NO3–RR, including optimizing the coverage of NO3–, enhancing the generation of key N-containing intermediates, and inhibiting the hydrogen evolution reaction, thereby improving the Faradaic efficiency and yield rate of NH3. Consequently, the Faradaic efficiency and yield rate of NH3 for the optimal asymmetric pulsed electrolysis between a less negative potential time of 2 s and a more negative potential time of 4 s are 94.03% and 9.13 mg h–1 cm–2, respectively, which are 1.42-fold and 2.10-fold higher than those of static electrolysis. Moreover, the Faradaic efficiency of NH3 for the optimal asymmetric pulsed electrolysis was 66.32% at a lower concentration of NO3– (2000 ppm), which is 1.73-fold higher than that of static electrolysis, indicating that the performance of asymmetric pulsed electrolysis is further enhanced in the lower concentration of NO3–, further confirming that asymmetric pulsed electrolysis is a feasible strategy to improve the performance of the NO3–RR.