Anion exchange membrane fuel cells (AEMFCs) offer several important advantages with respect to proton exchange membrane fuel cells, including the possibility of avoiding the use of platinum catalysts to help overcome the high cost of fuel cell systems. Despite such potential benefits, the slow kinetics of the hydrogen oxidation reaction (HOR) in alkaline media and limitations in performance stability (because of the degradation of the anion conducting polymer electrolyte components) have generally impeded AEMFC development. Replacing Pt with an active but more sustainable HOR catalyst is a key objective. Herein, we report the synthesis of a Pd−CeO 2 /C catalyst with engineered Pd-to-CeO 2 interfacial contact. The optimized Pd−CeO 2 interfacial contact affords an increased HOR activity leading to >1.4 W cm −2 peak power densities in AEMFC tests. This is the only Pt-free HOR catalyst yet reported that matches state-of-the-art AEMFC power performances (>1 W cm −2 ). Density functional theory calculations suggest that the exceptional HOR activity is attributable to a weakening of the hydrogen binding energy through the interaction of Pd atoms with the oxygen atoms of CeO 2 . This interaction is facilitated by a structure that consists of oxidized Pd atoms coordinated by four CeO 2 oxygen atoms, confirmed by X-ray absorption spectroscopy.

Electroreforming is a low energy cost technology that combines the production of valuable chemicals from biomass-derived alcohols with the evolution of clean hydrogen at low temperature and atmospheric pressure. The selectivity for the desired chemicals is governed by the nature of the anode catalyst. Here we report the synthesis and characterization of a carbon supported nanostructured Rh electrocatalyst. The Rh nanoparticles are shown to be highly dispersed (2.2 nm) and a complete electrochemical study is reported. This Rh/C catalyst exhibits high activity for alcohol electrooxidation (e.g. 5700 A gRhfor EG at 80 °C) and when employed with an anion exchange membrane and Pt/C cathode in an electroreformer produces high volumes of hydrogen at low electrical energy input (e.g. 500 mA cmâ\u88\u922at 0.7 Vcelland Ecost= 9.6 kW h kgH2â\u88\u921). A complete analysis of the alcohol oxidation products from several renewable alcohols (ethanol, ethylene glycol, glycerol and 1,2-propandiol) shows a selectivity in the formation of valuable chemicals such as lactate and glycolate

Nicked-based metal−organic framework-derived carbon (Ni/MOFDC) and its acid-treated counterpart (AT-Ni/ MOFDC) have been prepared as supports for palladium nanoparticle electrocatalysts (Pd/Ni/MOFDC and Pd/AT-Ni/MOFDC). These materials have been prepared using facile microwave-assisted techniques. Several spectroscopic and microscopic techniques (such as FTIR, Raman, PXRD, XPS, XANES, FT-EXAFS, and TEM) have been used to thoroughly characterize physicochemical properties of the materials. It is revealed that acid treatment successfully cleaned the metallic Ni surface of the passivating hydroxides (Ni(OH) 2 and NiOOH) to generate a very low concentration of Ni nanoparticles on the carbon support. The Ni-deficient Pd/AT-Ni/MOFDC shows excellent electrocatalytic performance toward ethanol oxidation reaction (EOR) in the alkaline medium compared to the Ni-hydroxide-rich Pd/Ni/MOFDC counterpart.As a proof-of-concept, these electrocatalysts have been employed as anodes and demonstrated for membraneless direct ethanol microfuel cells (μ-DEFCs) with a micro-3D-printed cell, with FeCo/C as electrocatalyst for the oxygen reduction reaction at the cathode. The Pd/AT-Ni/MOFDC displays increased peak power density (P m = 26.49 mW cm −2 ) with 68% voltage retention after a 24 h galvanostatic discharge test at 40 mA cm −2 and reduced impedance. The improved electrocatalytic properties of the Pd/AT-Ni/MOFDC underscore the need to clean the nickel surface of its passivating hydroxides to harness its full promotional activities toward alcohol oxidation reaction on precious metal electrocatalysts.

This study reports the preparation, characterization, and electrocatalytic properties of palladium-based catalysts containing ceria (CeO 2 ) on carbon black (CB) and onion-like carbon (OLC) supports. The electrocatalysts (Pd− CeO 2 /CB and Pd−CeO 2 /OLC) exhibit a large specific surface area, pore volume, and small particle size, as well as enhanced interfacial interaction and synergy among Pd, CeO 2 , and OLC in Pd−CeO 2 /OLC that are valuable for improved electrocatalysis. The presence of CeO 2 in Pd−CeO 2 /OLC induces ca. 7% defects and modifies the electronic structure of the Pd/OLC interface, significantly improving the electrical conductivity due to enhanced charge redistribution, corroborated by density functional theory (DFT) calculations. Pd−CeO 2 /OLC displays the lowest adsorption energies (H*, OH*, and OOH*) among the series. For the hydrogen oxidation reaction (HOR), Pd−CeO 2 /OLC delivers significantly enhanced HOR (mass-specific) activities of 4.2 (8.1), 13.2 (29.6), and 15 (78.5) times more than Pd−CeO 2 /CB, Pd/OLC, and Pd/CB, respectively, with the best diffusion coefficient (D) and heterogeneous rate constant (k). Pd−CeO 2 /OLC also displays less degradation during accelerated durability testing. In an anion-exchange-membrane fuel cell (AEMFC) with H 2 fuel, Pd−CeO 2 /OLC achieved the highest peak power density of 1.0 W cm −2 at 3.0 A cm −2 as compared to Pd−CeO 2 /CB (0.9 W cm −2 at 2.2 A cm −2 ), Pd/OLC (0.6 W cm −2 at 1.7 A cm −2 ), and Pd/CB (0.05 W cm −2 at 0.1 A cm −2 ). These results indicate that Pd−CeO 2 /OLC promises to serve as a high-performing and durable anode material for AEMFCs.