Engineering PdCo bimetallic catalysts on multi-walled carbon nanotubes via Pd/Co ratio regulation for enhanced electrocatalytic ethanol oxidation: Synergistic effect and electronic structure optimization

In this study, a series of Pd Co bimetallic catalysts (Pd1Co1/C, Pd1Co2/C, Pd1Co5/C) were designed and prepared using multi-walled carbon nanotubes (MWCNTs) as supports, leveraging the strong reducing effect of sodium borohydride (NaBH 4 ) and bimetallic synergistic interactions. The objective was to optimize the electrocatalytic ethanol oxidation performance by tuning the Pd/Co ratio, with a target metal loading of approximately 0.3 mg/cm 2 . Experimental results show that the introduction of Co modulates the d-band center of Pd through electronic effects, weakening the strong adsorption of intermediates (such as Co-like species and acetaldehyde), while the high electrical conductivity and specific surface area of MWCNTs significantly enhance the dispersion of active sites and electron transfer efficiency. Electrochemical tests indicate that Pd1Co2/C exhibits the optimal catalytic activity, with a Tafel slope as low as 24.15 mV dec −1 , an exchange current density of 4430 mA/g, a specific capacitance (Cs) of 4.3 mF/cm 2 , and an electrochemical active surface area of 6.58m 2 /g. This is attributed to the synergistic promotion of reaction kinetics by the Pd Co alloy structure and the stabilizing effect of the support on nanoparticles. XRD and TEM characterizations further confirm the interatomic interactions of the bimetallic system and uniform loading characteristics. This work investigates the influence of Pd/Co ratio adjustment on the electrocatalytic ethanol oxidation performance of bimetallic catalysts, revealing the critical role of the bimetallic ratio in optimizing reaction kinetics and intermediate adsorption behavior. The findings provide experimental insights for the design of efficient anode catalysts for direct ethanol fuel cells (DEFCs).