Surface doping of cobalt nanoparticles by selenium anion to steer the selectivity in electrocatalytic nitrate reduction†
Abstract
Electrocatalytic nitrate reduction to ammonia (NO3RR) not only effectively removes the nitrate contamination from the wastewater but also provides high-valued ammonia products for industrial applications. The design of NO3RR catalysts with moderate hydrogen-absorbing strength is urgently needed to facilitate the complete hydrogenation of intermediate products while minimizing undesired hydrogen evolution reaction (HER). Herein, we report a surface modification strategy to optimize the performance of cobalt nanoparticles through surface Se doping (Se@Co NPs) while maintaining the metallic state of Co NPs to ensure conductivity for electron transfers. The Se@Co NPs supported on carbon nanofibers (Se@Co/CNFs) exhibit a high NH3 Faraday efficiency (FE) of 94.8% and a production rate of 3.6 mmol h−1 mgcat−1 at −0.9 V vs. RHE under ambient conditions. Theoretical calculations show that Se doping on the Co surface reduces the binding strength of Co active sites with *NO, thereby reducing the energy barriers of the rate-determining step (RDS) (*NO → *NOH) in electrocatalytic NO3RR and inhibiting the competitive HER.