Interfacial hydrogen bond modulation of dynamic catalysts for nitrate electroreduction to ammonia

Abstract

Electrocatalytic nitrate reduction (NO3−RR) shows potentials in clean NH3 synthesis and industrial effluent disposal, turning waste into treasure. However, the catalyst reconstruction mechanism is still ambiguous, and the influence of interfacial hydrogen bond on NO3−RR performance remains unexplored. Herein, a Cr doping strategy is developed to regulate interfacial hydrogen-bonded interactions on the Co-based dynamic electrocatalyst for improving electrocatalytic NO3−RR activity. In-situ XRD, in-situ Raman and theoretical calculations indicate that doping Cr can modulate the reconstruction process of the Co-based material, achieving the dynamic balance of Co(OH)2 and Co. Moreover, molecular dynamics simulations, density functional theory calculations combined with in-situ infrared spectra reveal that strong hydrogen-bonded interactions between interfacial H2O and the Cr doped Co(OH)2 surface can drag more free H2O from rigid H2O network and facilitate the H2O dissociation with the formation of active hydrogen for accelerating the NO3−RR pathway on metallic Co site. As a result, the Cr doped Co-based dynamic electrocatalyst can display a superior NH3 Faradaic efficiency of 97.36% and a high NH3 yield rate of 58.92 mg h-1 cm-2, outperforming the state-of-art electrocatalysts. This work can further inspire the dynamic electrocatalyst design and interfacial microenvironment modulation for electrochemical hydrogenation reactions.