Abstract
Nickel (oxy)hydroxides (NiOxHy) are promising cost-effective materials that exhibit a fair catalytic activity for the ethanol oxidation reaction (EOR) and could be used for sustainable energy conversion. Doping the NiOxHy structure with other metals could lead to enhanced catalytic properties but more research needs to be done to understand the role of the doping metal on the EOR. We prepared NiOxHy films doped with Fe or Co with different metallic ratios by electrodeposition and evaluated the EOR. We found a positive and negative effect on the catalytic activity after the incorporation of Co and Fe, respectively. Our results suggest that Ni atoms are the active sites for the EOR since Tafel slopes were similar on the binary and pristine nickel (oxy)hydroxides and that the formal potential of the Ni(II)/Ni(III) redox couple is a good descriptor for the EOR activity. This work also highlights the importance of controlled metal doping on catalysts and may help in the design and development of improved materials for the EOR.Graphical Ethanol oxidation reaction was studied on different electrodeposited nickel (oxy)hydroxides modified with iron or cobalt. Enhanced activity was observed for the materials modified with cobalt, while iron doping had a negative influence. Results also suggest that nickel atoms are the active sites in the bimetallic materials.
Highlights
In the last years, much effort has gone into the study of the electrochemical oxidation of alcohols for energy-related applications such as fuel cells [1] or hydrogen generation [2]
We evaluated Nihydroxide films with the incorporation of increasing amounts of Fe or Co for the ethanol oxidation reaction (EOR)
Co doping led to enhanced EOR catalysis while Fe addition showed a negative effect
Summary
Much effort has gone into the study of the electrochemical oxidation of alcohols for energy-related applications such as fuel cells [1] or hydrogen generation [2]. Especially Pt or Pd, show high electrocatalytic activity towards alcohol oxidation at low potentials. These materials have several drawbacks, such as limited global availability, high cost and deactivation issues by irreversible. Carbon nanofibers modified with NiCo alloyed nanoparticles showed increased catalytic activity for ethanol oxidation [16] compared to the same material formed only by nickel nanoparticles. These alloyed nanoparticles were synthesized at high temperatures in a reducing atmosphere leading to elemental NiCo, which needed electrochemical activation to generate active nickel hydroxides for ethanol oxidation. Materials with different geometric structures such as mesoporous NiCo2O4 fibers showed enhanced activity compared to NiO and Co3O4 materials [19], demonstrating the positive synergistic effect of combining both materials
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