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

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.