Particle size effects of PtRu nanoparticles embedded in TiO2 on methanol electrooxidation

Hydrogenated TiO2 Carbon Support for PtRu Anode Catalyst in High-Performance Anion-Exchange Membrane Fuel Cells

The availability of durable, high-performance electrocatalysts for the hydrogen oxidation reaction (HOR) is currently a constraint for anion-exchange membrane fuel cells (AEMFCs). Herein, a rapid microwave-assisted synthesis method is used to develop a core-shell catalyst support based on a hydrogenated TiO2/carbon for PtRu nanoparticles (NPs). The hydrogenated TiO2 provides a strong metal-support interaction with the PtRu NPs, which improves the catalyst's oxophilicity and HOR activity compared to commercial PtRu/C and enables greater size control of the catalyst NPs. The as-synthesized PtRu/TiO2/C-400 electrocatalyst exhibits respectable performance in an AEMFC operated at 80 °C, yielding the highest current density (up to 3× higher) within the catalytic region (compared at 0.80-0.90 V) and voltage efficiency (68%@ 0.5 A cm-2) values in the compared literature. In addition, the cell demonstrates promising short-term voltage stability with a minor voltage decay of 1.5 mV h-1. This "first-of-its-kind in alkaline" work may open further research avenues to develop rapid synthesis methods to prepare advanced core-shell metal-oxide/carbon supports for electrocatalysts for use in the next-generation of AEMFCs with potential applicability to the broader electrochemical systems research community.

Enhanced performance of glycerol electro-oxidation in alkaline media using bimetallic Au-Cu NPs supported by MWCNTs and reducible metal oxides

Electrochemical technologies for valorizing glycerol, a byproduct of biodiesel production, into electric energy and value-added chemical products continue to be technologically and economically challenging. In this field, an ongoing challenge is developing more active, stable, and low-cost heterogeneous catalysts for the glycerol electro-oxidation reaction (GlyEOR). This paper reports the influence of the preparation procedure, which involves intermatrix synthesis (Cu and Au NPs), followed by galvanic displacement (Cu-Au NPs) in previously functionalized multi-walled carbon nanotubes (MWCNTs). It also discusses the role of the supports, CeO₂ NPs, and TiO₂ NPs, obtained by a hydrothermal microwave-assisted procedure, on the electroactivity of a hybrid bimetallic Cu-Au/MWCNT/MO₂ catalyst in the GlyEOR in alkaline media. The electrocatalytic behavior was studied and discussed in terms of structure, composition, and electroactivity of the synthesized materials, which were determined by Fourier-transform infrared spectroscopy (FTIR), flame atomic absorption spectroscopy (FAAS), transmission electron microscopy (TEM), scanning transmission electron microscopy (STEM), X-ray photoelectronic spectroscopy (XPS), and cyclic voltammetry (CV). In addition, the role of the oxidation states of Cu and Au in the as-prepared catalysts (Cu/MWCNT, Au/MWCNT, Cu-Au/MWCNT, Cu-Au/MWCNT-CeO₂, and Cu-Au/MWCNT-TiO₂) was demonstrated. It was concluded that the preparation method of metal NPs for the controlled formation of the most catalytically active oxidation states of Cu and Au, together with the presence of a conductive and oxophilic microenvironment provided by carbon nanotubes and facile reducible oxides in optimized compositions, allows for an increase in the catalytic performance of synthesized catalysts in the GlyEOR.

Ni2P Makes Application of the PtRu Catalyst Much Stronger in Direct Methanol Fuel Cells

PtRu is regarded as the best catalyst for direct methanol fuel cells, but the performance decay resulting from the loss of Ru seriously hinders commercial applications. Herein, we demonstrated that the presence of Ni2 P largely reduces Ru loss, which thus makes the application of PtRu much stronger in direct methanol fuel cells. Outstanding catalytic activity and stability were observed by cyclic voltammetry. Upon integrating the catalyst material into a practical direct methanol fuel cell, the highest maximum power density was achieved on the PtRu-Ni2P/C catalyst among the reference catalysts at different temperatures. A maximum power density of 69.9 mW cm(-2) at 30 °C was obtained on PtRu-Ni2P/C, which is even higher than the power density of the state-of-the-art commercial PtRu catalyst at 70 °C (63.1 mW cm(-2)). Moreover, decay in the performance resulting from Ru loss was greatly reduced owing to the presence of Ni2 P, which is indicative of very promising applications.

Platinum particles supported on mesoporous carbons: fabrication and electrocatalytic performance in methanol-tolerant oxygen-reduction reactions

In this report, we describe the preparation and electrochemical characterization of a Pt electrocatalyst, which was synthesized from hexachloroplatinic acid, using the incipient wetness impregnation method. This carbon mesoporous materials (Pt-CMMs) electrocatalyst was used for catalyzing the oxidation of methanol and its oxygen-reduction reaction. The electrocatalytic oxidation of methanol was studied using linear-sweep voltammograms (LSV), polarization and chronoamperometric measurements. Phase characterizations and morphological analyses were performed using 3D excitation-emission fluorescent matrix (EEFM) spectroscopy, UV-Vis absorption measurements, and X-ray diffraction (XRD) and environmental scanning electron microscopy (ESEM) techniques; the ESEM system was equipped with an energy-dispersive spectrometer (EDS). The oxidation capacity measured using a LSV might explain the high activity exhibited by the Pt-CMM electrocatalysts in methanol-tolerant oxygen reduction, and the results demonstrated that the potential and current density of the main reaction peak of the Pt-CMMs electrocatalyst changed during the reaction. Moreover, EEFM spectroscopy and XRD were determined to be appropriate and effective methods for characterizing Pt clusters that enhance their intrinsic emission from Pt-CMMs electrocatalysts in electrocatalytic-treatment systems. Furthermore, the ESEM-EDS results showed that fresh Pt nanoparticles were highly dispersed on CMMs and featured a 20 nm diameter and a narrow particle-size distribution.

A simple template-free 'sputtering deposition and selective etching' process for nanoporous thin films and its application to dye-sensitized solar cells

A facile and straightforward method is suggested to synthesize nanoporous-TiO₂ thin films for dye-sensitized solar cells (DSSCs). Silver/TiO₂ co-sputtering led to the formation of nanocomposite films which consisted of silver nanoclusters with surrounding TiO₂ matrices, and metal particles were subsequently etched by just immersing in nitric acid. Nanoporous-TiO₂ DSSCs fabricated by this simple and effective process showed power-conversion efficiencies of up to 3.4% at a thickness of only 1.8 μm, which is much superior to that of conventional nanoparticulate-TiO₂ DSSCs with similar thickness.