Enhanced methanol oxidation and oxygen reduction reactions on palladium-decorated FeCo@Fe/C core–shell nanocatalysts in alkaline medium

Abstract

Palladium based nano-alloys are well known for their unique electrocatalytic properties. In this work, a palladium-decorated FeCo@Fe/C core-shell nanocatalyst has been prepared by a new method called microwave-induced top-down nanostructuring and decoration (MITNAD). This simple, yet efficient technique, resulted in the generation of sub-10 nm sized FeCo@Fe@Pd nanocatalysts (mainly 3-5 nm) from a micron-sized (0.21-1.5 mm) FeCo@Fe/C. The electrocatalytic activities of the core-shell nanocatalysts were explored for methanol oxidation reaction (MOR) and oxygen reduction reaction (ORR) in alkaline medium. A negative shift of 300 mV in the onset potential for MOR was observed, with a current thrice that of the Pd/C catalysts. A very low resistance to electron transfer (R ct ) was observed while the ratio of forward-to-backward oxidation current (I f /I b ) was doubled. The overpotential of ORR was significantly reduced with a positive shift of about 250 mV and twice the reduction current density was observed in comparison with Pd/C nanocatalysts with the same mass loading. The kinetic parameters (in terms of the Tafel slope (b) = À59.7 mV dec À1 (Temkin isotherm) and high exchange current density ( j o ) = 1.26 Â 10 À2 mA cm À2) provide insights into the favorable electrocatalytic performance of the catalysts in ORR in alkaline media. Importantly, the core-shell nanocatalyst exhibited excellent resistance to possible methanol cross-over during ORR, which shows excellent promise for application in direct alkaline alcohol fuel cells (DAAFCs).

Fe–Co hybrid oxides promoted Pd electrocatalysts with enhanced catalytic performance for ethylene glycol oxidation

“…Furthermore, it is confirmed to be a typical Pd (fcc) polycrystalline structure by selected area electron diffraction (SAED, Fig. 4a inserted) [24], which is consistent with the XRD observations. Based on 200 randomly selected nanoparticles, the size ranges from 1 to 10 nm.…”

“…For Pd/C, the anodic peak at À0.25 V is associated with the formation of Pd surface oxides, whereas the reduction of these oxides results in a well-defined cathodic peak at À0.18 V. The characteristic peaks in PdeFe 2-CoO x /C, PdeFeCoO x /C and PdeFeCo 2 O x /C catalysts show a little difference in locations and sizes compared to Pd/C, owing to the presence of metal oxides nanoparticles [23]. Electrochemical active surface area (EASA) is calculated by determining the coulombic charge for the reduction of Pd oxide as follows [24]:…”

Electro-oxidation of ethylene glycol and glycerol at palladium-decorated FeCo@Fe core–shell nanocatalysts for alkaline direct alcohol fuel cells: functionalized MWCNT supports and impact on product selectivity

“…[33][34][35] In the present study, MWCNT-COOH and MWCNT-SO 3 H are used as supports rather than the Vulcan XC-72. First, FeCo@Fe/MWCNT-COOH and FeCo@Fe/MWCNT-SO 3 H core-shell nanoalloys were obtained by a simple reduction method via hydrogenation.…”

“…Recently, we introduced Pd-based ternary core-shell with a bimetallic (FeCo) core supported on commercial Vulcan carbon XC-72 (i.e., FeCo@Fe@Pd/C) via "microwave-induced top-down nanostructuring and decoration" (MITNAD) strategy. [33][34][35] The MITNAD strategy is simply the adoption of fast microwave irradiation for a one-step top-down nanosizing of large-sized soft magnetic FeCo@Fe/C core-shell material (0.21-1.5 microns) to sub-10 nm sized Pd-coated structure, FeCo@Fe@Pd/C. In the present work, we have interrogated the use of two differently chemically-functionalized multi-walled carbon nanotubes (MWCNTs) bearing mainly the -COOH or -SO 3 H surface groups (abbreviated herein as MWCNT-COOH and MWCNT-SO 3 H, respectively), as supporting platforms for the FeCo@Fe@Pd catalyst.…”

Promotional Effects of Nanodiamond‐Derived Onion‐Like Carbons on the Electrocatalytic Properties of Pd‐MnO2 for the Oxidation of Glycerol in Alkaline Medium

“…The MnO 2 ‐Pd/OLC and Pd/OLC catalysts were prepared using a method that has recently been reported, with little modification. Briefly, catalysts were obtained from the mixture of OLC and PdCl 2 , as well as KMnO 4 , OLC and PdCl 2 in ethylene glycol solution and subjecting the mixture to rapid microwave irradiation at 500 W, 80 bars, and ∼198 °C for 15 minutes using the Anton Parr Synthos 3000 microwave reactor.…”