Metal-Free Carbon Catalysts for Cathodic Electro-Synthesis into Value-Added Products via Oxygen, Nitrogen, and...

Electrochemical cathodic reductions offer promising approaches for the green synthesis of value-added chemicals, including hydrogen peroxide (H₂O₂) and ammonia (NH₃). Compared with traditional processes, the decentralized electro-synthesis enables on-site production with minimal carbon footprint. In these systems, cathodic catalysts critically govern the overall activity and selectivity of these multi-step reactions. Among the various reported catalysts, carbon-based metal-free electrocatalysts (C-MFECs) have attracted extensive attention, owing to their high conductivity, structural tunability, chemical stability, and eco-friendliness. Given the shared principles in material design and synthesis, this review systematically summarizes recent advances in C-MFECs for H₂O₂ and NH₃ electro-synthesis via oxygen, nitrogen, and nitrate reduction reactions. Special focus is placed on the design strategies for C-MFECs, demonstrating universal understandings of non-metal doping and defect construction in these important reactions. In addition, innovations in electrode architecture and reactor configuration are highlighted to address challenges in achieving high current densities and efficient product separation. Finally, major challenges and perspectives specific to C-MFECs in oxygen, nitrogen, and nitrate electroreductions are highlighted to inform future advances in H₂O₂ and NH₃ electro-synthesis.