Transition-Metal-Substituted Cobalt Carbonate Hydroxide Nanostructures as Electrocatalysts in Alkaline Oxygen Evolution Reaction

Tuning of morphology and the electronic structure through substitution in the crystal lattice can enhance the performance of electrocatalysts. In view of this, the present work is focused on one-step hydrothermal fabrication of graphite paper (GP)-supported cobalt carbonate hydroxide (Co2(CO3)(OH)2/GP) nanostructures and its nickel- and manganese-substituted products, Co1.9Ni0.1(CO3)(OH)2/GP and Co0.95Mn0.05CO3/GP, respectively. This is followed by the investigation of their crystal structure, morphology, and electrocatalytic oxygen evolution activity. Our findings showed modification of the electronic structure in substituted cobalt carbonate hydroxides. In addition, specific and electrochemically active surface areas were also enhanced in Co1.9Ni0.1(CO3)(OH)2/GP and Co0.95Mn0.05CO3/GP compared to pure Co2(CO3)(OH)2/GP. It was noted that Ni- and Mn-substituted Co2(CO3)(OH)2 exhibited dramatically enhanced oxygen evolution reaction (OER) performance in 1.0 M KOH. In addition, the mechanism of the OER was explored experimentally to reveal the origin of their enhanced electrocatalytic activity. Our findings also established the relatively superior performance of Co1.9Ni0.1(CO3)(OH)2/GP and Co0.95Mn0.05CO3/GP compared to the commercial RuO2 electrocatalyst for oxygen evolution in alkaline media. It was also inferred that Co1.9Ni0.1(CO3)(OH)2/GP exhibited the best performance as indicated by the lowest overpotential (∼ 266 mV) in achieving 10 mA cm–2 current density, a small Tafel slope (∼ 44.8 mV dec–1), quite low charge-transfer resistance (∼ 0.72 Ω), and excellent durability. Thus, Ni-substituted Co2(CO3)(OH)2 nanostructures could be employed as promising, efficient, and durable electrocatalysts for the OER in alkaline media.