Effect of Co Addition in Amorphous Ni-Based Alloys for the Alkaline Oxygen Evolution Reaction

摘要

An amorphous alloy Ni_(74.2)Co_5Nb_(12.5)Y_(8.3) was synthesized using cryogenic mechanical alloying and evaluated as a catalyst for the oxygen evolution reaction (OER) in alkaline media using cyclic voltammetry and Tafel measurements. Electrochemical testing showed that the amorphous alloy possessed a lower Tafel slope and enhanced kinetics for the OER compared to crystalline Ni and Ni_(95)Co_5. Anodic cycling of the amorphous alloy resulted in a lower onset potential for the OER and decreased Tafel values while no changes were observed for crystalline Ni_(95)Co_5. Pairing of in situ confocal Raman spectroscopy with anodic cycling showed that the amorphous alloy formed reversible hydrous Co oxy/hydroxides instead of irreversible CoO_2 typically seen on crystalline NiCo alloys in KOH. The formation of hydrous Co oxy/hydroxides upon cycling was also accompanied by increased formation of β-NiOOH leading to enhanced catalytic performance of the amorphous alloy over the crystalline counterparts.