Promoting Effect of Co(OH)₂ for Supported Pt Nanocatalysts toward Catalytic Hydrolysis of Ammonia Borane

Catalytic hydrolysis of ammonia borane for dehydrogenation is a promising way for generation and storage of hydrogen energy. Catalysts with reduced utilization of costly noble metals while high activity and stability are highly desired. Herein we show that the catalytic activity of the prototypical Pt/SiO₂ catalysts towards ammonia borane hydrolysis could be significantly improved by the presence of a layer of Co(OH)₂ beneath the supported Pt nanoparticles. By changing the Pt: Co molar ratio in the Pt-Co(OH)₂/SiO₂ catalysts, the hydrogen generation rates from ammonia borane hydrolysis show a volcano-type curve, with the maximum catalytic activity at the Pt: Co molar ratio of 1:11. The highest turnover frequency value of 829 mol_H2·mol_Pt^-1·min^-1 at room temperature outperforms most of the reported Pt-based catalysts, and the apparent activation energy is drastically decreased to 36.2 kJ/mol from 61.6 kJ/mol for Pt/SiO₂. The enhanced catalytic performance of Pt-Co(OH)₂/SiO₂ is attributed to the electrons donation from Co atoms on Co(OH)₂ to Pt occurring at the metal-hydroxide interface, which is beneficial for optimizing the oxidation cleavage of the O-H bond of attacked H₂O.