Amorphization engineering of Ni-cysteine coordination composition for urea electro-oxidation at large current density

Unavoidable oxygen evolution reaction (OER) and the relatively high potential to form real active sites of Ni³⁺ species severely decrease the efficiency of urea-assisted hydrogen generation facility. Herein, amorphization Ni-cysteine coordination (aNi-cys) is constructed as efficient urea electro-oxidation reaction (UOR) catalyst with highly capable of suppressing competitive OER and promoting the Ni²⁺ to Ni³⁺ in-situ electrochemical configuration through deliberately regulating the Ni/l-cysteine coordination environment. The abundant ligand atoms (N, S, and O) of l-cysteine considerably tuned the Ni electronic structure to the most suitable state while the amorphization thin lamellas increased the exposed active sites and befitting for the access of electrolyte to electrode surface, resulting improved UOR activity with a large peak current density of 263 mA cm^-2, far exceeding crystalline Ni-cysteine coordination (cNi-cys) and long-term stability for 50 h working. Excitingly, only 41 kWh is required to produce 1 kg H₂ (50 mA cm^-2) from a home-made urea-assisted simulated seawater electrolysis apparatus, about 8 kWh energy saving from that of water splitting. This work gives a clue for preparing advanced electrocatalysts applicable to urea-related energy system with large current density.