Pt loading to promote hydrogen evolution from ammonia-borane hydrolysis of Ni2P under visible light

Abstract

Ammonia borane is a promising hydrogen storage material that can be handled easily and release hydrogen at room temperature in the presence of a catalyst. Attaching noble metal to transition metal phosphide is needed to improve the dehydrogenation from ammonia borane. Here, a catalyst Pt@Ni2P is reported to enhance the hydrogen evolution rate in dark and visible light. The incorporation of Pt with Ni2P exhibit partially positive Ptδ+ and partially negative Ni2Pδ− as manifested by X-ray photoelectron spectrum, which serve as active sites for ammonia borane and water, respectively. Moreover, visible light irradiation further accelerates the electron transfer from Ptδ+ to Ni2Pδ− as exhibited by electrochemical impedance spectroscopy and transient photocurrent spectra. Subsequently, Pt loading over Ni2P plays a vital role in improving H2 evolution rate via ammonia borane hydrolysis. With the incorporation of 2% Pt, the hydrogen generation rate from ammonia borane hydrolysis is increased by 4.0-fold in dark, and visible light irradiation further increases the activity by 5.7-fold compared with pristine Ni2P. The visible light enhances the turn-off frequency from 4.7 min−1 to 10.3 min−1 and reduces the activation energy from 52.0 kJ·mole−1 to 43.4 kJ·mole−1 compared with dark. The performance of Pt@Ni2P is also outstanding compared with reported catalysts and is expected to be used economically in practical applications.