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

Several palladium-based electrocatalysts dispersed onto a Vulcan XC-72 carbon support (Pd/C, PdxAu1−x/C and PdxPt1−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 (1.2–1.6 kWh(Nm3 H2)−1 compared to that necessary for water electrolysis (∼5 kWh(Nm3 H2)−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. 0.2–0.4 V at 100 mA cm−2.

► The thermodynamic characteristics of formic acid decomposition make this organic compound a convenient model molecule for PEMEC.
► Pd-based catalysts are active and stable for the anodic oxidation of formic acid.
► High reaction rates at relatively low overvoltages, i.e. 0.2–0.4 V at 100 mA cm−2, have been achieved in a PEMEC with platinum free Pd-based catalysts.
► More than two thirds of the electrical energy can be saved with formic acid decomposition in a PEMEC when compared to water.
► Performance degradation of Pd-based catalysts is partly due to CO-poisoning.