The role of aluminium in metal–organic frameworks derived carbon doped with cobalt in electrocatalytic oxygen evolution reaction

Abstract

Water electrolysis is one of the most crucial processes in the development of new energy sources, where ultra-clean fuel is produced - hydrogen. Oxygen evolution reaction (OER) is the sluggish process of overall water splitting. Therefore, this study presents the design, characterization and electrochemical study of cobalt-based electrocatalysts embedded into porous carbons derived from an Al-metal–organic framework (MOF). The key aspects to be revealed were carbonization temperature and aluminium impact on the composite electrochemical performance. It was found that aluminium presence boosts the OER performance of the anode via lowering electrolyte resistance, reaching an overpotential of 380 mV at the current density of 10 mA/cm−2, which is improved by 80 mV compared to the composite without aluminium. Similar effect was present in EIS measurement, where the electrocatalyst functionalized with cobalt in the presence of aluminium showed the lowest resistances, 0.89 Ω and 2.82 Ω for R1 and R2. This is due to the formation of additional electrocatalytically active species in the form of Al-Co alloy what was clearly proved by the XPS study. It shows that cobalt favoured aluminium to act simultaneously as active sites accelerating the efficiency of the OER process. Additionally, carbon played the role of a booster of the OER activity of cobalt with sustained high durability during cycling. Therefore, a facile procedure to tune the structure of carbon-based structures derived from Al-based metal–organic frameworks is proposed and the resulting cobalt/aluminium modification serves as a robust electrocatalyst for OER.