Theoretical insight into the role of nitrogen in the formic acid decomposition over Pt13/N-GNS

Highlights: • DFT calculation was used to study of role of N dopant in HCOOH decomposition. • Nitrogen dopant in carbon support can tune the catalytic process by two effects. • Ligand effect from nitrogen tunes the electronic properties of metal active center. • Catalytic effect from nitrogen site can efficiently capture hydrogen atom. • Microkinetic simulations unravels the optimal nitrogen doping concentration. Catalytic decomposition of formic acid is regarded as one of the most promising hydrogen source conversion technologies. Nitrogen doped carbon supported metal catalyst emerges in recent years and delivers excellent performance in formic acid hydrogenation. However, there is not a well-recognized explanation about the real role of the nitrogen dopant in carbon support. In this work, density functional theory-based calculations were used to individually study the ligand effect and catalytic effect from the nitrogen dopant. Ligand effect mainly tunes the electronic properties of metal active center by shifting d-band center far away from Fermi level. The result unravels that CH scission path is more favorable compared with OH scission path. Catalytic effect is originated from the lower electrostatic potential of nitrogen active site compared with platinum, making N site an efficient capturer for hydrogen atom. Though activation energy for cleaving OH bond is higher than CH bond, nitrogen site can efficiently cleave the OH bond. Microkinetic simulations are performed to obtain the best nitrogen doping concentration in the carbon support. It implies that the optimal nitrogen concentration is a function of temperature, according to the optimized curve. This work will improve the understanding of mechanism of formic acid decomposition and provide new method in modifying metal/carbon support catalysts.