Using PdO and PbO as the starting materials to prepare a multi-walled carbon nanotubes supported composite catalyst (PdxPby/MWCNTs) for ethanol oxidation reaction (EOR)

For the first time, a novel composite catalyst, namely, a multi-walled carbon nanotubes (MWCNTs) supported palladium and lead catalyst (denoted as Pd_xPb_y/MWCNTs), was prepared through a hydrothermal method using PdO, PbO and MWCNTs as the starting materials. The electrocatalytic activities of the resultant catalysts towards EOR in 1M KOH were examined mainly by using CV, CA and EIS. The electrochemical measurement results indicated that the peak current of EOR in the forward potential scan on the catalyst of Pd₁Pb₁/MWCNTs was almost 9 times larger, plus about 100 mV decrease in the onset potential value of EOR, than that on the Pb-free catalyst. A very simple, cost-effective and scalable way to synthesize Pd and Pb composite electrocatalyst for EOR was presented in this work, which was very meaningful to the further commercialization of EOR.     

A dotted nanowire arrayed by 5 nm sized palladium and nickel composite nanopaticles showing significant electrocatalytic activity towards ethanol oxidation reaction (EOR)

To the best of our knowledge, this is the first time to report the preparation of a dotted nanowire arrayed by 5 nm sized palladium and nickel composite nanoparticles (denoted as Pd_xNi_y NPs) via a hydrothermal method using NU and PdO·H₂O as the starting materials. The samples prepared at the mass ratio of NU to PdO·H₂O 1:1, 1:2 and 2:1 were, respectively, nominated as catalyst c₁, c₂ and c₃. The chemical compositions of all synthesized catalysts were mainly studied by using X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS), revealing that metallic Ni was one main component of all prepared catalysts. Surprisingly, the main diffraction peaks appearing in the XRD patterns of all prepared catalysts were assigned to the metallic Ni rather than the metallic Pd. Very interestingly, as indicated by the TEM images, a large number of dotted nanowires arrayed by numerous equidistant 5 nm sized nanoparticles were distinctly exhibited in catalyst c₁. More importantly, when being used as electrocatalysts for EOR, all prepared catalysts exhibited an evident electrocatalytic activity towards EOR. In the cyclic voltammetry (CV) test, the peak current density of the forward peak of EOR on catalyst c₁ measured at 50 mV s^?1 was as high as 56.1 mA cm^?2, being almost 9 times higher than that of EOR on catalyst c₃ (6.3 mA cm^?2). Particularly, the polarized current density of EOR on catalyst c₁ at 3600 s, as indicated by the chronoamperometry (CA) experiment, was still maintained to be around 1.47 mA cm^?2, a value higher than the latest reported data of 1.3 mA cm^?2 (measured on the pure Pd/C electrode). Presenting a novel method to prepare dotted nanowires arranged by 5 nm sized nanoparticles and showing the significant eletrocatalytic activities of the newly prepared dotted nanowires towards EOR were the major contributions of this preliminary work.     

Synthesis of ultrafine low loading Pd–Cu alloy catalysts supported on graphene with excellent electrocatalytic performance for formic acid oxidation

Here, surfactant free composite catalysts (Pd–Cu/rGO) with Pd–Cu alloy nanoparticles uniformly distributed on graphene sheets are successfully prepared via a facile hydrothermal approach. Compared with pure Pd/rGO catalyst, the introduction of copper could dramatically enhance the performance of the catalyst in the electrocatalytic formic acid oxidation (FAO) due to the strain effect and the ligand effect. With the optimized atomic ratio of 3:1 between palladium and copper, the alloy nanoparticle shows the smallest size of 2.12 nm, thus endowing the composite catalyst with highest catalytic efficiency. With Pd load as low as 14.5%, a maximum mass current density of 1580 mA mg_Pd⁻¹, and residual current of 69.93 mA mg_Pd⁻¹ at 3000 s was achieved with our Pd₃Cu₁/rGO catalyst in the electrocatalytic FAO process.     

Promotion of palladium catalysis by silver for ethanol electro-oxidation in alkaline electrolyte

Bimetallic Pd_mAg alloy nanostructures (m being the atomic Pd/Ag ratio, m = 0.1–1.5), prepared through a simple co-reduction process, are employed as the catalysts toward ethanol electro-oxidation reaction (EOR). XPS results show that the electronic structure of Pd can be modified due to the presence of Ag, which is crucial for the enhancement of the catalytic performance of the Pd_mAg/C catalysts. It is found that the catalytic activity of Pd was strongly dependent on the composition of the Pd_mAg/C catalysts, with the best performance found with the Pd_0.5Ag/C. The mass-specific activity (MSA) and intrinsic activity (IA) data of Pd_0.5Ag/C is 3.6 and 2.4 times higher than that of the monometallic Pd/C catalyst, respectively, which might be ascribed to the electronic and synergistic effect. These findings would be promising in understanding the mechanism of EOR on Pd-based catalysts and designing the bimetallic catalysts for direct ethanol fuel cells and other applications.     

Unexpected facilitation of the pyrolysis products of potassium ferrocyanide to the electrocatalytic activity of a PdO based palladium iron composite catalyst towards ethanol oxidation reaction (EOR)

It was found, for the first time, that the pyrolysis products of potassium ferrocyanide (K₄[Fe(CN)₆]) could significantly promote the electrocatalytic activity of the PdO based palladium iron composite catalyst towards ethanol oxidation reaction (EOR). In this work, huge carbon spheres (abbreviated as HCSs) were prepared firstly via a pyrolysis method using glucose and 1-butyl-3-methylimidazolium tetrafluoroborate as the starting materials. Secondly, PdO based palladium iron composites supported on HCSs (noted as PdO–Pd–Fe/HCSs) were successfully fabricated through a pyrolysis procedure employing PdO·H₂O, HCSs and K₄[Fe(CN)₆] as the initial materials. When preparing PdO–Pd–Fe/HCSs, four different amounts of K₄[Fe(CN)₆] were respectively added in the preparation system producing four kinds of samples. The sample prepared in the absence of K₄[Fe(CN)₆] was nominated as sample b-0. And the samples prepared in the presence of 5, 10 and 20 mg K₄[Fe(CN)₆] were, respectively, labeled as sample b-5, b-10 and b-20. It was indicated by the XRD and XPS patterns that the metallic Pd particles were the main crystalline materials of above four samples. SEM images of all synthesized samples substantially demonstrated that the added amount of K₄[Fe(CN)₆] was a pivotal factor which could significantly affect the morphologies of the prepared samples. For sample b-0, besides some nanoparticles with a size close to 30 nm, a larger number of pores were created on the surface of the HCSs producing a honeycomb-shaped surface. Interestingly, aniseed shaped particles, cauliflower-like particles and irregular particles with a diameter more than 150 nm were, respectively, anchored on the HCSs surface of sample b-5, b-10 and b-20. Most of all, as indicated by CV and CA measurements, all the samples prepared in the presence of K₄[Fe(CN)₆] delivered much better electrocatalytic activities towards EOR when compared to the sample prepared with no addition of K₄[Fe(CN)₆]. For example, in the CV curves, the peak current density of the peak appearing in the positive potential scanning (peak f) for EOR on sample b-10 was nearly 6.4 times greater than that on sample b-0 (16.6 mA cm^?2 vs. 2.6 mA cm^?2). The significantly decreased charge transfer resistance and the remarkably enlarged electrochemical surface area were analyzed to be the main reasons for sample b-10 to exhibit the best electrocatalytic performance among all prepared samples. In general, a novel electrocatalyst consisting of PdO, Pd and the pyrolysis products of K₄[Fe(CN)₆] for EOR was developed in this work, which, due to its very lower preparation cost and its satisfied electrocatalytic activity towards EOR, was very helpful to the development of Pd-based EOR electrocatalyst.     

Enhanced electrocatalytic activity and stability of Pd nanoparticles supported on TiO2-modified nitrogen-doped carbon for ethanol oxidation in alkaline media

TiO₂-modified nitrogen-doped carbon (TiO₂-NC), prepared by a polymerization-pyrolysis process, is used to support the Pd catalyst for ethanol oxidation reaction (EOR) in alkaline media. X-ray photoelectron spectroscopy characterization indicates that the incorporation of TiO₂ and nitrogen into the carbon matrix could improve the percentage of Pd⁰ in Pd/TiO₂-NC catalyst. Electrochemical characterization shows that the Pd/TiO₂-NC catalyst presents higher electrocatalytic activity and stability for EOR than the nitrogen-doped carbon-supported Pd (Pd/NC) catalyst and the carbon black-supported Pd (Pd/CB) catalyst, which can be mainly attributed to the high percentage of Pd⁰ in Pd/TiO₂-NC catalyst (65%) than those in Pd/NC (48%) and Pd/CB (31%) catalysts. The results indicate that the Pd/TiO₂-NC catalyst holds great potential as high-performance anode catalyst for direct ethanol fuel cells.     

Carbon nanotube-copper oxide-supported palladium anode catalysts for electrocatalytic enhancement in formic acid oxidation

Pd/xCuO–10CNT (x = 1, 2, 3, 4) catalysts were synthesized using an improved polyol method. Uniformly prepared catalyst structures and chemical compositions of the catalysts delivered a high oxidation performance. The prepared catalysts were characterized via transmission electron microscopy (TEM), X-ray powder diffraction (XRD), Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS). The formation of homogenous active Pd metal and CuO nanoparticle-modified CNT surfaces was found. Meanwhile, the electrocatalytic activity and the long-term stability performance of the prepared catalysts toward formic acid oxidation reaction (FAOR) were also employed via cyclic voltammogram (CV) and chronoamperometry (CA), respectively. Prominently, the prepared Pd/xCuO–CNT nanocomposite catalyst presented an outstanding electrocatalytic performance with a higher maximum forward peak current density (26.9 mA cm^?2) than those of catalysts Pd/CNT (3.4 mA cm^?2) and Pd/C (2.3 mA cm^?2) toward FAOR in the H₂SO₄ electrolyte, representing high conductivity CNT, and dispersed Pd nanoparticles with a large active surface area, on the CuO-CNT support. Additionally, the prepared catalysts also had outstanding stability and an excellent CO poisoning tolerance through the modified Pd structures on CuO-supported CNT. The insertion of CuO onto the CNT surface before Pd loading provided additional electrochemical active sites due to the enhanced geometric and bifunctional system. CuO supports the adsorption of oxygen-containing species (OH_ads) on the catalyst surface, and the electron effect among Pd and Cu metals is beneficial for charge transfer.     

Self-standing foam-like Pd-based alloys nanostructures for efficient electrocatalytic ethanol oxidation

In this work, self-standing binary porous PdM (M = Ni, Fe and Co) foam-like nanostructures are rationally designed by a rapid and one-step aqueous-solution method, including ice co-reduction of metal precursors using sodium borohydride. Amongst the tested PdM nanostructures, the PdNi nanostructures delivered a superior alkaline ethanol oxidation reaction (EOR) activity and stability than those of PdFe, PdCo, and commercial Pd/C catalysts. The EOR mass activity of PdNi (4.81 A/mg_Pd) was 1.32, 1.51, and 24.05-folds of PdFe (3.62 A/mg_Pd), PdCo (3.19 A/mg_Pd) and Pd/C (0.2 A/mg_Pd), respectively based on equal Pd mass loading. This was attributed to the lower synergetic effect of PdNi, which enhanced activation/dissociation of H₂O to afford OH- species required for fast EOR kinetics; meanwhile, porous foam-like nanostructure improved electron mobility and increased accessible active sites. This study reveals that low synergism in porous PdM nanocrystals is beneficial for augmenting the EOR activity, which may allow the design of other binary Pd-based alloys for various electrocatalytic reactions.     

One‐pot synthesis of Pd‐MoO2/C by microwave sintering as an efficient electrocatalyst for ethanol oxidation reaction

The composite catalysts of Pd‐MoO₂/C for ethanol oxidation reaction (EOR) were prepared by microwave sintering. MoO₃ was thermally reduced to MoO₂ by carbon black in the preparing process of the Pd‐MoO₂/C material. The TEM analysis showed that Pd‐MoO₂ was well polymerized. Chronoamperometric, cyclic voltammetry, and electrochemical impedance spectra methods were applied to reveal the performance for EOR at room temperature. The Pd‐MoO₂/C electrode exhibited considerable high activity and stability. MoO₂ as a co‐catalyst significantly improved the catalytic activity of Pd‐MoO₂/C for EOR.     

Carbon nanodots prepared from NaOH-boiled graphene and its usage as a support of PdO for ethanol oxidation reaction

For the first time, carbon nanodots were prepared from NaOH-boiled graphene. And, a novel catalyst that contained PdO and carbon nanodots (denoted as PdO/CND) was fabricated in this work. In this work, 0.5 M and 1.5 M NaOH solutions were respectively employed with an intention to study the influence of NaOH concentration on the electrocatalytic activity of the obtained catalysts for ethanol oxidation reaction (EOR). The obtained samples were thoroughly characterized using X-ray diffraction (XRD), transmission electron microscopy (TEM) and fourier transform infrared spectrometry (FTIR). The results indicated that the intensities of the diffraction peaks for graphene were significantly promoted with increasing the NaOH concentration and carbon nanodots with an average particle size less than 4 nm were fabricated by this developed boiling–grinding–ultrasonication (BGU) method. The electrocatalytic performances of the obtained PdO/CND catalysts for EOR were investigated using cyclic voltammetry (CV) and chronoamperometry (CA). And the consequences strongly demonstrated that PdO/CND prepared from 0.5 M NaOH-boiled graphene showed the best electrocatalytic activity towards EOR among all the prepared catalysts. Developing a very facile method for producing carbon nanodots as well as a novel composite catalyst that contained PdO and carbon nanodots for EOR was the main contribution of this work.     

Comparison of Pt and Pd anode catalysts supported on nanocrystalline Ru–SnO2 for ethanol oxidation in fuel cell applications

The article presents promising catalysts, applicable for direct alcohol fuel cells (DAFC) for portable and mobile applications. The goal of this work is development of Pt and Pd catalysts deposited on interactive nanocrystalline Ru doped SnO₂ support with improved performance. The structure and the morphology of the prepared metal-oxide catalyst support and Pt and Pd based catalysts were examined using XRPD, SEM/EDX and TEM techniques. Electrocatalytic activities of the prepared Pt or Pd based catalysts were evaluated in both alkaline and acidic conditions. The ethanol oxidation reaction (EOR) was studied using conventional electrochemical techniques. The interactive nature of the novel Ru doped SnO₂ catalyst support was confirmed, resulting in the enhancement of the EOR kinetics, in comparison to commercially available catalysts. New and simplified synthetic route applied for preparation of interactive catalyst support was presented with the aim to enable easy scale-up of the catalyst production process. Obtained results on the novel catalysts promise great potential in improving the performance and durability of the DAFC.     

Scalable preparation of Pd/bacteria-rGO(CNT,Ketjen) composites for efficient oxygen reduction catalyst

In this paper, Pd catalysts supported on novel composite carbon supports were synthesized by the carbonization and hydrogen reduction of Pd²⁺-doped bacteria containing Ketjen EC600JD, CNT and rGO, respectively. The analysis results show that the prepared catalysts exhibit excellent ORR electrocatalytic performance in acid medium. The best ORR electrocatalytic performance was obtained for Pd/carbonized-bacteria-rGO, which exbibits a mass activity at 0.345 A mg^?1 that is 9.58 times higher than commercial Pd/C, and meanwhile displays a better stability than that of Pd/C. The enhanced performance can be attributed to nitrogen doping and flexible carbon-coating microstructure. Herein, we elaborate an efficient and ecofriendly method for the synthesis of electrocatalysts used for oxygen reduction reaction.     

Highly active Pt decorated Pd/C nanocatalysts for oxygen reduction reaction

This article describes findings of the correlation between the atomic scale surface structure and the electrocatalytic performance of nanoengineered Pt-Pd/C catalysts for oxygen reduction reaction (ORR), aiming at providing a new fundamental insight into the role of the detailed atomic decorated structure of the catalysts in fuel cell reactions. Carbon-supported Pt decorated Pd nanoparticles (donated as Pt-Pd/C), with Pt coverage close to a monolayer, were prepared from a simple galvanic replacement reaction between Pd/C particles and PtCl₄^2? at room temperature. The decorated architecture was confirmed by extensive microstructural characterization techniques, including TEM, XRD, XPS, HAADF-STEM, ICP and HS-LEIS. The catalysts were also examined for their intrinsic kinetic activities towards oxygen reduction reaction. The results have shown that the Pt-Pd/C catalysts are highly active towards molecular oxygen electrocatalytic reduction. These findings have profound implications to the design and nanoengineering of decorated surfaces of catalysts for oxygen reduction reaction.     

Pt modulates the electronic structure of Pd to improve the performance of Pd-based catalytic combustion catalyst

The electronic modulation between the catalytic active components can improve the catalytic activity and stability of the catalyst. The Pd-based catalysts can easily react with SO_X to form stable and inactive sulfates. In this paper, the Pd–Pt-based catalytic combustion catalyst was prepared by replacing part of Pd with a small amount of Pt. The storage tank VOCs catalytic combustion activity and the anti-SO₂ poisoning performance of the Pd–Pt-based catalyst and Pd-based catalyst were tested. The Pd 3d binding energy of each Pd-based catalyst was detected by XPS characterization, and the electronic structure changes of Pd active components was analyzed by the change of Pd 3d binding energy. The effect of electrons transfer between Pd and Pt on the improvement of catalytic combustion activity and SO₂ poisoning resistance of Pd-based catalysts was analyzed. The results show that the Pt addition can increase the electron cloud density of the Pd active components, and improve the performance of the Pd active components to adsorb and activate oxygen. The reaction of Pd and SO_X to form sulfate needs to gain electrons. The increase in the electron cloud density of the Pd active components in Pd–Pt-based catalyst makes it difficult for the Pd active components to adsorb SO_X and difficult to react with SO_X to form sulfate, thereby preventing the Pd active components from being poisoned and deactivated.     

A “special” anhydrous system for the preparation of alloyed Pd1Ce0.5 nanonetworks catalyst supported on carbon nanotubes with high electrochemical oxidation activity for formic acid

Herein, Pd₁Ce_0.5 alloy nanonetworks (ANNs) on multi-walled carbon nanotubes (MWCNTs) supported bimetallic catalyst (referred to Pd₁Ce_0.5/MWCNTs-D) was prepared in deep eutectic solvents (DESs). The Pd₁Ce_0.5/MWCNTs-D catalyst shows remarkable catalytic performance toward formic acid oxidation (FAO) (1968.5 mA mg_Pd^?1) and better CO anti-poisoning capability compare with Pd/MWCNTs-D, Pd/MWCNTs-W (prepared in water) and commercial Pd/C catalysts. The excellent network structure and synergistic effect are the main reasons for the improvement of electrochemical activity of Pd₁Ce_0.5/MWCNTs-D catalyst. This study provides a new method for preparation of high performance Pd-based electrocatalysts for direct formic acid fuel cell (DFAFC) applications.     

Enhancement of electrochemical properties of Pd/C catalysts toward ethanol oxidation reaction in alkaline solution through Ni and Au alloying

The effect of Au and/or Ni addition on the ethanol oxidation reaction (EOR) performance in alkaline media of Pd-based binary and ternary catalysts (Pd₃Au/C, Pd₃Ni/C, and Pd₃AuNi/C) is systematically elucidated. The EOR activities, structures, morphologies, surface compositions and surface species of the prepared catalysts are analyzed by cyclic voltammetry, X-ray diffraction and X-ray absorption spectroscopy, high resolution transmission electron microscopy, X-ray photoelectron spectroscopy, and temperature-programmed reduction, respectively. It is observed that the surface Ni with the chemical state of NiOOH can promote the EOR through bi-functional mechanism and spillover while surface Au can modify the Pd lattice and electron configuration which is helpful for the absorption of ethanol molecular. Chronoamperometric (CA) results obtained at room temperature demonstrate that the mass current density of ternary Pd₃AuNi/C catalysts after the long-term EOR test for 4 h is about 1.39 and 1.10 times higher than that of the monometallic Pd/C and binary Pd₃Au/C catalysts, respectively. It is proposed that the EOR stability enhancement of Pd₃AuNi can be attributed to the synergistic effect of Ni and Au alloying.     

Pd-Ni electrocatalysts for efficient ethanol oxidation reaction in alkaline electrolyte

Pd_xNi_y/C catalysts with high ethanol oxidation reaction (EOR) activity in alkaline solution have been prepared through a solution phase-based nanocapsule method. XRD and TEM show Pd_xNi_y nanoparticles with a small average diameter (2.4-3.2 nm) and narrow size distribution (1-6 nm) were homogeneously dispersed on carbon black XC-72 support. The EOR onset potential on Pd₄Ni₅/C (−801 mV vs. Hg/HgO) was observed shifted 180 mV more negative than that of Pd/C. Its exchange current density was 33 times higher than that of Pd/C (41.3 × 10⁻⁷ A/cm²vs. 1.24 × 10⁻⁷ A/cm²). After a 10,000-s chronoamperometry test at −0.5 V (vs Hg/HgO), the EOR mass activity of Pd₂Ni₃/C survived at 1.71 mA/mg, while that of Pd/C had dropped to 0, indicating Pd_xNi_y/C catalysts have a better ’detoxification’ ability for EOR than Pd/C. We propose that surface Ni could promote refreshing Pd active sites, thus enhancing the overall ethanol oxidation kinetics. The nanocapsule method is able to not only control over the diameter and size distribution of Pd-Ni particles, but also facilitate the formation of more efficient contacts between Pd and Ni on the catalyst surface, which is the key to improving the EOR activity.     

Remarkable activity of Pd catalyst supported on alumina synthesized via a hydrothermal route for hydrogen release of perhydro-N-propylcarbazole

The investigation of dehydrogenation catalysts to achieve rapidly hydrogen release of Liquid Organic Hydrogen Carriers (LOHCs) are of crucial importance for large-scale applications. The catalyst supports with bulk surface area and decent acid-base nature is a key parameter for catalyst to improve its catalytic performance as well as reduce precious metal dosage. Herein, alumina was chosen as a support for Pd loading and prepared through hydrothermal route at different temperatures. The morphology and surface acid property of the alumina supports were investigated in detail. The results revealed that the hydrothermal temperature had a closely effect on the morphology, surface acidity and specific surface area of alumina, resulting in a further impact on Pd dispersion and particle size associated tightly with catalytic activity of Pd/Al₂O₃. The catalyst with 1 wt% Pd loaded on alumina carrier prepared via hydrothermal treatment at 120 °C showed the best catalytic performance for dehydrogenation of perhydro-N-propylcarbazole (12H-NPCZ). Full dehydrogenation with 100% conversion to N-propylcarbazole (NPCZ) could be achieved after 360 min at 180 °C and 101 kPa, which is higher than that of commercial 5 wt% Pd/Al₂O₃ catalyst. The catalyst has potential commercial application value in large-scale application of LOHC technology.     

Pd nanoparticles supported on copper phthalocyanine functionalized carbon nanotubes for enhanced formic acid electrooxidation

The hydrothermal synthesis of a novel Pd electrocatalyst using copper phthalocyanine-3,4′,4″,4′″-tetrasulfonic acid tetrasodium salt (TSCuPc) functionalized multi-walled carbon nanotubes (MWCNTs) composite as catalyst support for Pd nanoparticles is reported. The prepared nanocomposites were characterized by UV–vis absorption spectroscopy, Fourier transform infrared (FTIR) spectroscopy, Raman spectroscopy, thermogravimetric analysis (TGA), X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and electrochemical tests. It is found that Pd nanoparticles are uniformly deposited on the surface of TSCuPc-MWCNTs, and their dispersion and electrochemical active surface area (ECSA) are significantly improved. Studies of cyclic voltammetry and chronoamperometry demonstrate that the Pd/TSCuPc-MWCNTs exhibits much higher electrocatalytic activity and stability than the Pd/AO-MWCNTs catalyst for formic acid oxidation. This study implies that the as-prepared Pd/TSCuPc-MWCNTs will be a promising candidate as an anode electrocatalyst in direct formic acid fuel cell (DFAFC).     

Use of graphene-supported manganite nano-composites for methanol electrooxidation

Binary nano-composites of palladium and a metal (Fe or Cu) manganite on graphene nanosheets (GNS) have been prepared by a microwave-assisted polyol reduction method and investigated as electrocatalysts for the methanol oxidation reaction (MOR) in 1 M KOH at 25 °C. Structural and electrocatalytic surface characterizations of composites are carried out by X-ray diffraction, transmission electron microscopy, X-ray photoelectron microscopy, cyclic voltammetry and chronoamperometry. Results show that new composite catalysts, particularly 40 wt%Pd–x wt%FeMn₂O₄/GNS (where x = 5, 8, 10 & 15) are MOR active and that the activity is the greatest with the catalyst containing 8 wt% of the oxide. The composite, Pd–8 wt%FeMn₂O₄/GNS, exhibits much superior catalytic activity as well as stability compared to the base (Pd/GNS) electrode. The enhanced catalytic activity and stability of the Pd/GNS catalyst in presence of the oxide can be ascribed to increased population of adsorbed OH⁻ ions/OH radicals at the electrode surface.