Surface DBD plasma for preparation of highly active and stable Pd/O-NCNTs-P formic acid dehydrogenation catalysts in solution

Abstract The design and preparation of highly active and stable carbon materials-supported palladium catalysts is crucial for realizing hydrogen production from formic acid decomposition at low temperature and atmospheric pressure. In this work, a simple, environmentally friendly, and easily amplified surface dielectric barrier discharge (DBD) plasma was used to replace the toxic and harmful chemical reduction method to prepare oxygen-rich and amino-modified carbon nanotubes (CNTs) supported Pd catalyst (Pd/O-NCNTs-P) for formic acid dehydrogenation. The abundant oxygen-containing functional groups (OCGs) on the CNTs make it easy for amino modification. Both the OCGs and the -NH2 promote the formation of small-sized, highly dispersed Pd nanoparticles and enhance the metal-support interaction, which facilitate electron transfer and yields electron-deficient Pd2+. The charge repulsion among the Pd2+ species may further avoid the agglomeration of Pd species. The increase of the Pd2+/Pd0 ratio in the catalyst can regulate the electronic structure of Pd, thus promoting the formation and adsorption of formic acid dehydrogenation active intermediates (Pd-HCOO* and H*). Therefore, Pd/O-NCNTs-P showed excellent catalytic performance for formic acid dehydrogenation, with a turnover frequency (TOF) value of as high as 10888 h-1 for the first 120 s and a low activation energy Ea of 27.7 kJ·mol-1, and the activity remained unchanged even after six reaction cycles. This work provides a simple, green, and easy amplification method to prepare highly active and stable Pd catalysts for hydrogen production, which has great potential for practical application.