Steering pH-Dependent Pathways on Unconventional Phase Alloy Nanostructures for Universal Nitrate Electroreduction.

Abstract

Electrocatalytic nitrate reduction reaction (NO₃RR) to ammonia has been regarded as a sustainable strategy for industrial wastewater denitrification and fertilizer manufacturing toward green nitrogen circulation. However, complex pH conditions of practical nitrate wastewater result in poor catalyst universality, severely hindering their long-term deployment. Furthermore, the underlying reaction mechanisms in different pH scenarios remain ambiguous, obstructing the rational design of pH-universal electrocatalysts. Here we propose a crystal phase engineering approach to enhance the NO₃RR performance in complex pH scenarios. The as-designed unconventional face-centered cubic (fcc) RuW nanoflowers exhibit excellent ammonia Faradaic efficiency (FE) above 91.0% over a wide pH range of 1-14, with the largest yield rate of 40.1 mg h^-1 mg_cat ^-1. Mechanism studies indicate that fcc RuW nanoflowers adaptively steer reaction pathways toward diverse pH environments. Based on the long-term durability test at an industrial-level current density of 300 mA cm^-2 for 200 h in flow reactors, techno-economic analysis with the optimized process further demonstrates promising application potential. This study not only provides a fundamental insight into the pH-dependent mechanisms of nitrate electroreduction, but also offers a robust catalyst design approach toward complex practical conditions.