1. Laboratory of Advanced Power Sources, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022, China;2. University of Science and Technology of China, College of Applied Chemistry and Engineering, Hefei 230026, China;3. Jilin Province Key Laboratory of Low Carbon Chemical Power Sources, Changchun 130022, China;4. State Key Laboratory of Electroanalytical Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022, China
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.
