Temperature-Dependent Electrocatalytic Methanol Oxidation Over a Pd/MnO2/Exfoliated Boron Ternary Composite in an Alkaline Medium

The development of efficient and durable electrocatalysts for the methanol oxidation reaction (MOR) is crucial for advancing alkaline direct methanol fuel cells. Herein, a Pd/MnO 2 /exfoliated boron (Pd/MnO₂/eB) ternary composite was synthesized via solvent-assisted boron exfoliation, hydrothermal growth of MnO₂, and ultrasonic integration of Pd nanoparticles. Structural characterization indicates the successful formation of crystalline MnO 2 decorated with Pd nanoparticles on eB sheet. The ternary composite exhibited higher electrocatalytic activity toward MOR in 2 M NaOH containing 2 M methanol, achieving a maximum forward oxidation current density of 4.5 mA mg − 1 Pd as compared to Pd/C (2.75 mA mg − 1 Pd). The temperature-dependent studies of Pd/MnO 2 /eB revealed that increasing temperature enhanced methanol oxidation by promoting reactant diffusion, hydroxide-ion transport, and electron-transfer kinetics, with optimum performance achieved at 323 K. Arrhenius analysis yielded an apparent activation energy of 47.9 kJ mol − 1 , while Eyring analysis gave an activation enthalpy of 45.5 kJ mol − 1 , an activation entropy of -113 J mol − 1 K − 1 , and activation Gibbs free energies of 79.8–83.2 kJ mol − 1 , indicating that methanol oxidation proceeds through the formation of a ordered activated complex with a moderate energy barrier. A plausible mechanism is proposed in which Pd catalyses methanol adsorption and dehydrogenation, MnO 2 supplies reactive hydroxyl species for oxidative removal of poisoning intermediates, and exfoliated boron enhances electron transport.