Ruthenium-nickel-cobalt alloy nanoparticles embedded in hollow carbon microtubes as a bifunctional mosaic catalyst for overall water splitting.

The development of efficient bifunctional catalysts for both hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) is essential for reducing the cost of hydrogen production by water splitting. Herein, hollow microtubes composed of RuNiCo alloy nanoparticles uniformly embedded in the carbon matrix (RuNiCo@CMT) are prepared through a simple impregnation followed by reduction. Benefiting from the unique mosaic structure and the synergistic effect between Ru and NiCo, RuNiCo@CMT achieves more exposed active sites and improved reaction kinetics. As a consequence, RuNiCo@CMT exhibits considerable catalytic activities with the overpotentials of 78 mV for HER and 299 mV for OER at 10 mA cm in 1 M KOH. In addition, RuNiCo@CMT exhibits excellent stability for up to 30 h in both HER and OER processes at 20 mA cm, which is attributed to the protection of the RuNiCo alloy particles by the carbon layer. Furthermore, the assembled RuNiCo@CMT || RuNiCo@CMT overall water splitting system shows a cell voltage of 1.58 V at 10 mA cm. The density functional theory (DFT) calculations indicate that the addition of Ru can optimize the hydrogen adsorption free energy of Ni and Co sites. Finally, a solar panel-driven water splitting device is built, which can realize green and sustainable hydrogen production. The fabrication of RuNiCo@CMT provides a new way for the preparation of effective alloy nanomaterials for energy storage and conversion.