The rising interest in fuel cell vehicle technology (FCV) has engendered a growing need and realization to develop rational chemical strategies to create highly efficient, durable, and cost-effective fuel cells. Specifically, technical limitations associated with the major constituent components of the basic proton exchange membrane fuel cell (PEMFC), namely the cathode catalyst and the proton exchange membrane (PEM), have proven to be particularly demanding to overcome. Therefore, research trends within the community in recent years have focused on (i) accelerating the sluggish kinetics of the catalyst at the cathode and (ii) minimizing overall Pt content, while simultaneously (a) maximizing activity and durability as well as (b) increasing membrane proton conductivity without causing any concomitant loss in either stability or as a result of damage due to flooding. In this light, as an example, high temperature PEMFCs offer a promising avenue to improve the overall efficiency and marketability of fuel cell technology. In this Critical Review, recent advances in optimizing both cathode materials and PEMs as well as the future and peculiar challenges associated with each of these systems will be discussed.

We have synthesized novel ultrathin ternary PtRuFe nanowires (NW) and probed both their methanol oxidation reaction (MOR) and formic acid oxidation reaction (FAOR) activities as a function of chemical composition.

Fibers seen in a new light? Inorganic–organic heterostructured cylindrical waveguides are prepared by a one‐step electrospinning approach, where the photoluminescence from semiconductor quantum dots embedded in a fiber acts as an internal light source. Subwavelength‐sized nanofibers (see image) with a length of several micrometers act as waveguides. Integrating such structures with Si‐based microelectronics to realize nanoscale optoelectronics is envisaged.

Despite increasing interest in the use of one-dimensional (1D) noble metal nanostructures for the oxygen reduction reaction, there has been a surprising lack of effort expended in thoroughly and rationally examining the influence of various physicochemical properties of 1D electrocatalysts with respect to their intrinsic performance. In this Perspective, we address this important issue by investigating and summarizing recent theoretical and experimental progress aimed at precisely deducing the nature of the complex interplay among size, chemical composition, and electrocatalytic performance in high-quality elemental and bimetallic 1D noble metal nanowire systems. In terms of these structural parameters, significant enhancements in both activity and durability of up to an order of magnitude in the case of Pt–Pd1–x Au x nanowires, for example, can be achieved by rationally tuning both wire size and composition. The fundamental insights acquired are then utilized to discuss future and potentially radically new directions toward the continuous improvement and optimization of 1D catalysts.

An ambient, surfactant-based synthetic means was used to prepare ultrathin binary (d ∼ 2 nm) Pd−Ni nanowires, which were subsequently purified using a novel butylamine-based surfactant-exchange process coupled with an electrochemical CO adsorption and stripping treatment to expose active surface sites. We were able to systematically vary the chemical composition of as-prepared Pd−Ni nanowires from pure elemental Pd to Pd 0.50 Ni 0.50 (atomic ratio), as verified using EDS analysis. The overall morphology of samples possessing >60 atom % Pd consisted of individual, discrete one-dimensional nanowires. The electrocatalytic performances of elemental Pd, Pd 0.90 Ni 0.10 , Pd 0.83 Ni 0.17 , and Pd 0.75 Ni 0.25 nanowires in particular were examined. Our results highlight a "volcano"-type relationship between chemical composition and corresponding ORR activities with Pd 0.90 Ni 0.10 , yielding the highest activity (i.e., 1.96 mA/cm 2 at 0.8 V) among all nanowires tested. Moreover, the Pd 0.90 Ni 0.10 sample exhibited outstanding methanol tolerance ability. In essence, there was only a relatively minimal 15% loss in the specific activity in the presence of 4 mM methanol, which was significantly better than analogous data on Pt nanoparticles and Pt nanowires. In addition, we also studied ultrathin, core−shell Pt∼Pd 0.90 Ni 0.10 nanowires, which exhibited a specific activity of 0.62 mA/cm 2 and a corresponding mass activity of 1.44 A/mg Pt at 0.9 V. Moreover, our as-prepared core−shell electrocatalysts maintained excellent electrochemical durability. We postulate that one-dimensional Pd−Ni nanostructures represent a particularly promising platform for designing ORR catalysts with high performance.

Developing novel electrocatalysts for small molecule oxidation processes, including formic acid oxidation (FAOR), methanol oxidation reaction (MOR), and ethanol oxidation reaction (EOR), denoting the key anodic reactions for their respective fuel cell configurations, is a significant and relevant theme of recent efforts in the field. Herein, in this report, we demonstrated a concerted effort to couple and combine the benefits of small size, anisotropic morphology, and tunable chemical composition in order to devise a novel "family" of functional architectures. In particular, we have fabricated not only ultrathin 1-D Pd(1-x)Cu(x) alloys but also Pt-coated Pd(1-x)Cu(x) (i.e., Pt∼Pd(1-x)Cu(x); herein the ∼ indicates an intimate association, but not necessarily actual bond formation, between the inner bimetallic core and the Pt outer shell) core-shell hierarchical nanostructures with readily tunable chemical compositions by utilizing a facile, surfactant-based, wet chemical synthesis coupled with a Cu underpotential deposition technique. Our main finding is that our series of as-prepared nanowires are functionally flexible. More precisely, we demonstrate that various examples within this "family" of structural motifs can be tailored for exceptional activity with all 3 of these important electrocatalytic reactions. In particular, we note that our series of Pd(1-x)Cu(x) nanowires all exhibit enhanced FAOR activities as compared with not only analogous Pd ultrathin nanowires but also commercial Pt and Pd standards, with Pd9Cu representing the "optimal" composition. Moreover, our group of Pt∼Pd(1-x)Cu(x) nanowires consistently outperformed not only commercial Pt NPs but also ultrathin Pt nanowires by several fold orders of magnitude for both the MOR and EOR reactions in alkaline media. The variation of the MOR and EOR performance with the chemical composition of our ultrathin Pt∼Pd(1-x)Cu(x) nanowires was also discussed.

One means of combining the unique physical and chemical properties of both carbon nanotubes and complementary material motifs (such as metal sulfide quantum dots (QDs), metal oxide nanostructures, and polymers) can be achieved by generating carbon nanotube (CNT)-based heterostructures. These materials can be subsequently utilized as novel and interesting constituent building blocks for the assembly of functional light energy harvesting devices and because of their architectural and functional flexibility, can potentially open up novel means of using and taking advantage of existing renewable energy sources. In this review, we present the reliable and reproducible synthesis of several unique model CNT-based heterostructured systems as well as include an accompanying discussion about the charge transfer and energy flow properties of these materials for their potential incorporation into a range of practical solar energy conversion devices.

The oxygen evolution reaction (OER) is a key reaction for water electrolysis cells and air-powered battery applications. However, conventional metal oxide catalysts, used for high-performing OER, tend to incorporate comparatively expensive and less abundant precious metals such as Ru and Ir, and, moreover, suffer from poor stability. To attempt to mitigate for all of these issues, we have prepared one-dimensional (1D) OER-active perovskite nanorods using a unique, simple, generalizable, and robust method. Significantly, our work demonstrates the feasibility of a novel electroless, seedless, surfactant-free, wet solution-based protocol for fabricating "high aspect ratio" LaNiO and LaMnO nanostructures. As the main focus of our demonstration of principle, we prepared as-synthesized LaNiO rods and correlated the various temperatures at which these materials were annealed with their resulting OER performance. We observed generally better OER performance for samples prepared with lower annealing temperatures. Specifically, when annealed at 600 °C, in the absence of a conventional conductive carbon support, our as-synthesized LaNiO rods not only evinced (i) a reasonable level of activity toward OER but also displayed (ii) an improved stability, as demonstrated by chronoamperometric measurements, especially when compared with a control sample of commercially available (and more expensive) RuO.