Transforming Carnation-Shaped MOF-Ni to Ni–Fe Prussian Blue Analogue Derived Efficient Bifunctional Electrocatalyst for Urea Electrolysis

Compared with the oxygen evolution reaction (OER), the urea oxidation reaction (UOR) is more likely to react in an alkaline electrolyte, and the thermodynamic voltage of urea electrolysis is 0.37 V, which is much smaller than the theoretical voltage of water-splitting (1.23 V). In this work, a Ni–Fe Prussian blue analogue is grown on MOF-Ni by two steps. First, carnation-shaped MOF-Ni is directly grown on the nickel foam. Second, nanocube-like Prussian blue analogue is grown on a MOF-Ni template. After phosphating reaction in a tube furnace, Ni2P/Fe2P (denoted as MNPBA-P) is obtained. MNPBA-P can still maintain the initial structure of nanocubes on a carnation-shaped MOF-Ni, which causes it to have better conductivity and larger electrochemical active surface area. As a bifunctional catalyst, MNPBA-P has a good performance in the catalytic reaction of cathode and anode. It is worth noting that when 0.5 M urea was added to the electrolyte, the high anode overpotential is greatly improved. Compared with overall water-splitting, MNPBA-P assembled into an electrolyzer requires smaller cell voltage in urea electrolysis. MNPBA-P || MNPBA-P electrolyzer only needs 1.50 V to afford 10 mA cm–2 in urea electrolyte and has a good stability for 12 h.