Evidence of surface restructuration on Pt–Rh/C and Pt–Rh–Ni/C nanoparticles applied to ethanol electrooxidation reaction

Enhancing Ethanol Electrooxidation in Acidic Media Using Pt Nanoparticles Supported on Metal Oxide-Modified Vulcan XC72 Nanocomposites

Nanocomposite electrode materials based on Pt nanoparticles (Pt NPs) deposited on various carbonaceous materials (Carbon Black-Vulcan XC72, graphene, and graphite) were fabricated and evaluated for ethanol electrooxidation reaction (EOR) in acidic media. The promotional effects of calcination and incorporation of metal oxides (TiO2, SnO2, ZnO, Fe2NiO4, Fe2O3, CuFe2O4, ZnFe2O4, and 5% Ru on alumina) into Vulcan XC-72 on the performance of Pt NPs toward EOR were systematically evaluated. Pt NPs (∼20 wt %) were synthesized via a facile NaBH4 reduction method at ambient temperature, yielding spherical nanoparticles with minimal agglomeration. Physicochemical characterization (XRD, TEM, and SEM) confirmed uniform Pt dispersion and reduced particle size on calcined Fe2O3-C supports. Electrochemical analysis (CV, CA, LSV, and EIS) revealed that calcined Pt/5% Fe2O3-C exhibited superior EOR activity, with a low onset potential (0.2 V vs Ag/AgCl), high current density (0.52 mA/cm2), and enhanced stability (retaining >34% activity after 3000 s). Dual calcination (pre/post-Pt deposition) stabilized ultrasmall Pt NPs (3.09 nm) on Fe2O3-C, achieving 2.3 times higher mass activity than Pt/C. The improved performance is attributed to synergistic electronic effects, optimized Pt-support interactions, and Fe2O3-mediated C-C bond cleavage. This work highlights the efficacy of dual thermal annealing (pre- and post-Pt deposition) in stabilizing Pt NPs and advancing DEFC catalyst design.

Catalyst Development for High-Temperature Polymer Electrolyte Membrane Fuel Cell (HT-PEMFC) Applications

A constant increase in global emission standard is causing fuel cell (FC) technology to gain importance. Over the last two decades, a great deal of research has been focused on developing more active catalysts to boost the performance of high-temperature polymer electrolyte membrane fuel cells (HT-PEMFC), as well as their durability. Due to material degradation at high-temperature conditions, catalyst design becomes challenging. Two main approaches are suggested: (i) alloying platinum (Pt) with low-cost transition metals to reduce Pt usage, and (ii) developing novel catalyst support that anchor metal particles more efficiently while inhibiting corrosion phenomena. In this comprehensive review, the most recent platinum group metal (PGM) and platinum group metal free (PGM-free) catalyst development is detailed, as well as the development of alternative carbon (C) supports for HT-PEMFCs.

Unexpected Negative Performance of PdRhNi Electrocatalysts toward Ethanol Oxidation Reaction

Direct ethanol fuel cells (DEFCs) need newly designed novel affordable catalysts for commercialization. Additionally, unlike bimetallic systems, trimetallic catalytic systems are not extensively investigated in terms of their catalytic potential toward redox reactions in fuel cells. Furthermore, the Rh potential to break the ethanol rigid C-C bond at low applied potentials, and therefore enhance the DEFC efficiency and CO₂ yield, is controversial amongst researchers. In this work, two PdRhNi/C, Pd/C, Rh/C and Ni/C electrocatalysts are synthesized via a one-step impregnation process at ambient pressure and temperature. The catalysts are then applied for ethanol electrooxidation reaction (EOR). Electrochemical evaluation is performed using cyclic voltammetry (CV) and chronoamperometry (CA). Physiochemical characterization is pursued using X-ray diffraction (XRD), transmission electron microscope (TEM), energy-dispersive X-ray spectroscopy (EDX) and X-ray photoelectron spectroscopy (XPS). Unlike Pd/C, the prepared Rh/C and Ni/C do not show any activity for (EOR). The followed protocol produces alloyed dispersed PdRhNi nanoparticles of 3 nm in size. However, the PdRhNi/C samples underperform the monometallic Pd/C, even though the Ni or Rh individual addition to it enhances its activity, as reported in the literature herein. The exact reasons for the low PdRhNi performance are not fully understood. However, a reasonable reference can be given about the lower Pd surface coverage on both PdRhNi samples according to the XPS and EDX results. Furthermore, adding both Rh and Ni to Pd exercises compressive strain on the Pd lattice, noted by the PdRhNi XRD peak shift to higher angles.

Rhodium effects on Pt anode materials in a direct alkaline ethanol fuel cell

The development of efficient catalysts for ethanol oxidation in alkaline medium requires a synthetic approach that may prevent the surfactant molecules from being adsorbed at the catalytic sites and decreasing the electrochemical performance of the final direct ethanol fuel cell. Toward this goal, the recently reported surfactant-less Bromide Anion Exchange (BAE) method, appears as a promising route to conveniently aim at preparing PtRh alloys dispersed on carbon substrates. The catalysts prepared herein by the BAE method were characterized physicochemically to obtain structural information on the PtRh/C nanomaterials, their morphology (size and shape), and their chemical and surface composition. Electrochemical behavior and properties of these electrodes were then investigated in a half-cell before the implementation of a direct ethanol fuel cell (DEFC) in a home-made anion exchange membrane Teflon cell. The analysis of the electrolytic solution in the anodic compartment by chromatography revealed that acetate was the major reaction product and the carbonate amount increased with the Rh content in the bimetallic composition. With 2.8–3.6 nm particle sizes, the Pt₅₀Rh₅₀/C catalyst exhibited the highest activity towards the ethanol electrooxidation.

The development of efficient catalysts for ethanol oxidation in alkaline medium requires an approach that avoids surfactant molecules from being adsorbed at active sites and decreasing the electrochemical performance of the direct ethanol fuel cell.