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.

Automated summary

Electrochemical nitrate reduction reaction (NO3RR) is a promising method for addressing nitrate pollution and an alternative to traditional ammonia production. This study explores the electrocatalytic activity of 3D printed carbon frameworks consisting of carbon black and carbon nanotubes for NO3RR. The 1D carbon framework exhibits higher electrocatalytic activity with a Faradaic efficiency of over 50% at -1.21 V vs. RHE, attributed to synergistic electrocatalytic contributions between carbon nanotubes and metallic impurities. An ultrathin deposit of electrocatalytic manganese oxides is further added to ensure well-defined surfaces for effective NO3RR. This integrated approach shows promise for electrode fabrication and electrochemical NO3RR.