Synthesis of Pt-Ni (trace)/GNs composite and its bi-functional electrocatalytic properties for MOR and ORR

Chemical Surface Grafting of Pt Nanocatalysts for Reconciling Methanol Tolerance with Methanol Oxidation Activity

A conceptual challenge toward more versatile direct methanol fuel cells (DMFCs) is the design of a single material electrocatalyst with high activity and durability for both oxygen reduction reaction (ORR) and methanol oxidation reaction (MOR). This requires to conciliate methanol tolerance not to hinder ORR at the cathode with a good MOR activity at the anode. This is especially incompatible with Pt materials. We tackled this challenge by deriving a supramolecular concept where surface-grafted molecular ligands regulate the Pt-catalyst reactivity. ORR and MOR activities of newly reported Pt-calix[4]arenes nanocatalysts (Pt CF 3 ${{_{{\rm CF}{_{3}}}}}$ NPs/C) are compared to commercial benchmark PtNPs/C. Pt CF 3 ${{_{{\rm CF}{_{3}}}}}$ NPs/C exhibit a remarkable methanol tolerance without losing the MOR reactivity along with outstanding durability and chemical stability. Beyond designing single-catalyst material, operable in DMFC cathodic and anodic compartments, the results highlight a promising strategy for tuning interfacial properties.

Hierarchical Pt-In Nanowires for Efficient Methanol Oxidation Electrocatalysis

Direct methanol fuel cells (DMFC) have attracted increasing research interest recently; however, their output performance is severely hindered by the sluggish kinetics of the methanol oxidation reaction (MOR) at the anode. Herein, unique hierarchical Pt-In NWs with uneven surface and abundant high-index facets are developed as efficient MOR electrocatalysts in acidic electrolytes. The developed hierarchical Pt₈₉In₁₁ NWs exhibit high MOR mass activity and specific activity of 1.42 A mg_Pt^-1 and 6.2 mA cm^-2, which are 5.2 and 14.4 times those of Pt/C, respectively, outperforming most of the reported MORs. In chronoamperometry tests, the hierarchical Pt₈₉In₁₁ NWs demonstrate a longer half-life time than Pt/C, suggesting the better CO tolerance of Pt₈₉In₁₁ NWs. After stability, the MOR activity can be recovered by cycling. XPS, CV measurement and CO stripping voltammetry measurements demonstrate that the outstanding catalytic activity may be attributed to the facile removal of CO due to the presence of In site-adsorbing hydroxyl species.

Synthesis of Co/CeO2 hetero-particles with abundant oxygen-vacancies supported by carbon aerogels for ORR and OER

It is highly significant for the fabrication of rechargeable metal-air batteries to develop cost-efficient and high-performance electrocatalysts of bifunctionality for both oxygen evolution reaction (OER) and oxygen reduction reaction (ORR). Herein, we demonstrate a hybrid composed of CeO₂-decorated Co nanoparticles supported on three-dimensionally porous carbon aerogels (Co-CeO₂/C aerogels) as a superior bifunctional electrocatalyst. The preparation of Co-CeO₂/C aerogels depends on the formation of a novel CeCl₃/K₃Co(CN)₆-chitosan (CS) hydrogel, during which the cyanide groups of K₃Co(CN)₆ combines the hydroxyls in CS by hydrogen bridges, accompanying with the substitution of chloride groups in CeCl₃ by cyanide groups in K₃Co(CN)₆. The electron spin resonance offers a convincing proof that numerous oxygen vacancies were found in Co-CeO₂/C aerogels after the introduction of CeO₂. The developed Co-CeO₂/C aerogels showed an outstanding electrochemical performance for both OER and ORR in comparsion with RuO₂ and Pt/C catalysts in 0.1 M KOH solution. A small overpotential (380 mV) and a low Tafel slope (99 mV dec^-1) were observed for OER, while the half-wave potential (0.75 V) and the onset potential (0.92 V) were high for ORR. The superior performance could be put down to the multihole heterostructure, multiple components and abundant oxygen vacancies. It was very helpful for the adsorption and the catalyzation of the reactants and the efficient mass transport of reagent/product. This work paves a neoteric method to synthesize a bifunctional hybrid catalyst with a highly efficient performance of energy conversion and storage.

Core-shell Pd-P@Pt-Ni nanoparticles with enhanced activity and durability as anode electrocatalyst for methanol oxidation reaction

Pd–P@Pt–Ni core–shell nanoparticles, which consisted of a Pd–P alloy as a core and Pt–Ni thin layer as a shell, were explored as electrocatalysts for methanol oxidation reaction. The crystallographic information and the electronic properties were fully investigated by X-ray diffraction and X-ray photoelectron spectroscopy. In the methanol electrooxidation reaction, the particles showed high catalytic activity and strong resistance to the poisoning carbonaceous species in comparison with those of commercial Pt/C and the as-prepared Pt/C catalysts. The excellent durability was demonstrated by electrochemically active surface area loss and chronoamperometric measurements. These results would be due to the enhanced catalytic properties of Pt by the double synergistic effects from the core part and the nickel species in the shell part.

The Pd–P@Pt–Ni core–shell nanoparticles consist of an amorphous core and a low-crystalline shell. They exhibit the excellent catalytic properties in MOR owing to the double synergistic effects from the core and the nickel species in the shell.

Platinum nanoparticles-embedded raspberry-liked SiO2 for the simultaneous electrochemical determination of eugenol and methyleugenol

Based on platinum nanoparticle-embedded raspberry-liked SiO₂, a sensitive and selective electrochemical sensor was developed for simultaneous determination of eugenol (EU) and methyleugenol (MEU). Raspberry-liked SiO₂ (RL-SiO₂) was characterized with open pores on the surface, which can be used as a path for utilizing the inner space fully. So, platinum nanoparticles (Pt NPs) could be embedded in the inner and outer surface of RL-SiO₂. As a carrier, RL-SiO₂ not only avoided the agglomeration of the Pt NPs but also improved the catalytic performance. Therefore, the prepared Pt NPs@RL-SiO₂/GCE exhibited excellent electrocatalytic activity for simultaneous determination of EU and MEU; the linearity ranges were 0.50 ~ 60 μmol/L for EU at a working potential of 0.65 V (vs. saturated calomel electrode) and 0.50 ~ 50 μmol/L for MEU at a working potential of 1.10 V; the detection limits were 0.12 μmol/L and 0.16 μmol/L (S/N=3); and the relative standard deviations (RSDs) were 3.2% and 4.5%, respectively. In addition, Pt NPs@RL-SiO₂/GCE was successfully applied to the analysis of fish samples; the obtained recoveries were between 92.0 and 107%. Notably, the results conducted on samples were highly consistent with those obtained from high-performance liquid chromatography. It can be concluded that the study provided a simple method for simultaneous electrochemical determination of EU and MEU in fish samples. Schematic illustration of the preparation of RL-SiO2@Pt NPs/GCE for simultaneous determination of eugenol and methyleugenol in fish samples.

Pt-based (Zn, Cu) nanodendrites with enhanced catalytic efficiency and durability toward methanol electro-oxidation via trace Ir-doping engineering

Pt-based alloy nanomaterials with nanodendrites (NDs) structures are efficient electrocatalysts for methanol oxidation reaction (MOR), however their durability is greatly limited by the issue of transition metals dissolution. In this work, a facile trace Ir-doping strategy was proposed to fabricate Ir-PtZn and Ir-PtCu alloy NDs catalysts in aqueous medium, which significantly improved the electrocatalytic activity and durability for MOR. The as-prepared Ir-PtZn/Cu NDs catalysts showed distinct dendrites structures with the averaged diameter of 4.1 nm, and trace Ir doping subsequently improved the utilization of Pt atoms and promoted the oxidation efficiency of methanol. The electrochemical characterizations further demonstrated that the obtained Ir-PtZn/Cu NDs possessed enhanced mass activities of nearly 1.23 and 1.28-fold higher than those of undoped PtZn and PtCu, and approximately 2.35 and 2.67-fold higher than that of Pt/C in acid medium. More excitingly, after long-term durability test, the proposed Ir-PtZn and Ir-PtCu NDs still retained about 88.9% and 91.6% of its initial mass activities, which further highlights the key role of Ir-doping in determining catalyst performance. This work suggests that trace Ir-doping engineering could be a promising way to develop advanced electrocatalysts toward MOR for direct methanol fuel cell (DMFC) applications.

Highly selective and active Cu-In2O3/C nanocomposite for electrocatalytic reduction of CO2 to CO

The Cu-In₂O₃/C nanocomposite was prepared by a simple solid-phase reduction method. The introduction of In₂O₃ into Cu/C to form the Cu-In₂O₃/C nanocomposite evidently enhances the electrocatalytic activity for the selective reduction of CO₂ to CO. Specifically, the Cu-In₂O₃/C nanocomposite exhibits higher Faraday efficiency (FE = 86.7%) at -0.48 V vs. the reversible hydrogen electrode (RHE) in the electrocatalytic reduction of CO₂ to CO and larger current densities (55 mA cm^-2) under a low overpotential (-1.08 V vs. RHE). These indicate its superior performance over many of the reported Cu-based catalysts [1-4]. It was also found that by rationally adjusting the applied potential, tunable syngas can be formed, which can be used to synthesize formic acid, methyl ether, methanol, synthetic fuels, or other bulk chemicals through appropriate industrial processes. Furthermore, the Cu-In₂O₃/C nanocomposite maintains good stability in the electrocatalytic reduction of CO₂. This work demonstrates a novel strategy to convert CO₂ into desired products with high energy efficiency and large current density under low overpotential by the rational designing of non-precious metal catalysts.