Engineering CuMn Prussian blue analog-shelled nanobox for efficient electrochemical reduction of nitrate to ammonia

Electrocatalytic nitrate reduction reaction（ENRR） for ammonia synthesis is a promising strategy to relieve nitration contamination,as well as an alternative to the Haber-Bosch process.Prussian blue analogs（PBAs） are expected to be an electrocatalytic material with superior performance owing to their abundant active sites and open channel structure.However,most reported PBA materials possess low nitrate conversion and ammonia yield rates,which has led to a hindrance in their research of ENRR.Herein,CuMn-PBA-shelled nanoboxes（CuMn-PBA SNBs） synthesized through tannic acid etching and cation exchange approaches are demonstrated for efficient ammonia production.The optimal CuMn-PBA SNBs electrode achieves a high nitrate conversion of 91.33% and ammonia selectivity of 98.87% in a 0.2 mol·L-1 Na2SO4 solution with100×10-6 NO3--N at-1.4 V vs.SCE.Furthermore,the CuMn-PBA SNB s electrode exhibits exceptional stability throughout a 30 h electrocatalytic process.The outstanding electrochemical performance is attributed to the unique hollow nanobox structure with abundant active sites and high-throughput transport pathways for ions' aspects.