Localized enriching nitrate/proton on reconstituted Fe nanoparticles boosting electrocatalytic nitrate reduction to ammonia

The electrochemical conversion of nitrate,a widespread water pollutant,into valuable ammonia represents a green and decentralized approach to ammonia synthesis.However,the sluggish multielectronproton coupling path and the low reactive species（nitrate and proton） concentration at the catalyst interface inhibit the efficiency of ammonia production from nitrate reduction reaction（NitRR）.Herein,we introduce a novel iron-based tandem catalyst encapsulated by reduced graphene oxide（denoted as Fe-rGO）,with a superior ammonia production rate of 47.815 mg h-1 mgcat-1 and a high Faraday efficiency（FE） of 96.51% at an applied potential of-0.5 V.It also delivers a robust stability with FE above90% under a current density of 250 mA cm-2 for 50 h.In situ X-ray absorption spectroscopy reveals that the FeOx is dynamically translated to Fe0 site concurrently with the enhancement of the NH3 production rate,suggesting the Fe0 site as hydrogenation active center.The asymmetric distribution of surface charges of rGO not only enriches nitrate ions at the catalytic interface and promotes the hydrogenation process in NitRR,but also protects the iron species and ensures their stability during electrolysis.The Zn-NO3-battery demonstrates an impressive FE of 88.6%,highlighting its exceptional potential for practical applications.