Engineered Modular Design of a Nanoscale CoNP/Au_nano Hybrid Assembly for High-Performance Overall Water Splitting

For water-splitting catalysis, the activity and performance of transition-metal-based catalysts can be accelerated by modular designing of the system with a hybrid combination. Here, a unique, nanofunctional three-dimensional (3D) substrate–catalyst hybrid assembly with mutually related high conductivity, improved electronic structure, flexibility, and redox behavior, and a plethora of surface-active sites is developed, resulting in remarkable oxygen evolution reaction (OER)/hydrogen evolution reaction (HER) activity from a simple and single catalytic platform. The hybrid and synergistic combination of controlled electrodeposited CoNPs on 3D Aunano substrates reveals unprecedented water-splitting activity with very promising kinetics and sustained stability for a prolonged period. The engineered CoNPs/Aunano hybrid assembly exceedingly surpasses the activity of CoNPs on other substrates, Co3O4 NPs and IrO2. The onset potential for water oxidation is E/V = 1.43 VRHE (η = 200 mV), which is extremely low and comparable to that of IrO2. With a low Tafel slope of just 52 mV dec–1, the CoNPs/Aunano hybrid assembly presents remarkable stability for 180 continuous hours of electrolysis. The noteworthy enhancement in overall activity is ascribed to the unique nanoscale-level collaborations in the CoNPs/Aunano hybrid assembly, demonstrating enhanced electronic transport for overall water splitting. CoNPs/Aunano also exhibit remarkable HER activity and full water-splitting performance in the two-electrode system. No obvious change in the catalyst structure and morphological attributes are observed during characterization studies after OER.