Ultrathin manganese oxides enhance the electrocatalytic properties of 3D printed carbon catalysts for electrochemical nitrate reduction to ammonia

Electrochemical nitrate reduction reaction (NO₃RR) is a promising approach to remedying the environmental pollution from nitrate, and simultaneously a sustainable alternative to traditional Haber-Bosch process especially for decentralized ammonia production. Here, we firstly explore the electrocatalytic activity of two 3D printed carbon frameworks consisting of 0-dimentional (0D) carbon black and 1-dimentional (1D) carbon nanotubes towards cost-efficient electrocatalysts for NO₃RR. Different from the electrocatalytic inert properties of 0D carbon framework, 1D carbon framework exhibits the electrocatalytic activity for NO₃RR with a Faradaic efficiency of more than 50% at − 1.21 V vs. RHE. Control experiments suggest that such activity originates from the synergistic electrocatalytic contributions between intrinsic surface features of carbon nanotubes and metallic impurities. Since the content and distribution of these metallic impurities are unpredictable, an ultrathin deposit of electrocatalytic manganese oxides is further deposited by atomic layer deposition on 1D carbon framework to ensure well defined surfaces for effective NO₃RR. The proposed strategy by integrating 3D printing of conductive carbon framework with atomic layer deposition of an electrocatalytic layer provides a feasible electrode fabrication for electrochemical NO₃RR and shows a promising prospect in the electrocatalytic field.