Carbon-Based Catalysts for Selective Electrochemical Nitrogen-to-Ammonia Conversion

Abstract

Electrochemical nitrogen reduction reaction (NRR) to ammonia (NH3) driven by renewable electricity is a promising alternative to the current energy-intensive and fossil feedstock-dependent Haber–Bosch (H–B) process. The intrinsic inertness of N2 molecule and competition of hydrogen evolution reaction (HER) are the primary challenges for NRR. Although transition metal-based electrocatalysts can solve the kinetic limitation of N≡N activation through the π-back-donation process, the d-orbital electrons of transition metal atoms facilitate the formation of a metal-H bond, boosting the undesirable HER. Carbon-based materials featuring tunable electronic structures and facile formation of defects have significantly improved electrocatalytic NRR activity in the past few years. Therefore, a review on state-of-the-art carbon-based catalysts for NRR is timely to provide a summary of recent developments in theoretical and experimental aspects. In this review, various defect engineering strategies for the evolution of the desired carbon-based electrocatalysts are comprehensively summarized. The intrinsic relationships between the structures of the defective carbon materials and NRR performance are also discussed in detail. This review aims to stimulate greater interests for developing more efficient electrocatalysts for NRR in the future.