Pulse driven and polypyrrole mediated microenvironment regulation synergistically achieve efficient conversion of nitrate to ammonia by copper oxide electrocatalsis

The electrocatalytic nitrate reduction reaction (NO₃RR) has emerged as a promising strategy for sustainable wastewater treatment and ammonia synthesis, yet remains challenged by sluggish kinetics and competing hydrogen evolution reaction (HER). Although Cu/Cu₂O heterojunctions derived from in situ electroreduction of copper oxide (CuO) catalysts can effectively accelerate the rate-limiting NO₃⁻ to NO₂⁻ conversion to enable efficient NH₃ production, such structures often suffer from structural instability under prolonged cathodic polarization. Herein, we present a dual-modulation strategy combining periodic cathodic-anodic potential pulses with polypyrrole (PPy) overlayer modification to address these limitations. The pulsed potential protocol facilitates the periodic reconstruction of electroactive Cu/Cu₂O interfaces, while the PPy-functionalized electrode optimizes the local microenvironment by enhancing low-concentration nitrate enrichment and hydride species accumulation, thereby promoting the critical NO₂⁻ to NH₃ transition. The synergistic strategy achieves 93.93 % nitrate conversion, 95.13 % NH₃ selectivity, and 87.29 % Faradaic efficiency (FE) under neutral conditions, with post-activation enhancements reaching 94.10 % nitrate conversion and 98.86 % FE, demonstrating its superior catalytic capability compared to state-of-the-art systems. This work establishes a paradigm for stabilizing transient catalytic interfaces via electrochemical pulse engineering coupled with polymer-mediated microenvironment control, advancing the rational design of robust electrocatalysts for sustainable ammonia synthesis and nitrate remediation.