Mechanism Investigation of Solvent Effect on Selective Decomposition of Formic Acid

The selective decomposition of formic acid to hydrogen gas represents a highly promising strategy for sustainable energy production. The influence of solvent effects on the selective decomposition of formic acid into H2 and CO2 or H2O and CO was investigated. A variety of solvents, including polar protic solvents (e.g., water, ethanol, methanol), polar aprotic solvents (e.g., tetrahydrofuran, dimethyl sulfoxide), and ionic liquids, were employed in conjunction with a 5 wt% Pd/C catalyst. The yield of formic acid decomposition and the turnover number (TON) were found to be dependent on the choice of solvent. To elucidate the solvent effects, classical solvent parameters and Kamlet–Taft solvatochromic parameters were studied. The study revealed correlations between the TON and the solubility of hydrogen, Kamlet–Taft parameters (acidity, basicity, and polarity/dipolarity), hydrogen bond donor (HBD) capability, and hydrogen bond acceptor (HBA) capacity. The solvent identity was found to play a dominant role in both the polarity/dipolarity and the catalytic mechanism of formic acid decomposition.