Full Spectrum Decomposition of Formic Acid over γ-Mo2N-Based Catalysts: From Dehydration to Dehydrogenation

Formic acid (FA) can be considered as CO and H2 carriers via the selective dehydration and dehydrogenation, respectively. Although various catalysts exhibit selective activity for FA decomposition, no active phase has been reported to be effective for both simultaneously. In this work, the FA decompositions over the bulk γ-Mo2N and the nitrogen-doped carbon (NC)-supported γ-Mo2N catalysts were investigated in detail. It is found that both catalysts showed obvious activity at low temperatures (100–200 °C). Interestingly, the reaction pathway was almost completely transformed from the selective dehydration over the bulk γ-Mo2N to the selective dehydrogenation over the NC-supported γ-Mo2N. Moreover, stable FA decomposition performances were observed with these two catalysts during the 45 h tests. The apparent transformation of the decomposition pathway could be ascribed to the acid–base properties of catalysts with different exposure facets. That is, the dehydration was favored by the acidic bulk γ-Mo2N with a preferential exposure facet of (111), whereas the dehydrogenation was benefited from the strong basic property of the NC-supported γ-Mo2N catalyst with the favorable exposed plane of (200).