Porous Carbon/rGO Composite: An Ideal Support Material of Highly Efficient Palladium Electrocatalysts for the Formic Acid Oxidation Reaction

Catalyst support materials play an important role in the electrochemical performance of the catalyst in fuel cells. Herein, we present a synergistic effect of surface area and electronic conductivity on the efficiency of a carbon support material towards its application in direct formic acid fuel cells. A composite of reduced graphene oxide (rGO) and metal organic framework (MOF-5) derived porous carbon (PC) was used as a novel support material for a high dispersion of palladium nanoparticles. The rGO₁-C₁ electrocatalyst, which consists of an equal ratio of PC and rGO, was found to be the most effective for the formic acid electro-oxidation reaction. The obtained mass specific activity for Pd/rGO₁-C₁ (969.76 mA mg⁻¹) is 1.52 times higher than for Pd/rGO (639.5 mA mg⁻¹) and 2.63 times higher than Pd/C (368.73 mA mg⁻¹) synthesized under the same conditions and at given onset peak potentials. The Pd/rGO₁-C₁ electrocatalyst was also found to be much more stable than other catalysts as evidenced by chronoamperometric measurements for up to 3000 s. The high activity and stability of the catalyst fabricated over the composite carbon support is due to a synergism between the Pd metal and the composite support toward charge transfer, where highly porous carbon provides a high surface area and the rGO is highly conductive, thereby boosting the electrical properties of the catalyst.