Nickel metaphosphate supported ruthenium for all pH hydrogen evolution: From single atom, cluster to nanoparticle

Single-atom catalysts have attracted extensive attention due to their unique performances and high atom utilization. However, is single atom always the best? Here we found a reverse case that nickel metaphosphate (NPO) supported nanoparticles (Run) is much better than single atoms (Rus) for all pH hydrogen evolution. The mass activity of Run-NPO is 3.8 times higher than that of Rus-NPO, and 21.4 times higher than that of Pt/C in alkaline media. The results show that Ru nanoparticle possess lower valence state than single atom, providing optimized Ru-H bond strength and suitable hydrogen adsorption free energy. As a novel support, NPO is also essential for firmly anchoring Ru and transporting electrons for optimizing the d-band center, and eventually accelerating the H2O dissociation in rate-limiting Volmer step. This work gives Ru-NPO promising potential for practical hydrogen production, and sheds light on the exploration of supported metal catalysts in energy conversion-related fields.