Mechanistic insights into hydrogen production from formic acid catalyzed by Pd@N-doped graphene: The role of the nitrogen dopant
Preeyaporn Poldorn, Yutthana Wongnongwa, Ruiqin Zhang, Sarana Nutanong, Lin Tao, Thanyada Rungrotmongkol, Siriporn Jungsuttiwong
Abstract
The catalytic decomposition of formic acid (HCOOH) is a crucial process for hydrogen production technologies. Herein, periodic density functional theory (DFT) calculations were employed to explore the effect of N-doping on the decomposition of formic acid. We designed a series of single Pd-atoms deposited in the single vacancy of N-doped graphene sheets , namely Pd-DGr, Pd–N1Gr, Pd–N2Gr, and Pd–N3Gr, as the proposed catalysts. Our findings show that H 2 production from HCOOH dehydrogenation on these surfaces proceeds via the formate (HCOO) pathway ( Path-I ) rather than the carboxylate (COOH) pathway ( Path-II ). Furthermore, the Pd–N3Gr catalyst shows the greatest catalytic reactivity toward HCOOH dehydrogenation via Path-I , requiring an activation energy (E a ) of 0.38 eV. On the other hand, the undesirable dehydration of HCOOH to carbon monoxide (CO) through COOH ( Path-IIIA ) or formyl (HCO) ( Path-IIIB ) intermediates is unlikely to occur on Pd–N3Gr due to a large activation energy . We found that the active species on the catalyst surface increased with N-doping concentration. Additionally, microkinetic simulations of the HCOOH decomposition on these surfaces confirmed the high activity and selectivity of the Pd–N3Gr catalyst toward HCOOH dehydrogenation ( Path-I ). These calculated results highlight that the Pd–N3Gr catalyst is a promising candidate for the formic acid decomposition reaction to yield hydrogen.