No abstract

Nitrogen-doped ordered mesoporous carbon was synthesized using SBA-15 as the template and polypyrrole as the nitrogencontaining carbon precursor. Transmission electron microscopy and N 2 Brunauer, Emmett, and Teller adsorption revealed a honeycomb-like ordered mesoporous structure with an average pore diameter of 3.3 nm with a narrow distribution. X-ray photoelectron spectroscopy showed that pyridinic and quaternary nitrogen functionalities were the dominant nitrogen surface functional groups. A high percentage of nitrogen was retained in the carbon surface ͑C/N = 8.3͒. The prepared nitrogenfunctionalized support had a specific double layer capacitance of 182.5 F/g. Also, its intrinsic oxygen reduction activity was better than that of Vulcan XC-72R. Accelerated degradation test showed that nitrogen-functionalized carbon was highly resistant to electrochemical corrosion.

WO 3 was investigated as a possible support material for monolayer Pt ORR electrocatalysts in acid electrolyte. It was found that as-prepared Pt/WO 3 showed enhanced activity for the ORR and superior electron transfer ability compared to conventional Pt/C and bulk polycrystalline Pt. However, similar to other tungsten derived supports, most notably WC, the Pt/WO 3 electrocatalyst showed significant performance degradation that was tied directly to the formation of water-soluble hydrogen tungsten bronze (H x WO 3 ) on the support surface that was identified by Xray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM). This information, combined with previous work by our group on WC supports, are also combined to propose a series degradation pathway for WC and WO 3 supports in acid media, which is relevant for proton exchange membrane (PEM) fuel cells.

The activity and the durability of Pt based electrocatalysts constitute the major challenges in the current fuel cell technology. Motivated by the improved activity and ameliorated durability for Pt based cathode catalysts achieved from the compositional and morphological control, respectively, in this paper, a rationally designed, PtCu based, 1-dimensional electrocatalyst was prepared via a facile and scalable procedure. The detailed materials characterization revealed that the as-prepared nanotubes (NTs) were composed of a PtCu alloy bulk and a Pt-enriched surface with downshifted d-band center position.Towards the electrocatalysis of oxygen reduction reaction, PtCu NTs have displayed a distinguished specific activity with more than a 10-fold improvement relative to the commercial catalysts and more than a 3-fold improvement relative to the 2015 DOE technical target (0.72 mA cm Pt À2 @ 0.9 V).Meanwhile, PtCu NTs have shown greatly ameliorated durability in the aspects of both ECSA and mass activity compared to Pt/C (40%) and Pt black after a 6000-cycle accelerated durability test.

The leading cause for safety vent rupture in alkaline batteries is the intrinsic instability of Zn in the highly alkaline reacting environment. Zn and aqueous KOH react in a parasitic process to generate hydrogen gas, which can rupture the seal and vent the hydrogen along with small amounts of electrolyte, and thus, damage consumer devices. Abusive conditions, particularly deep discharge, are known to accelerate this "gassing" phenomena. In order to understand the fundamental drivers and mechanisms for such gassing behavior, the results from multiphysics modeling, ex-situ microscopy and operando measurements of cell potential, pressure and visualization have been combined. Operando measurements were enabled by the development a new research platform that enables a cross-sectional view of a cylindrical Zn-MnO 2 primary alkaline battery throughout its discharge and recovery. A second version of this cell can actively measure the in-cell pressure during the discharge. It is shown that steep concentration gradients emerge during the cell discharge through a redox electrolyte mechanism, leading to the formation of high surface area Zn deposits that experience rapid corrosion when the cell rests to its open circuit voltage. Such corrosion is paired with the release of hydrogen and high cell pressure -eventually leading to cell rupture.