Tuning carbon nanotube-grafted core-shell-structured cobalt selenide@carbon hybrids for efficient oxygen evolution reaction.

The electrochemical oxygen evolution reaction (OER) is sparked extensive interest in efficient energy storage and conversion. Cobalt Selenide (CoSe) is believed to be one of the promising candidates for OER based on Yang Shao-Horn's principle. However, owing to low exposure of active sites and/or low efficiency of electron transfer, the electrocatalytic activity of CoSe is far less than expected. In this work, a novel carbon nanotubes (CNT) grafted 3D core-shell structured CoSe@C-CNT nanohybrid is developed by a general hydrothermal-calcination strategy. Zeolite imidazole frameworks (ZIF) was used as the precursor to synthesis of the materials. It is found that both the calcination temperature and the selenium content can significantly regulate the catalytic performance of the hybrids. The obtained best catalysts requires the overpotential of only 306 mV and 345 mV to reach a current density of 10 mA cm and 50 mA cm in 1.0 MKOH medium, respectively. It also exhibits a small Tafel slope of 46 mV dec and excellent durability, which is superior to most of recently reported CoSe-based and Co-based materials. These superior performances can be ascribed to synergistic effects of the highly active CoSe nanostructure, defect carbon species and the carbon nanotubes exist in the catalyst. Besides, the unique morphology leads to large electrochemical surface area of the catalyst, which is in favor of the exposure of active sites for OER. Due to high efficiency, low cost and excellent durability for OER, the prepared catalysts showed can be potentially used to substitute noble metals utilized in related energy storage and conversion devices.