Single‐entity Electrochemistry Unveils Dynamic Transformation during Tandem Catalysis of Cu2O and Co3O4 for Converting NO3− to NH3

Abstract Electrochemically converting nitrate to ammonia is an essential and sustainable approach to restoring the globally perturbed nitrogen cycle. The rational design of catalysts for the nitrate reduction reaction (NO 3 RR) based on a detailed understanding of the reaction mechanism is of high significance. We report a Cu 2 O+Co 3 O 4 tandem catalyst which enhances the NH 3 production rate by ≈2.7‐fold compared to Co 3 O 4 and ≈7.5‐fold compared with Cu 2 O, respectively, however, most importantly, we precisely place single Cu 2 O and Co 3 O 4 cube‐shaped nanoparticles individually and together on carbon nanoelectrodes provide insight into the mechanism of the tandem catalysis. The structural and phase evolution of the individual Cu 2 O+Co 3 O 4 nanocubes during NO 3 RR is unveiled using identical location transmission electron microscopy. Combining single‐entity electrochemistry with precise nano‐placement sheds light on the dynamic transformation of single catalyst particles during tandem catalysis in a direct way.