Reduced graphene oxide (RGO)-supported Pd–CeO2 nanocomposites as highly active electrocatalysts for facile formic acid oxidation

Reduced graphene oxide (RGO)-supported Pd–CeO2 nanoparticles prepared by a chemical reduction method were shown to exhibit superior electrocatalytic activity towards formic acid compared to the commercial Pd/C catalyst.

Electrochemically active site-rich nanocomposites of two-dimensional materials as anode catalysts for direct oxidation fuel cells: new age beyond graphene

Direct oxidation fuel cell (DOFC) has been opted as a green alternative to fossil fuels and intermittent energy resources as it is economically viable, possesses good conversion efficiency, as well as exhibits high power density and superfast charging. The anode catalyst is a vital component of DOFC, which improves the oxidation of fuels; however, the development of an efficient anode catalyst is still a challenge. In this regard, 2D materials have attracted attention as DOFC anode catalysts due to their fascinating electrochemical properties such as excellent mechanical properties, large surface area, superior electron transfer, presence of active sites, and tunable electronic states. This timely review encapsulates in detail different types of fuel cells, their mechanisms, and contemporary challenges; focuses on the anode catalyst/support based on new generation 2D materials, namely, 2D transition metal carbide/nitride or carbonitride (MXene), graphitic carbon nitride, transition metal dichalcogenides, and transition metal oxides; as well as their properties and role in DOFC along with the mechanisms involved.

Synthesis of PtCoNiRu/C nanoparticles by spray drying combined with reduction sintering for methanol electro-oxidation

The controllable synthesis of carbon-supported platinum-based multicomponent alloys is important for the development and application of direct methanol fuel cells (DMFCs). In this paper, controllable synthesis of carbon-supported PtCoNiRu quaternary alloy is realized by spray drying and reduction sintering. The effects of reduction temperature on the size, morphology and catalytic properties of the metal nanoparticles were investigated. The electrochemical performance of the as-synthesized PtCoNiRu/C catalysts towards methanol electro-oxidation was studied using cyclic voltammetry (CV) and chronoamperometry. The results show that metal nanoparticles with uniform size and dispersity on the carbon surface can be obtained at a suitable sintering temperature, while the catalyst has a higher electrochemical active surface area (ECSA) and shows better catalytic activity and stability for methanol electro-oxidation. The method described in this study provides a new route for the manufacture of Pt alloy nanoparticles with higher catalytic activity and stability.

A Pt-free graphenaceous composite as an electro-catalyst for efficient oxygen reduction reaction

Use of Pt-based electro-catalysts for the oxygen reduction reaction (ORR) is a major hindrance in large-scale application of proton exchange membrane fuel cells (PEMFCs). Hence, new, cost-effective and high performance electro-catalysts are required for the commercial success of PEMFCs. In this work, a Pt-free magnesium oxide (MgO) decorated multi-layered reduced graphene oxide (MLGO) composite is tested as an electro-catalyst for the ORR. The ORR activity of MgO/MLGO in terms of diffusion-controlled current density is found to be superior (6.63 mA per cm2-geo) than that of in-house prepared Pt/rGO (5.96 mA per cm2-geo) and commercial Pt/C (5.02 mA per cm2-geo). The applicability of less expensive MgO/MLGO not only provides a new electro-catalyst but also provides a new direction in exploring metal oxide-based electro-catalysts for the ORR.

Bimetallic Pt-Pd nanostructures supported on MoS2 as an ultra-high performance electrocatalyst for methanol oxidation and nonenzymatic determination of hydrogen peroxide

The authors report on a composite based electrocatalyst for methanol oxidation and H₂O₂ sensing. The composite consists of Pt nanoparticles (NPs), Pd nanoflakes, and MoS₂. It was synthesized by chemical reduction followed by template-free electro-deposition of Pt NPs. FESEM images of the Pd nanoflakes on the MoS₂ reveal nanorod-like morphology of the Pd NPs on the MoS₂ support, whilst FESEM images of the Pt-Pd/MoS₂ composite show Pt NPs in high density and with the average size of ~15 nm, all homogeneously electrodeposited on the Pd-MoS₂ composite. A glassy carbon electrode (GCE) was modified with the composite to obtain an electrode for methanol oxidation and H₂O₂ detection. The modified GCE exhibits excellent durability with good catalytic efficiency (the ratio of forward and backward peak current density, I_f/I_b, is 3.23) for methanol oxidation in acidic medium. It was also used to sense H₂O₂ at an applied potential of -0.35 V vs. Ag|AgCl which can be detected with a 3.4 μM lower limit of detection. The sensitivity is 7.64 μA μM^-1 cm^-2 and the dynamic range extends from 10 to 80 μM. This enhanced performance can be explained in terms of the presence of higher percentage of metallic 1T phase rather than a semiconducting 2H phase in MoS₂. In addition, this is a result of the high surface area of MoS₂ with interwoven nanosheets, the uniform distribution of the Pt NPs without any agglomeration on MoS₂ support, and the synergistic effect of Pt NPs, Pd nanoflakes and MoS₂ nanosheets. In our perception, this binder-free nano-composite has promising applications in next generation energy conversion and in chemical sensing. Graphical abstract A composite consisting of palladium nanoflakes and molybdenum disulfide was decorated with platinum nanoparticles and then placed on a glassy carbon electrode which is shown to be a viable electrocatalyst for both methanol oxidation and detection of hydrogen peroxide.

Magnetically recyclable reduced graphene oxide nanosheets/magnetite-palladium aerogel with superior catalytic activity and reusability

A two-step method was employed to synthesize reduced graphene oxide nanosheets/magnetite-palladium (rGSs/Fe₃O₄-Pd) aerogel, with excellent catalytic activity and recyclability. Firstly, graphene oxide nanosheet (GS) hydrogels were formed by the self-assembly of GSs during the hydrothermal process. Meanwhile, hematite (α-Fe₂O₃) and Pd nanoparticles (NPs) were synthesized and anchored onto the surface of the hydrogel. During heat-treatment, GSs were reduced to rGSs, while nonmagnetic α-Fe₂O₃NPs were converted to magnetic Fe₃O₄ NPs. The as-obtained rGSs/Fe₃O₄-Pd aerogel displayed a three-dimensional interconnected hierarchical porous architecture, which was rich in mesopores and macropores. Such a structure was suitable for catalysis, since it not only improved the mass diffusion and transport, but also readily exposed the catalytic Pd NPs to the reactants. The typical reduction of 4-nitrophenol was chosen as a model reaction to evaluate the catalytic performance of the aerogel. As anticipated, both the reaction rate constant and turn over frequency of the aerogel were much higher than those of the commercial Pd/C catalyst. Moreover, due to incorporation of Fe₃O₄ NPs, the rGSs/Fe₃O₄-Pd aerogel could be magnetically separated from the reaction solution and reused, without obvious loss of catalytic activity.

Wormlike micelle templated synthesis of mono- and bi-metallic nanochain networks with adjustable structure and constituents

A wormlike micelle templated attachment growth approach for the preparation of mono- and bi-metallic nanochain networks with adjustable structures and constituents is reported.