Solvothermal synthesis of Pt -SiO2/graphene nanocomposites as efficient electrocatalyst for methanol oxidation

Advancements in Noble Metal-Decorated Porous Carbon Nanoarchitectures: Key Catalysts for Direct Liquid Fuel Cells

Noble-metal nanocrystals have emerged as essential electrode materials for catalytic oxidation of organic small molecule fuels in direct liquid fuel cells (DLFCs). However, for large-scale commercialization of DLFCs, adopting cost-effective techniques and optimizing their structures using advanced matrices are crucial. Notably, noble metal-decorated porous carbon nanoarchitectures exhibit exceptional electrocatalytic performances owing to their three-dimensional cross-linked porous networks, large accessible surface areas, homogeneous dispersion (of noble metals), reliable structural stability, and outstanding electrical conductivity. Consequently, they can be utilized to develop next-generation anode catalysts for DLFCs. Considering the recent expeditious advancements in this field, this comprehensive review provides an overview of the current progress in noble metal-decorated porous carbon nanoarchitectures. This paper meticulously outlines the associated synthetic strategies, precise microstructure regulation techniques, and their application in electrooxidation of small organic molecules. Furthermore, the review highlights the research challenges and future opportunities in this prospective research field, offering valuable insights for both researchers and industry experts.

Stimulation of ethylene glycol electrooxidation on electrodeposited Ni–PbO2–GN nanocomposite in alkaline medium

In this work, a novel system composed of non-precious nickel-based metal oxide/reduced graphene oxide nanocomposite (Ni–PbO2–GN) is used for electrooxidation of ethylene glycol (EG) in 1.0 M NaOH solution and compares its activity with that of Ni, Ni–GN, and Ni–PbO2. The facile electrodeposition technique is used to prepare the catalysts on glassy carbon (GC) substrates. The outcomes of electrochemical measurements show a high performance towards EG oxidation is obtained for Ni-nanocomposite electrodes compared to that of Ni mainly due to their higher surface areas. The excellent electrocatalytic properties of the Ni-nanocomposite could be ascribed to the synergistic contributions of PbO2 and graphene (GN) nano-sheets that help the reduction of Ni grains. A smaller charge transfer resistance value of 34.5 Ω cm2 for EG oxidation reaction at + 360 mV is recorded for GC/Ni–PbO2–GN compared to the other prepared electrodes. Moreover, it exhibits higher kinetic parameters of EG such as diffusion coefficient (D = 3.9 × 10–10 cm2 s−1) and charge transfer rate constant (ks = 32.5 mol−1 cm3 s−1). The overall performance and stability of the prepared catalysts towards EG electrooxidation have been estimated to be in the order of GC/Ni–PbO2–GN > GC/Ni–GN > GC/Ni–PbO2 > GC/Ni.

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Catalyst Composites of Palladium and N-Doped Carbon Quantum Dots-Decorated Silica and Reduced Graphene Oxide for Enhancement of Direct Formic Acid Fuel Cells

Pd-based catalysts consisting of Pd nanoparticles on nitrogen-doped carbon quantum dots (N-CQDs) modified silica (SiO₂) and reduced graphene oxide have been synthesized through reduction for use as catalysts for improved formic acid oxidation. The structure, morphology, chemical composition, functional groups, and porosity of the synthesized catalysts were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared (FT-IR) spectroscopy, Raman spectroscopy, and Brunauer-Emmett-Teller (BET) spectroscopy, respectively. Their electrocatalytic activities were also evaluated by electrochemical measurements. The differences in the average particle sizes found for Pd/N-CQDs-SiO₂-rGO, Pd/N-CQDs-rGO, and Pd/rGO were 4.81, 5.56, and 6.31 nm, respectively. It was also found that the Pd/xN-CQDs-SiO₂-yrGO composite catalysts (where x and y is 1 to 4) can significantly improve the activity and stability toward formic acid electrooxidation compared with Pd/rGO and commercial Pt/C. The mass activities of Pd/N-CQDs-SiO₂-rGO, Pd/N-CQDs-rGO, and Pd/rGO were 951.4, 607.8, and 157.6 mA g^-1, respectively, which was ca. 6-7 times compared with Pd/rGO and approximately 3-4 times compared with commercial Pt/C. With low potential for CO oxidation and high current intensity, the composites of rGO, SiO₂, and N-CQDs into Pd-based catalysts improved the catalytic activity of the prepared catalyst for the oxidation of formic acid in acidic media. The value of the Tafel slope designated that the chief path of the prepared catalysts is the dehydrogenation process. These prepared catalysts exhibit promise toward the development of high-performance Pd-based electrocatalysts for formic acid oxidation.

Influence of Solvents on the Electroactivity of PtAl/rGO Catalyst Inks and Anode in Direct Ethanol Fuel Cell

This paper presents research on the effects of common solvents such as n-butyl acetate, isopropanol, and ethanol on the properties and electroactivity of catalyst ink based on PtAl/rGO. The inks prepared by mixing PtAl/rGO catalyst, Nafion solution (5 wt%), and solvent were coated on carbon cloth by the spin coating method. The results obtained showed that ethanol was the most suitable solvent for the preparation of catalyst ink with a volume ratio between catalyst slurry and solvent of 1 : 1 (CI-EtOH (1/1) ink). The surface of the CI-EtOH (1/1) coated electrode was smooth, flat, and even and had no cracks due to the increase of Nafion mobility, resulting in significant improvement in the interaction between Pt particles and ionomer. Moreover, the electrochemical activity of the CI-EtOH (1/1) ink in ethanol electrooxidation reaction, in both acidic and alkaline media, has the highest value, with the forward current density, IF, reaching 1793 mA mgPt−1 and 4751 mA mgPt−1, respectively. In the application in direct ethanol fuel cell (DEFC), the CI-EtOH ink-coated anode also exhibited the highest power density in both PEM-DEFC (with a proton exchange membrane) and AEM-DEFC (with an anion exchange membrane) at 19.10 mW cm−2 and 27.07 mW cm−2, respectively.

Synthesis and applications of CaCO3/HPC core-shell composite subject to heavy metals adsorption processes

Core-shell particles are a class of materials from nanostructures that have received increased attention recently due to their interesting properties and wide range of applications in catalysis, biology, chemistry of materials and sensors. Simple and cost-effective one-pot synthesis route to directly prepare CaCO₃@highly porous carbon microsphere in a core–shell structure (denoted as CaCO₃/HPC) had been developed as a high-performance heavy metals sorbent. XRD (X-Ray Diffraction), SEM (scanning electron microscopy), Raman, FTIR (Fourier Transform Infrared Spectroscopy) and BET tools were used in structure characterization of the products. The adsorption properties of the products obtained were studied. From this study the adsorption performances of CaCO₃/HPCwere found to be optimal by comparing the maximum adsorption capacity of heavy metal ions (Pb (II) and Co(III)) with CaCO₃/HPC.The adsorption of CaCO₃/HPCtest to Pb(II) and Co(III), in particular Pb(II) had a good effect over a wide pH range (pH 2–7). The maximum adsorption capacitiesof CaCO₃/HPC for Pb (II) and Co(III) were 677.6 mg/g, and 308.5 mg/g, respectively, at pH = 6 (lead ion was 5.5) and 25 °C, and the adsorption rate was fast. The lead ions can be adsorbed almost entirely in 5 minutes and only 0.2 g/L was the best effective doseof adsorbent. The prepared and carefully testednanocomposites had been found to be of excellent performances in adsorption and in analytical regeneration. The adsorption processof Pb(II) and Co(III) through core shell of the preparednanocomposite adsorbent was found to be a second-order chemical adsorption and fit for Langmuir and Freundlich isotherms, in the form of amonomolecular and multi-layer heavy metal adsorptionprocesses. The (CaCO₃/HPC)-based sorbents (with and without) pelletization shows superior heavy metals adsorption performances compared to a CaCO₃-based sorbent.

High performance Pt/Ti3O5Mo0.2Si0.4 electrocatalyst with outstanding methanol oxidation activity

The strong metal–support interaction in Pt/Ti₃O₅Mo_0.2Si_0.4 enhances the methanol oxidation activity by decreasing the charge transfer resistance and activation energy.

Localization of platinum nanoparticles on inner walls of mesoporous hollow carbon spheres for improvement of electrochemical stability

Mesoporous hollow carbon spheres with Pt nanoparticles (NPs) loaded on their inner walls (Pt@HC-meso) have been designed and prepared through a dual-templating method. The core-shell structured Pt/SiO₂@micelle-polydopamine (PDA) precursor is obtained by first depositing Pt NPs on silica spheres and then coating them with the carbon precursor of PDA and diblock copolymer micelles as soft templates. The subsequent carbonization and KOH etching convert the micelle-PDA shells into mesoporous carbon and remove the silica cores, respectively. Thus, the Pt NPs are subjected to calcination and left on the inner walls. The fabricated Pt@HC-meso achieved high electrocatalytic performance and outstanding stability in catalyzing methanol oxidation. We infer that the mesoporous carbon shells not only provide accessible diffusion pathways for the reactants, but also protect the inner Pt NPs from collision with Pt NPs in other hollow carbon spheres. Each hollow carbon sphere with Pt NPs inside can be regarded as an independent nanoreactor. Moreover, observations of the morphology have proved that the calcined Pt NPs avoid a second aggregation during the electrocatalytic process and maintain long-term stability.