Dynamic Evolution of Co Species and Morphological Reconstruction on Co-N-C During the Nitrate Reduction Reaction in Neutral Electrolyte

The electrochemical nitrate reduction reaction (eNO3-RR) is considered an effective approach for converting nitrate-containing wastewater to ammonia. The adsorption and activation of NO3- is the critical step for many materials, and the high energy barrier inhibits the continuation of the reduction reaction. The Co nanoparticles encapsulated in the carbon layer we prepared spontaneously react with NO3-, and the resulting Co2+ is then reduced by electroreduction to Co0, which circulates continuously. This resulted in overcoming the energy input required for NO3- adsorption and conversion, thereby increasing the catalytic activity. At the same time, the morphology of the catalyst reconstructed from a dodecahedron to a nanosheet structure, and the increased surface area also gives it better properties. The obtained Co(OH)2@Co-N-C has an excellent eNO3-RR of 2774.7 μg h-1 cm-2 with a Faraday efficiency of 81.4% in neutral solution. Our work provides a new idea for the design of Co-based catalysts for eNO3-RR.