Nanocomposite with Promoted Electrocatalytic Behavior Based on Bimetallic Pd–Ni Nanoparticles, Manganese Dioxide, and Reduced Graphene Oxide for Efficient Electrooxidation of Ethanol

Abstract

In this work, a nanocomposite containing manganese dioxide (MnO2) modified reduced graphene oxide (rGO) supported bimetallic palladium–nickel (Pd–Ni) catalyst is prepared by electrodeposition method. The nanocomposite modifier film is prepared by forming a thin layer of graphene oxide (GO) via drop-casting of GO nanosheet dispersion on glassy carbon electrode (GCE), followed by electrochemical reduction of the film to provide rGO/GCE. Then, a two-step potential procedure is applied to deposit MnO2 nanoparticles on rGO/GCE. At the optimum deposition conditions, MnO2 nanoparticles with a thickness of 30–50 nm homogeneously covered the rGO surface (MnO2/rGO/GCE). Finally, the bimetallic Pd–Ni nanoparticles are electrodeposited on MnO2/rGO/GCE at a fixed potential to form a uniform dispersion with an average particle size of about 50 nm (Pd–Ni–MnO2/rGO/GCE). The morphology and crystalline structure of the prepared nanocomposites are characterized using XRD, SEM, EDX, FTIR, AFM, and Raman spectroscopy. The catalytic activities of different electrodes based on Pd/GCE, Pd/C/GCE, Pd/rGO/GCE, Pd–Ni/rGO/GCE, and Pd–Ni/MnO2/rGO/GCE for ethanol oxidation are compared using cyclic voltammetry, chronoamperometry, and electrochemical impedance spectroscopy (EIS). The results revealed significantly higher electroactive surface area (ECSA), higher catalytic activity, and better stability of Pd–Ni–MnO2/rGO/GCE toward the electrooxidation of ethanol compared to the other electrodes. The overall results corroborate the role of MnO2, Ni, and rGO as important constituents that significantly improve the electrocatalytic behavior, stability, and CO poisoning tolerance of Pd during the electrooxidation process. Thus, the prepared Pd–Ni–MnO2/rGO/GCE catalyst can be considered as a promising anode catalyst for alkaline direct ethanol fuel cells.

Palladium Nanoparticles with Surface Enrichment of Palladium Oxide Species Immobilized on the Aniline-Functionalized Graphene As an Advanced Electrocatalyst of Ethanol Oxidation

“…Two distinct peaks are visibly found in the presented CVs (Figure C). The anodic peak in the forward scan is derived from the electrooxidation of ethanol, and the other peak in the backward scan is ascribed to removal of the incompletely oxidized carbonaceous species . The anodic peak current densities ( j f ) including mass activity (normalized to the mass of Pd loading) and specific activity (normalized to the ECSA) in the forward scan are used to evaluate the EOR electrocatalytic activity (Figure D and Table ).…”

“…Figure E shows the plots of the j f as a function of the scan number in the accelerated degradation tests. Because of efficient elimination of the pollutants from the Pd active sites, the j f increases during the initial cycles . After the initial cycles, the j f decreases gradually with successive scans due to the surface poisoning and change of the catalyst structure .…”

Nanocatalysts for Electrocatalytic Oxidation of Ethanol

“…[213] They synthesized WCÀPd nanocomposites on graphene, in which small-sized Pd nanoparticles were decorated on the surfaceso fW C. Both DFT calculations and Xray photoelectrons pectroscopy( XPS) measurements confirm that there is as trong interaction betweenP da nd WC domains, which results in electron transfer from WC to Pd in the WCÀPd nanocomposites. [217][218][219][220][221][222][223][224][225][226][227][228][229][230][231][232] The enhanced EOR is derived first from surfaces rich in oxygen-containing species providedb yt he metal oxides, which are capable of removing adsorbed poisonous CO intermediates by facilitating oxidation to CO 2 .S econd, the "OH carpet" created by metal oxidesc ould precludeP t, Pd, or their alloys with other metals (e.g.,R h, Ru) from reacting with water to form compounds with ÀOH species, making them in lowcoordination states and available for ethanol oxidation. Electron transfer from WC to Pd in the nanocomposites not only modifies the electronic structure of the Pd domain,w hich is favorable for the scission of ethanol molecules on Pd sites, but also weakenst he adsorption of poisoning intermediates, such as CO, on the Pd surface by increasing the electron density around Pd atoms.…”

“…[215,216] Noble metals, such as Pt and Pd, werec onventionally integratedw ith transition-metal oxidest of orm nanocomposites to enhancet heir electrocatalytic performance in the EOR. [217][218][219][220][221][222][223][224][225][226][227][228][229][230][231][232] The enhanced EOR is derived first from surfaces rich in oxygen-containing species providedb yt he metal oxides, which are capable of removing adsorbed poisonous CO intermediates by facilitating oxidation to CO 2 .S econd, the "OH carpet" created by metal oxidesc ould precludeP t, Pd, or their alloys with other metals (e.g.,R h, Ru) from reacting with water to form compounds with ÀOH species, making them in lowcoordination states and available for ethanol oxidation. [200] The use of ac onducting polymer, [233,234] transition-metal phosphate, [235,236] and silicon, [237] to form nanocomposites with Pt or Pd for promoting their electrocatalytic activity for the EOR has also been reported.…”

One-Step Microwave-Assisted Synthesis of PtNiCo/rGO Electrocatalysts with High Electrochemical Performance for Direct Methanol Fuel Cells

“…Fuel cells have been considered green energy, renewable, and efficient energy devices in recent years due to environmental and energy challenges [ 1 ]. Direct methanol fuel cells (DMFCs) have attracted significant attention due to their high energy density and the abundance of liquid methanol [ 2 , 3 ]. The advantages of DMFCs are the simple structure of the system [ 4 ], low pollution [ 5 ], low operating temperature [ 6 ], and high energy conversion efficiency.…”