N-Doped 3D Porous Ni/C Bifunctional Electrocatalysts for Alkaline Water Electrolysis

Water electrolysis offers a promising approach toward future sustainable energy mix utilizing hydrogen as energy carrier. Bifunctional catalyst which is active in both oxygen and hydrogen evolution reactions can significantly enhance total electrochemical water splitting efficiency and simplify electrolysis systems. In this study, nitrogen doped nickel-containing porous carbon networks were prepared to fulfill this role. Peptone was used as carbon and nitrogen source during the synthesis and NaCl presence as a template resulted in the formation of open mesopores interconnected by thin carbon sheets with nanosized Ni particles encapsulated in the carbon matrix. A low onset potential of 53 mV and a charge transfer resistance of 3.8 Ω with excellent cycling stability were demonstrated when the optimized catalyst Ni-2 was applied in HER. It was also shown that Ni-2 onset potential, charge transfer resistance, and durability in OER were comparable to those of a commercial RuO2 catalyst. During the electrolysis study conducted at 10 mA cm–2, Ni-2 maintained a cell voltage of 1.63 V with remarkable stability during 25 h operation.