Activity of platinum/carbon and palladium/carbon catalysts promoted by Ni2 P in direct ethanol fuel cells

Recent advances in zinc-air batteries: self-standing inorganic nanoporous metal films as air cathodes

Zinc-air batteries (ZABs) have promising prospects as next-generation electrochemical energy systems due to their high safety, high power density, environmental friendliness, and low cost. However, the air cathodes used in ZABs still face many challenges, such as the low catalytic activity and poor stability of carbon-based materials at high current density/voltage. To achieve high activity and stability of rechargeable ZABs, chemically and electrochemically stable air cathodes with bifunctional oxygen reduction reaction (ORR)/oxygen evolution reaction (OER) activity, fast reaction rate with low platinum group metal (PGM) loading or PGM-free materials are required, which are difficult to achieve with common electrocatalysts. Meanwhile, inorganic nanoporous metal films (INMFs) have many advantages as self-standing air cathodes, such as high activity and stability for both the ORR/OER under highly alkaline conditions. The high surface area, three-dimensional channels, and porous structure with controllable crystal growth facet/direction make INMFs an ideal candidate as air cathodes for ZABs. In this review, we first revisit some critical descriptors to assess the performance of ZABs, and recommend the standard test and reported manner. We then summarize the recent progress of low-Pt, low-Pd, and PGM-free-based materials as air cathodes with low/non-PGM loading for rechargeable ZABs. The structure-composition-performance relationship between INMFs and ZABs is discussed in-depth. Finally, we provide our perspectives on the further development of INMFs towards rechargeable ZABs, as well as current issues that need to be addressed. This work will not only attract researchers' attention and guide them to assess and report the performance of ZABs more accurately, but also stimulate more innovative strategies to drive the practical application of INMFS for ZABs and other energy-related technologies.

Electrospinning-Based Carbon Nanofibers for Energy and Sensor Applications

Carbon nanofibers (CNFs) are the most basic structure of one-dimensional nanometer-scale sp2 carbon. The CNF’s structure provides fast current transfer and a large surface area and it is widely used as an energy storage material and as a sensor electrode material. Electrospinning is a well-known technology that enables the production of a large number of uniform nanofibers and it is the easiest way to mass-produce CNFs of a specific diameter. In this review article, we introduce an electrospinning method capable of manufacturing CNFs using a polymer precursor, thereafter, we present the technologies for manufacturing CNFs that have a porous and hollow structure by modifying existing electrospinning technology. This paper also discusses research on the applications of CNFs with various structures that have recently been developed for sensor electrode materials and energy storage materials.

Efficient synergism of V2O5 and Pd for alkaline methanol electrooxidation

Efficient synergism of high valence state V and Pd nanoparticles imparted their high catalytic performance and anti-poisoning ability for alkaline methanol electrooxidation.

Core-shell structured PtRu nanoparticles@FeP promoter with an efficient nanointerface for alcohol fuel electrooxidation

In this study, a bottleneck was overcome for direct alcohol fuel cells using state-of-the-art PtRu catalysts for alcohol fuel oxidation. Herein, a core-shell structured PtRu catalyst system based on the emerging promoter FeP was developed that showed excellent catalytic performance for the oxidation of alcohol fuels. The surface spectrometric analysis and morphology observation confirmed the formation of a nanointerface of the PtRu shell and FeP core hybrid catalyst (PtRu@FeP), and efficient ligand effects and electronic effects were found to result from the noble metal active sites and adjacent promoter in the core-shell structure. The facile formation of oxygen-containing species and the strong electronic effects could activate the Pt active sites, leading to high catalytic performance. High anti-CO poisoning ability was found for this catalyst system when compared with the case of the benchmark commercial PtRu/C catalyst (110 mV less and 60 mV less as evaluated by the peak and onset potentials for CO oxidation, respectively). The PtRu@FeP catalysts also exhibited much higher catalytic activity and stability when compared with commercial and home-made PtRu/C catalysts; specifically, the peak current density of the PtRu@FeP 1 : 1 catalyst was about 2 and 3 times higher than those of the commercial PtRu/C catalyst and home-made PtRu/C for the oxidation of the alcohol fuels methanol and ethanol; moreover, high catalytic efficiency, improved by 2 times, was found, as expressed by the specific activity. Excellent catalytic stability as evaluated by 1000 cycles of cyclic voltammetry measurements was also demonstrated for the PtRu@FeP catalysts. The high catalytic performance could be attributed to the intimate nanointerface contact of the core-shell structured PtRu shell over the FeP core via a bi-functional catalytic mechanism and electronic effects based on the ligand effect in this catalyst system. The current study is a significant step to increase the PtRu catalytic performance via nanointerface construction by a core-shell structure on a novel promoter for direct alcohol fuel cells.

Nanocatalysts for Electrocatalytic Oxidation of Ethanol

The use of ethanol as a fuel in direct alcohol fuel cells depends not only on its ease of production from renewable sources, but also on overcoming the challenges of storage and transportation. In an ethanol-based fuel cell, highly active electrocatalysts are required to break the C-C bond in ethanol for its complete oxidation at lower overpotentials, with the aim of increasing the cell performance, ethanol conversion rates, and fuel efficiency. In recent decades, the development of wet-chemistry methods has stimulated research into catalyst design, reactivity tailoring, and mechanistic investigations, and thus, created great opportunities to achieve efficient oxidation of ethanol. In this Minireview, the nanomaterials tested as electrocatalysts for the ethanol oxidation reaction in acid or alkaline environments are summarized. The focus is mainly on nanomaterials synthesized by using wet-chemistry methods, with particular attention on the relationship between the chemical and physical characteristics of the catalysts, for example, catalyst composition, morphology, structure, degree of alloying, presence of oxides or supports, and their activity for ethanol electro-oxidation. As potential alternatives to noble metals, non-noble-metal catalysts for ethanol oxidation are also briefly reviewed. Insights into further enhancing the catalytic performance through the design of efficient electrocatalysts are also provided.

Carboxyethyltin and transition metal co-functionalized tungstoantimonates composited with polypyrrole for enhanced electrocatalytic methanol oxidation

Carboxyethyltin and first-row transition metals (TMs) were firstly introduced into trivacant Keggin-type tungstoantimonate in an aqueous solution, leading to the formation of four crystalline organic-inorganic hybrid sandwich-type polyoxometalates (POMs), formulated as Na10-x-yKyHx[((TM)(H2O)3)2(Sn(CH2)2COO)2(SbW9O33)2]·nH2O (SbW9-TM-SnR, TM = Mn, Co, Ni, Zn; x = 1, 1, 0, 0; y = 0, 5, 5, 2; n = 18, 24, 24, 22, respectively). SbW9-TM-SnR exhibit high catalytic ability for the oxidation of cyclohexanol. Meanwhile, SbW9-TM-SnR were composited with polypyrrole (PPy) through an electropolymerization process, forming PPy-SbW9-TM-SnR, on which platinum (Pt) was further electro-deposited to prepare PPy-SbW9-TM-SnR/Pt for electrocatalytic methanol (CH3OH) oxidation in acid solution. The composition and morphology of PPy-SbW9-TM-SnR/Pt were determined by IR, scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS). The electrochemical experimental results show that SbW9-TM-SnR and PPy obviously enhance the electrocatalytic and anti-intoxication abilities of Pt, and the highest peak current density of 0.87 mA cm-2, corresponding to 1.85 and 1.43 times higher than those of pure Pt and PPy/Pt electrodes respectively, is acquired for the PPy-SbW9-Ni-SnR/Pt composite electrode. These findings may enlarge the application of PPy and POMs in the electrocatalytic field.

Graphene-supported platinum/nickel phosphide electrocatalyst with improved activity and stability for methanol oxidation

In this paper, we report a novel catalyst using Ni₂P as a cocatalyst of Pt supported on graphene for methanol oxidation.

Facile synthesis of a molybdenum phosphide (MoP) nanocomposite Pt support for high performance methanol oxidation

Molybdenum phosphide nanocrystals anchored on graphitic carbon are facilely synthesized and MoP highly improves the catalytic activity and stability of Pt in methanol electro-oxidation.

Enhanced bioelectricity generation of double-chamber air-cathode catalyst free microbial fuel cells with the addition of non-consumptive vanadium(v)

Improvement of microbial fuel cells (MFCs) via bioelectricity recovery is urgently needed in micro-energy devices nowadays.

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.

Ethanol electro-oxidation on nanoworm-shaped Pd particles supported by nanographitic layers fabricated by electrophoretic deposition

Different morphologies of nanographitic flake coatings used as catalyst supports for nanoworm-shaped palladium (Pd) were fabricated via the electrophoretic deposition (EPD) of dispersed nanographitic flakes in isopropyl alcohol.