Fabrication of a porous Pd film on nanoporous stainless steel using galvanic replacement as a novel electrocatalyst/electrode design for glycerol oxidation

• Nanopore arrays were formed on stainless steel surface substrate using anodization.
• Cu electrodeposited into the nanopores was spontaneously replaced with Pd.
• The electrode showed a remarkable catalytic activity for glycerol electrooxidation.
• Cu improves the reaction kinetics and increases the catalytic activity of the Pd.

In this work, nanoporous stainless steel (NPSS) prepared by anodization process was used as an electrode material to support noble metal-based catalysts. To decorate NPSS with Pd, copper was deposited into the pores of NPSS using pulsed electrodeposition, and followed by the galvanic replacement reaction between deposited Cu and PdCl2 solution. The surface morphology and composition of the prepared electrode were determined using scanning electron microscopy (SEM), atomic force microscopy (AFM) and energy dispersive X-ray spectroscopy (EDS). SEM and AFM images showed that self-organized nanopores with an average size of about 77 nm were formed on the stainless steel surface and then were successfully filled with Cu. Galvanic replacement resulted in the formation of a porous film with a high electrochemically active surface area (EASA = 173.4 cm2 mg−1) and greatly reducing Pd loading (29 μg cm−2). The EDS analysis revealed the presence of Cu and Pd in the prepared electrode (NPSS/Cu/Pd). Cyclic voltammetry, electrochemical impedance spectroscopy (EIS) and chronoamperometry techniques were used to investigate the electrochemical behavior of the NPSS/Cu/Pd electrode in alkaline media. It was found that the porosity of NPSS and the presence of Cu improve the long-term stability of the Pd film on the surface. The electrode exhibited a remarkable catalytic activity for electrooxidation of glycerol due to the large EASA. The obtained mass activity and onset potential for glycerol oxidation were 0.82 mA μgPd−1 and −0.35 V, respectively, which are acceptable as compared with those of palladium-carbon substrates. The results also indicated that the presence of Cu has a significant effect on the catalytic activity, the reaction kinetics and poisoning tolerance of the NPSS/Cu/Pd electrode. Accordingly, NPSS/Cu/Pd can be extended as a promising electrode for alcohol electrooxidation reactions in fuel cells and sensors.

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