Pd Nanoparticles Supported on Carbon Nanotubes with Carbonyl-Driven Pd⁰–Pd^δ+ Interface Formation for the Catalytic Dehydrogenation of Formic Acid

Formic acid, renowned as an exceptional hydrogen storage candidate, has garnered significant attention. However, its widespread application in the hydrogen economy is impeded by the low activity and inadequate stability of dehydrogenation catalysts. In this paper, the activity and stability of Pd-based catalysts for formic acid hydrogen release were enhanced through the regulation of the variety of oxygen-containing functional groups on the surface of carbon nanotubes (CNTs) via high-temperature alkali etching. A comprehensive series of characterizations and experimental results demonstrated that high-temperature alkali etching significantly enhances the proportion of carbonyl CO in the oxygen-containing functional groups. This amplifies the dispersion of Pd nanoparticles and simultaneously modulates the electronic structure of the Pd nanoparticles. The transfer of electrons from Pd to carbonyl CO facilitates the generation of positively charged Pd^δ+ nanoparticles, thereby reducing the activation energy required for formic acid dehydrogenation. Density functional theory (DFT) calculations further revealed that the carbonyl group augments the electron concentration at the interface between the Pd cluster and the support. These findings bear substantial implications for the design of high-performance catalysts for formic acid dehydrogenation.