Hydrolysis of ammonia borane for green hydrogen production over a Pd/C3N4 nanocatalyst synthesized by electron beam irradiation†

Abstract

Ammonia borane (AB), which possesses a theoretical hydrogen storage capacity of 19.6 wt%, is extensively examined to tackle solid state hydrogen storage challenges. In this paper, we present a strategy to synthesize Pd dispersed g-C₃N₄ by decorating different concentrations of Pd on the g-C₃N₄ matrix by electron beam irradiation process. Catalyst characterization reveals successful formation of g-C₃N₄ supported highly dispersed face-centred cubic nanocrystalline Pd, with a particle size of less than 10 nm. The catalyst performance for AB hydrolysis exhibits an activation energy of 27.36 kJ mol⁻¹, surpassing many Pd-based catalysts. Successive hydrolysis experiments and detailed analysis of the spent catalyst establish the reusability and stability of the catalyst. The study shows that though the initial AB concentration does not affect the hydrolysis reaction rate, addition of impurity ions to the reaction media can significantly modify it. Detailed mechanistic investigation by the kinetic isotope effect, time dependent FT-IR, and mass spectrometry clarifies that the evolved hydrogen from the AB hydrolysis reaction comes from both the breakage of the B–H bond and hydrogen from the solvent. Activation of the O–H bond of the solvent due to the adsorption on the catalyst surface plays a significant role in the AB hydrolysis reaction and comprises the rate-determining step.