Ni/MoS2 Nanoparticles on Reduced Graphene Oxide for Gas-Phase Formic Acid Decomposition for the Production of Hydrogen

Abstract

The development of noble-metal-free nanomaterials for various applications is an important challenge. In this work, we propose a simple method for synthesizing Ni/MoS2/reduced graphene oxide (rGO) nanomaterials for gas-phase formic acid decomposition. In these catalysts, nickel atoms substitute for molybdenum atoms at the edges of MoS2 nanocrystals, and the rGO support ensures high dispersion of nanocrystals. These structural features are achieved by decomposing composite precursor-containing aerogels in Ar or NH3 flows at 873 K under thermal shock conditions. The resulting Ni/MoS2/rGO and N−Ni/MoS2/rGO catalysts are 3−7 times more active than the rGO-free Ni/MoS2 catalyst, which was also prepared by thermal shock. Accordingly, the apparent activation energies are lower (50 vs 78 kJ/mol). The conversion of formic acid over the developed catalysts is observed already at a temperature of about 373 K. It is important that the specific reaction rates are close to those of a Pd/C catalyst containing 2.3 nm Pd nanoparticles. DFT calculations showed that the presence of rGO in the system reduces the interaction energy of the formic acid molecule from 1.95 to 1.59 eV and facilitates the formation of the formate intermediate. The results of this work may allow to develop efficient MoS2/rGO-based systems for different catalytic applications.