Palladium supported on carbon nitride sheets was developed to decompose formic acid under mild conditions. The obtained results revealed a clear structure–activity relationship between the Pd-exposed crystallographic planes and the catalytic performance. This study evidences the potential of these catalytic systems for effective application of formic acid as an energy vector.

Abstract

Carbon nitride, C₃N₄, was synthesized through thermal polycondensation of melamine with varying temperature and time conditions. This approach represents a cost-effective, straightforward, and environmentally friendly synthetic method with lower energy consumption to obtain hierarchically structured carbon nitride. The resulting materials were subjected to comprehensive characterization to analyze their crystalline structure, textural properties, composition, and light absorption characteristics. To evaluate their catalytic potential, the supports were impregnated with different loadings of palladium (1, 5, and 10 wt%) as the active phase and tested in the decomposition of formic acid for hydrogen production in liquid phase at mild conditions. This study revealed that the structure and composition of the C₃N₄ were highly dependent on the degree of polycondensation, which in turn was influenced by the temperature and the thermal synthesis process. The most promising catalytic performance was achieved with a support prepared by decomposing melamine at 650 °C for 4 h, followed by impregnation with 10 wt% Pd. Furthermore, a mechanistic study was conducted using operando DRIFTS-MS to explore the plausible catalytic pathways for synthesizing formic acid via CO₂ hydrogenation using the aforementioned catalyst. This investigation highlights the potential of C₃N₄ as a support, further demonstrating its versatility in the circular economy of formic acid.