Co@Ir core-shell nanochain aerogels for the hydrogen evolution reaction and the oxygen evolution reaction in alkaline media

Developing efficient and stable oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) catalysts is critical for realizing large-scale hydrogen production via electrochemical water splitting. Here, we report a facile one-step over-reduction method to fabricate IrCo aerogels as efficient and durable HER and OER catalysts. Multiple characterization revealed that, IrCo aerogels possess a nano-chain-like structure composed of interconnected Co@Ir core-shell nanosphere particles. The as-prepared IrCo aerogels especially the Ir7Co3 sample showed excellent HER performance, evidenced by a small overpotential of 20.5 mV@10 mA cm-2 and a low Tafel slope of 28.87 mV dec-1 in 1.0 M KOH, which are significantly superior to those of a commercial benchmark Pt/C catalyst, and its OER performance is also better than that of a benchmark RuO2 catalyst, manifested by an overpotential of 269 mV@10 mA cm-2 and a Tafel slope of 31 mV dec-1. Moreover, in the overall water splitting (OWS) test, an applied voltage of 1.55 V was able to achieve a current density of 10 mA cm-2. Furthermore, the Ir7Co3 sample demonstrated remarkable long-term stability and was able to function continuously in the HER, OER, and OWS processes, maintaining a negligible change in current density of 10 mA cm-2 for 35, 37, and 44 hours, respectively. Such superior electrocatalytic properties of the Ir7Co3 aerogel are mainly attributed to the alloying effect and the structural features, which can increase the exposed metal active sites, improve the electrical conductivity, and facilitate the electron shuttling and mass transport during the electrocatalytic process. This study provides a facile and efficient generic approach for fabricating a metallic aerogel for the HER, OER, OWS and beyond. A facile one-step over-reduction method is developed to fabricate IrCo aerogels as efficient and durable HER and OER catalysts.