Fuel cells powered by hydrogen from secure and renewable sources are the ideal solution for non-polluting vehicles, and extensive research and development on all aspects of this technology over the past fifteen years has delivered prototype cars with impressive performances. But taking the step towards successful commercialization requires oxygen reduction electrocatalysts--crucial components at the heart of fuel cells--that meet exacting performance targets. In addition, these catalyst systems will need to be highly durable, fault-tolerant and amenable to high-volume production with high yields and exceptional quality. Not all the catalyst approaches currently being pursued will meet those demands.

Electrocatalyst approaches and challenges for automotive fuel cells

There is still an ongoing effort to search for sustainable, clean and highly efficient energy generation to satisfy the energy needs of modern society. Among various advanced technologies, electrocatalysis for the oxygen evolution reaction (OER) plays a key role and numerous new electrocatalysts have been developed to improve the efficiency of gas evolution. Along the way, enormous effort has been devoted to finding high-performance electrocatalysts, which has also stimulated the invention of new techniques to investigate the properties of materials or the fundamental mechanism of the OER. This accumulated knowledge not only establishes the foundation of the mechanism of the OER, but also points out the important criteria for a good electrocatalyst based on a variety of studies. Even though it may be difficult to include all cases, the aim of this review is to inspect the current progress and offer a comprehensive insight toward the OER. This review begins with examining the theoretical principles of electrode kinetics and some measurement criteria for achieving a fair evaluation among the catalysts. The second part of this review acquaints some materials for performing OER activity, in which the metal oxide materials build the basis of OER mechanism while non-oxide materials exhibit greatly promising performance toward overall water-splitting. Attention of this review is also paid to in situ approaches to electrocatalytic behavior during OER, and this information is crucial and can provide efficient strategies to design perfect electrocatalysts for OER. Finally, the OER mechanism from the perspective of both recent experimental and theoretical investigations is discussed, as well as probable strategies for improving OER performance with regards to future developments.

Electrocatalysis for the oxygen evolution reaction: recent development and future perspectives

The lithium metal battery is strongly considered to be one of the most promising candidates for high-energy-density energy storage devices in our modern and technology-based society. However, uncontrollable lithium dendrite growth induces poor cycling efficiency and severe safety concerns, dragging lithium metal batteries out of practical applications. This review presents a comprehensive overview of the lithium metal anode and its dendritic lithium growth. First, the working principles and technical challenges of a lithium metal anode are underscored. Specific attention is paid to the mechanistic understandings and quantitative models for solid electrolyte interphase (SEI) formation, lithium dendrite nucleation, and growth. On the basis of previous theoretical understanding and analysis, recently proposed strategies to suppress dendrite growth of lithium metal anode and some other metal anodes are reviewed. A section dedicated to the potential of full-cell lithium metal batteries for practical applicatio...

Toward Safe Lithium Metal Anode in Rechargeable Batteries: A Review.

5.1. Nanoalloys of Group 11 (Cu, Ag, Au) 865 5.1.1. Cu−Ag 866 5.1.2. Cu−Au 867 5.1.3. Ag−Au 870 5.1.4. Cu−Ag−Au 872 5.2. Nanoalloys of Group 10 (Ni, Pd, Pt) 872 5.2.1. Ni−Pd 872 * To whom correspondence should be addressed. Phone: +39010 3536214. Fax:+39010 311066. E-mail: ferrando@fisica.unige.it. † Universita di Genova. ‡ Argonne National Laboratory. § University of Birmingham. | As of October 1, 2007, Chemical Sciences and Engineering Division. Volume 108, Number 3

Nanoalloys: From Theory to Applications of Alloy Clusters and Nanoparticles

The recent advances in electrocatalysis for oxygen reduction reaction (ORR) for proton exchange membrane fuel cells (PEMFCs) are thoroughly reviewed. This comprehensive Review focuses on the low- and non-platinum electrocatalysts including advanced platinum alloys, core–shell structures, palladium-based catalysts, metal oxides and chalcogenides, carbon-based non-noble metal catalysts, and metal-free catalysts. The recent development of ORR electrocatalysts with novel structures and compositions is highlighted. The understandings of the correlation between the activity and the shape, size, composition, and synthesis method are summarized. For the carbon-based materials, their performance and stability in fuel cells and comparisons with those of platinum are documented. The research directions as well as perspectives on the further development of more active and less expensive electrocatalysts are provided.

http://repository.ust.hk/ir/bitstream/1783.1-77094/1/acs.chemrev.5b00462_withlink.pdf

Recent Advances in Electrocatalysts for Oxygen Reduction Reaction

Dealloying is a common corrosion process during which an alloy is 'parted' by the selective dissolution of the most electrochemically active of its elements. This process results in the formation of a nanoporous sponge composed almost entirely of the more noble alloy constituents. Although considerable attention has been devoted to the morphological aspects of the dealloying process, its underlying physical mechanism has remained unclear. Here we propose a continuum model that is fully consistent with experiments and theoretical simulations of alloy dissolution, and demonstrate that nanoporosity in metals is due to an intrinsic dynamical pattern formation process. That is, pores form because the more noble atoms are chemically driven to aggregate into two-dimensional clusters by a phase separation process (spinodal decomposition) at the solid-electrolyte interface, and the surface area continuously increases owing to etching. Together, these processes evolve porosity with a characteristic length scale predicted by our continuum model. We expect that chemically tailored nanoporous gold made by dealloying Ag-Au should be suitable for sensor applications, particularly in a biomaterials context.

/pdf/evolution-of-nanoporosity-in-dealloying-1vysl3gdw0.pdf

Evolution of nanoporosity in dealloying

This paper reexamines the concept of the dealloying critical potential by considering the critical potential to be a kinetically controlled morphological transition dependent not only on extensive system parameters such as alloy and electrolyte composition, but also on the rate of application of an intrinsic parameter such as the potential ramp rate. In the limit of a quasi-static potential sweep rate, an expression for the critical potential is derived which considers both compositional and morphological fluctuations on the alloy surface at the incipient point of either stability (passivation) or instability (bulk dealloying). In addition, we present detailed critical potential results for the entire range of Ag-Au alloy compositions in x M AgClO 4 + 1 M HClO 4 and x M AgNO 3 + 1 M HNO 3 (x = 10 -4 , 10 -3 , 10 -2 10 -1 , and 1). These results are shown to be consistent with the expression for the critical potential. Finally, we present and discuss ancillary experiments examining the effect of potential sweep rate on the determination of the critical potential.

https://iopscience.iop.org/article/10.1149/1.1492288/pdf

The Dealloying Critical Potential

Electrocatalytic activity of spinel related cobalties MxCo3−xO4 (M = Li, Ni, Cu) in the oxygen evolution reaction

Composition-dependent electrocatalytic activity of Pt-Cu nanocube catalysts for formic acid oxidation.

We present results of a comprehensive electrochemical study aimed at determining the factors that control the corrosion evolution of the important structural alloy Al 2024-T3. An important aspect of corrosion in this alloy is copper redistribution. The redistributed copper serves to enhance the kinetics of the corrosion process and presents some major difficulties with respect to development of new families of conversion coatings. Two major sources of mobile copper are discussed, the Al 2 CuMg S-phase and copper in solid solution. In each case, a dealloying mechanism is responsible for liberating copper that becomes available to redistribution by solid state and/or liquid phase transport mechanisms. This work is concerned with identifying the relative importance of these sources of copper and the active transport mechanisms. In order to decouple the sources of copper, we designed synthetic 2024 alloys that emulate the oxygen reduction kinetics of the real alloy. Our results indicate that. in principal, both sources of copper are operative during redistribution and, for the particular alloy that we examined, both contribute about equally to the amount of redistributed copper.

Nikolay Dimitrov

Papers

Evolution of nanoporosity in dealloying

The Dealloying Critical Potential

Electrocatalytic activity of spinel related cobalties MxCo3−xO4 (M = Li, Ni, Cu) in the oxygen evolution reaction

Composition-dependent electrocatalytic activity of Pt-Cu nanocube catalysts for formic acid oxidation.

Dealloying and Corrosion of Al Alloy 2024 T 3

Nikolay Dimitrov

Papers

Evolution of nanoporosity in dealloying

The Dealloying Critical Potential

Electrocatalytic activity of spinel related cobalties MxCo3−xO4 (M = Li, Ni, Cu) in the oxygen evolution reaction

Composition-dependent electrocatalytic activity of Pt-Cu nanocube catalysts for formic acid oxidation.

Dealloying and Corrosion of Al Alloy 2024 ­ T 3

Dealloying and Corrosion of Al Alloy 2024 T 3