Clean hydrogen generation through the electrocatalytic oxidation of formic acid in a Proton Exchange Membrane Electrolysis Cell (PEMEC)

摘要

Several palladium-based electrocatalysts dispersed onto a Vulcan XC-72 carbon support (Pd/C, Pd_xAu_(1-x)/C and Pd_xPt_(1-x)/C) were prepared by the "water-in-oil" microemulsion method and characterized by physicochemical methods (TEM, HRTEM, EDX, XRD, etc.). The electrochemical activity of these catalysts towards the electro-oxidation of formic acid was investigated by cyclic voltammetry, and compared to that obtained with the monometallic catalysts. The electrochemical decomposition of formic acid in a PEMEC at relatively low cell voltages (0.2-0.7 V for a current density of 100 mA cm~(-2) according to the catalyst used) was performed with a much lower electrical energy (1.2-1.6kWh(Nm~3 H_2)~(-1) compared to that necessary for water electrolysis (～5 kWh(Nm~3 H_2)~(-1). Formic acid has been chosen as a model compound with the lowest decomposition energy (ΔH ～ 32 kJ mole~(-1)) compared to that needed for water decomposition (ΔH ～ 286 kJ mole~(-1)). It has been demonstrated that this technology may allow saving at least two thirds of the electrical energy needed by the classical water electrolysis technology for producing pure hydrogen. Moreover the use of platinum free Pd-based catalysts for the anodic oxidation of formic acid leads to high reaction rates at relatively lower overvoltages, i.e. 0.2-0.4V at 100 mA cm~(-2).