Synthesis of γ-Mo₂N/C catalysts and its performance on formic acid dehydrogenation

Formic acid (FA) has received much attention due to its high hydrogen content (4.4%), easy H₂ production and synthesis from small platform compounds. γ-Mo₂N/C is very selective for the decomposition of FA along the H₂ and CO₂ pathways, generating very little CO and showing high application value. In this study, γ-Mo₂N/C catalysts were prepared using aqueous p-phenylenediamine and ammonium molybdate solutions as precursors, and their FA decomposition performance was evaluated in-situ. The adsorption conformation of FA on the crystalline surface of γ-Mo₂N (200) was calculated by DFT, and on this basis, the catalyst performance and the decomposition mechanism of FA on its surface were investigated. The results showed that γ-Mo₂N/C exhibited very high catalytic activity at low temperatures and that improving the dispersion of γ-Mo₂N on the C carrier was effective in improving the FA conversion. The best catalytic performance was achieved at a molar ratio of 4∶1 between p-phenylenediamine and ammonium molybdate, and the catalyst showed stable performance and high H₂ selectivity (N₂ 40 mL/min, CO<5.0×10⁻⁵) in the FA decomposition experiments at 160 ℃ and 100 h. DFT calculations showed that the H atom of the O−H bond in FA was more likely to bind to the N atom on the crystalline surface of γ-Mo₂N/C (200), while the O atom of the C=O bond are more likely to bind to Mo atoms on the γ-Mo₂N/C (200) crystal plane. The above results help to clarify the mechanism of FA decomposition under the action of γ-Mo₂N/C and show the potential application of the non-precious metal catalyst γ-Mo₂N/C in the decomposition of FA for H₂ production.