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

Abstract

Electrocatalytic nitrate reduction (NO₃⁻RR) holds significant potential for clean NH₃ synthesis and the treatment of industrial effluents, effectively converting waste into a valuable resource. However, the catalyst reconstruction mechanism remains ambiguous, and the influence of interfacial hydrogen bonds on NO₃⁻RR performance remains underexplored. Herein, a Cr-doping strategy was developed to regulate the interfacial hydrogen-bonded interactions on Co-based dynamic electrocatalysts to improve electrocatalytic NO₃⁻RR activity. In situ XRD, in situ Raman spectroscopy and theoretical calculations indicated that Cr doping could modulate the reconstruction process of Co-based materials, achieving a dynamic balance between Co(OH)₂ and Co. Moreover, molecular dynamics simulations and density functional theory calculations, combined with in situ infrared spectroscopy, revealed that the strong hydrogen-bonding interactions between interfacial H₂O and the Cr-doped Co(OH)₂ surface could drag more free H₂O from the rigid H₂O network and facilitate H₂O dissociation, forming active hydrogen to accelerate the NO₃⁻RR pathway on metallic Co sites. As a result, the Cr-doped Co-based dynamic electrocatalyst displayed 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-the-art electrocatalysts. This work can further inspire the design of dynamic electrocatalysts and the modulation of the interfacial microenvironment for promoting effective electrochemical hydrogenation reactions.