Photochemical Conversion of Nickelocene to a Nickel–Carbon–Oxygen Electrocatalyst for the Oxygen Reduction Reaction

The oxygen reduction reaction (ORR) plays a critical role as a half-reaction in electrochemical energy storage and conversion technologies, such as metal-air batteries and regenerative fuel cells. Transition metal-based electrocatalysts have been recognized as inexpensive alternatives to platinum that afford excellent activity in the ORR. Nevertheless, achieving precise control over metal distribution at the atomic level to enhance the reaction kinetics remains challenging. Herein, a one-step laser synthesis strategy is used to create noble-metal-free electrocatalysts composed of a microporous nickel-doped carbon–oxygen matrix (Ni–C–O), which is further dispersed over a ketjenblack (KB) support. The as-prepared Ni–C–O/KB electrocatalyst demonstrates superior ORR activity in an alkaline electrolyte with onset and half-wave potentials of 0.90 and 0.79 V, respectively, and long-term operation durability superior to commercial Pt/C. Rotating ring-disk electrode measurements further confirm that Ni–C–O/KB possesses an extremely low H2O2 yield (<1.4%) over the potential range of 0.2 to 0.8 V, along with high four-electron selectivity. Impedance spectroscopy measurements indicate that Ni–C–O/KB exhibits a smaller charge transfer resistance value compared to the as-synthesized Ni–C–O electrocatalyst. The findings indicate that the dispersion of Ni–C–O on KB creates more effective active sites, enhances the adsorption/desorption capacity for oxygen intermediates, and promotes electron transfer during catalytic reactions, ultimately enhancing the electrocatalytic activity.