Fabrication Of Nanoporous Co₃O₄/Co Composite Film Electrodes And Their Electrocatalvtic Activities For OxygenEvolution Reaction

In the period of resource scarcity, hydrogen as environment-friendly and renewable energy is considered as the most promising alternative to fossil fuels. Oxygen evolution reaction (OER) works as the extremely significant half-cell reaction coupled with hydrogen evolution reaction (HER) in a water-splitting cell, an ideal method for efficiently generating hydrogen in high purity. The extra overpotential of OER has cut down the electric efficiency seriously, limiting this viable way to produce hydrogen in large scale. Conclusively, it is imperative to find a stable, effective and cheap catalyst to lower the reaction energy barrier and increase the electric eficiency.Although the noble metal-based catalysts exhibit the best overall electrocatalytic performance, the high cost and scarcity greatly hamper their practical widespread application. Transition metal compounds have attracted extensive attention due to their high catalytic activities, low cost and abundance on earth. Cobalt compounds with novel nanostructure have been recognized as a potential material because of their excellent catalytic activity. Herein we have successfully synthesized nanoporous Co films by a dealloying method. It is found that the inner diameter of cobalt pores can be effectively tuned by tailoring the concentration of Cu2+ in the electrodeposition solutions. When the concentration of Cu2+ is 0.05 M, the optimal nanoporous cobalt film is obtained, with a pore diameter of about 80-150 nm and a thickness of 0.8-1.3 μm.The nanoporous Co3O4/CO composite film electrode was further fabricated by the chemical oxidization and thermal treatment of as-prepared porous cobalt film. The nanoporous Co3O4/CO composite electrode shows an excellent catalytic ability and stability in the oxygen evolution reaction, with an onset OER overpotential of 250 mV. When current density is 10 mA cm-2, the overpotential of the nanoporous Co3O4/Co composite electrode is only 357 mV. While the overpotential of the controllable nanosheet Co3O4/Co electrode is 448 mV. The potential of the nanoporous Co3O4/Co composite electrode only increases about 3% after the electrolysis at the current density of 20 mA cm-2 for 48000 s. The excellent electrocatlytic activity and good stability for OER of the nanoporous Co3O4/CO composite electrode can be attributed to its unique nanoporous structure and highly reactive facets.