Lattice-Engineered Nickel Oxide for Electrocatalytic Urea Recycling with Near-Unity N₂ Selectivity

Circulating nitrogen is crucial to the sustainability of our living system. Urea is a central form of nitrogen species that sustains our food supply, but its natural abundance in fertilizing effluent and human metabolite demands circulating technology back to innocuous dinitrogen (N₂), while it would otherwise pollute the environment. Electrochemical urea reforming can fragment the urea molecule into N₂ and dihydrogen (H₂) using renewable electricity, and N₂ can be formed directly via oxidative intramolecular N-N coupling on catalytic surfaces. However, this reforming technology remains elusive due to the low N₂ selectivity. Herein, we uncovered a urea oxidation pathway that selectively splits urea into N₂, driven by nickel oxide (NiO) lattices with adjacent Ni sites. The double-ended urea coordination on NiO facilitates intramolecular N-N coupling and suppresses C-N cleavage toward undesired overoxidation products. Further lattice engineering via Al substitution creates the optimal performance of near-unity N₂ selectivity toward N-based products and a 1 order of magnitude higher N₂ production rate compared to those of most reported catalysts. The electrochemical urea reforming devices can effectively split urea into N₂ and H₂ using both synthetic urea and artificial urine, reviving this technology as a bridge of sustainable energy and environmental treatment toward the water-energy-food nexus.