Diffusion-restricted electrodeposition of platinum on solid carbon paste for electrocatalytic oxidation of methanol

• An attempt on diffusion restriction of ions for uniform electrodeposition.
• An additional 3D nucleation process in the initial deposition stage.
• Constant growth rate of Pt particles due to diffusion restriction.
• Equivalent circuit fitting for negative impedance and inductance.
• High catalytic activity to methanol oxidation kinetics.

Diffusion restriction of precursor ions was applied using filter paper during platinum electrodeposition on a solid carbon paste substrate, in order to uniformize the growth of Pt catalyst particles. An additional 3D nucleation process was then observed in the initial deposition stage, and the growth rate of Pt particles kept constant over whole deposition time. The prepared particles showed a sunflower-head-like morphology with numerous nanoscale “seeds” on the surface. Both the “sunflower-heads” and the “seeds” become more uniform in size, shape and surface distribution due to diffusion restriction, leading to an increase in the electrochemical active area of Pt particles and an enhancement in methanol oxidation kinetics. The analysis of electrochemical impedance spectroscopy by equivalent circuit fitting yields potential-dependent charge-transfer resistances and inductances with the same sign (positive or negative), corresponding to the regeneration or passivation of surface active sites at different potentials. This study offers insight into the role of the diffusion-restricted electrodeposition in preparing the catalyst particles with high catalytic activity.

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