In‐Situ Characterization Technologies for Electrocatalytic Reduction nitrate to Ammonia on Copper‐Based Catalysts

Abstract The excess nitrate (NO 3 − ) in water mainly comes from agricultural fertilization and industrial wastewater, which breaks the nitrogen balance and poses a serious threat to the environment and human health. Driven by renewable energy, the electrocatalytic NO 3 − reduction to ammonia (NH 3 ) (ENO 3 RA) is an environmentally friendly and sustainable technology. Due to its special structure, copper (Cu) is currently one of the best catalysts for ENO 3 RA, but the reaction mechanism and the structure–activity relationships of catalysts are still not clear enough. In‐situ characterization is a powerful tool to gain insight into the reaction process. This review introduces several types of in‐situ techniques such as in‐situ XAS, in‐situ FTIR and in‐situ DEMS, summarizes five pathways for converting *NO as the key intermediate to NH 3 during ENO 3 RA on Cu‐based catalysts. The research progress of Cu‐based electrocatalysts in recent years is sorted out from the aspects of composition and structure, and the catalytic mechanisms are discussed with the help of in‐situ characterization technologies. This review would be of help to provide reference characterization methods for exploring the mechanism and the design of electrocatalysts for ENO 3 RA.