Potential–Rate Correlations of Supported Palladium-Based Catalysts for Aqueous Formic Acid Dehydrogenation

Abstract

Aqueous formic acid dehydrogenation (FAD) is a crucial process for hydrogen production, as hydrogen is a clean energy carrier. During this process, formic acid converts into hydrogen and carbon dioxide over a catalyst. Pd-based catalysts have exhibited significant potential in FAD due to their high activity and selectivity. In this study, we investigated aqueous thermal FAD in a mixture of formic acid and sodium formate using electrochemical open-circuit potential (OCP) measurement by loading the catalysts onto a conductive substrate as a working electrode. By varying the reaction conditions such as the concentration of reactants and modifying Pd with Ag, different FAD rates were obtained. Consequently, we revealed the correlation between the catalyst OCP and FAD rate; superior FAD rates reflected a more negative catalyst OCP. Furthermore, deactivation was observed across all catalysts during FAD, with a concurrent increase in catalyst OCP. Interestingly, we found that the logarithm of the FAD rate showed a linear correlation with the OCP of the catalyst during the decay phase, which we quantitatively explained based on the reaction mechanism. This study presents a new discovery that bridges thermal and electrocatalysis.