Catalyzed Hydrolysis of Tetrahydroxydiboron by Graphene Quantum Dot-Stabilized Transition-Metal Nanoparticles for Hydrogen Evolution

Abstract

The search of new H2 evolution systems avoiding fossil sources and their mechanisms is a priority in the 21st century society. Hydrolysis of tetrahydroxydiboron (TDB), a current borylation source in the literature, is used here for H2 evolution for the first time. It is catalyzed by graphene quantum dot-stabilized nanoparticles (NPs). With RhNP- or PtNP-catalyzed reactions, D2 formation from D2O confirms that water is the only hydrogen source. Kinetic isotopic effects yield kH/kD = 5.91 and 4.18, strongly suggesting double water O–H bond cleavage on the NP surface in the rate-limiting step. The most efficient catalysts are the RhNP and PtNP (total turnover frequencies: 3658 and 4603 molH2·molcat–1·min–1, respectively). The order of catalytic activity is as follows: PtNP > RhNP > AuNP > PdNP > IrNP > RuNP, and a catalytic mechanism of TDB hydrolysis is proposed.