Formic acid-ammonium formate mixture: A new system with extremely high dehydrogenation activity and capacity

摘要

Formic acid (FA) ammonium formate (AF) mixture is studied as a possible new system for dehydrogenation over a common Pd/C catalyst synthesized via a modified impregnation-NaBH4 reduction method. The composition and morphology of the Pd/C catalyst are characterized using X-ray diffraction, energy-dispersive X-ray spectroscopy, transmission electron microscopy, high-resolution transmission electron microscopy, and inductively coupled plasma atomic emission spectrometry. Results show that the initial turn-over frequency of the FA AF mixtures with total FA and AF concentration of 10 mol dm(-3) and FA molar fraction of 0.2 can reach 7959 h(-1) at 50 degrees C, which is the highest value reported for heterogeneous Pd-based catalysts in FA-based systems. FA in this mixture can completely decompose and deliver an electrochemical capacity of 565.87 mAh mL(-1). The activity and stability of the Pd/C catalyst in this system are greatly improved in comparison with those of FA sodium formate system. The excellent dehydrogenation performance of FA AF mixture can be attributed to the catalytic activity of formate toward the decomposition of FA, the effect of ammonia adsorption on Pd/C catalyst, and the higher solubility of AF in FA solution. (C) 2016 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.