Abstract: Since the First Industrial Revolution, traditional fossil energy (coal, petroleum, etc.) has been the most important energy source. However, with social progress and technological development, energy consumption continues to increase. But fossil energy not only has limited reserves, it also causes serious problems (environmental pollution, the greenhouse effect). Therefore, the research and development of clean and sustainable energy are particularly important. One research focus is hydrogen energy. Hydrogen is a promising energy carrier due to its high energy density, clean-burning characteristics, and sustainability. However, the challenges of hydrogen storage and transportation seriously limit its practical application in proton exchange membrane fuel cells. A potential solution is hydrogen storage in the form of a more stable precursor. One such precursor, formic acid, decomposes easily at room temperature in the presence of a catalyst without also producing toxic gases. Effective catalysts for formic acid decomposition (FAD) are key to hydrogen production by this method. In this study, a high-performance palladium (Pd)-based catalyst boosted by thin-layered carbon nitride was prepared for formic acid decomposition. First, trimeric thiocyanate was calcined by a one-step method to obtain carbon nitride (C₃N₄-S) directly, followed by fabrication of a Pd-based FAD catalyst with C₃N₄-S as support (Pd/C₃N₄-S). During the pyrolysis of thiocyanuric acid, the overflow of-SH in the precursor had a peeling effect, so that the C₃N₄ formed as a thin, broken layer with a large specific surface area and pore volume. Because of the improved specific surface area and pore volume and the resulting large number of defect attachment sites, the C₃N₄-S support effectively dispersed Pd nanoparticles. Furthermore, owing to the electron effect between the support and the metal, the Pd²⁺ content on the catalyst surface could be adjusted effectively. Pd/C₃N₄-S showed excellent FAD performance. This catalyst decomposed formic acid into CO₂ and H₂ effectively at 30 ℃. The turnover frequency and mass activity were as high as 2083 h^-1 and 19.52 mol·g^-1·h^-1, respectively. Testing of the gas product by gas chromatography showed that it did not contain CO, indicating that the Pd/C₃N₄-S catalyst had excellent selectivity. The catalyst also had good stability:its performance decreased by less than 10% after four testing cycles. This study provides a guiding example of development of a formic acid hydrogen production catalyst with high cost performance and a simple preparation method.

Key words: Porous carbon nitride, Thin layer, Palladium nanoparticles, Heterogeneous catalysis, Formic acid dehydrogenation