No abstract

Currently, Pt-based electrocatalysts are adopted in the practical proton exchange membrane fuel cell (PEMFC), which converts the energy stored in hydrogen and oxygen into electrical power. However, the broad implementation of the PEMFC, like replacing the internal combustion engine in present automobile fleet, sets a requirement for less Pt loading compared to current devices. In principle, the requirement needs the Pt-based catalyst to be more active and stable. Two main strategies, engineering electronic (d-band) structure (including controlling surface facet, tuning surface composition, and engineering surface strain) and optimizing reactant adsorption sites are discussed and categorized based on the fundamental working principle. In addition, general routes for improving the electrochemical surface area, which improves activity normalized by the unit mass of precious group metal/platinum group metal, and stability of the electrocatalyst are also discussed. Furthermore, the recent progress of This article is protected by copyright. All rights reserved. 2full fuel cell tests of novel electrocatalysts is summarized. It is suggested that a better understanding of the reactant/intermediate adsorption, electron transfer, and desorption occurring at the electrolyte-electrode interface is necessary to fully comprehend these electrified surface reactions; and standardized MEA testing protocols should be practiced, and data with full parameters detailed, for reliable evaluation of catalyst functions in devices.

Hydrogen holds the potential of replacing nonrenewable fossil fuel. Improving the efficiency of hydrogen evolution reaction (HER) is critical for environmental friendly hydrogen generation through electrochemical or photoelectrochemical water splitting. Here we report the surface-engineered PtNi-O nanoparticles with enriched NiO/PtNi interface on surface. Notably, PtNi-O/C showed a mass activity of 7.23 mA/μg at an overpotential of 70 mV, which is 7.9 times higher compared to that of the commercial Pt/C, representing the highest reported mass activity for HER in alkaline conditions. The HER overpotential can be lowered to 39.8 mV at 10 mA/cm when platinum loading was only 5.1 μg/cm, showing exceptional HER efficiency. Meanwhile, the prepared PtNi-O/C nanostructures demonstrated significantly improved stability as well as high current performance which are well over those of the commercial Pt/C and demonstrated capability of scaled hydrogen generation.

A novel CO 2 -selective membrane with the facilitated transport mechanism has been synthesized to capture CO 2 from the industrial gas mixtures, including flue gas. Both mobile and fixed amine carriers were incorporated into the cross-linked poly(vinyl alcohol) (PVA) during the membrane synthesis. The membrane showed desirable CO 2 permeability (with a suitable effective thickness) and CO 2 /N 2 selectivity up to 170 °C. In the CO 2 capture experiments from a gas mixture with N 2 and H 2 , a permeate CO 2 dry concentration of >98% was obtained, using steam as the sweep gas. The effects of the feed flow rate and the sweep:feed molar ratio on the membrane separation performance were investigated. A one-dimensional isothermal model was established to examine the performance of a hollow-fiber membrane module composed of the described CO 2selective membrane. The modeling results show that a CO 2 recovery of >95% and a permeate CO 2 dry concentration of >98% are achievable from a 1000 standard cubic feet per minute (SCFM) (or 21.06 mol/s) flue gas stream with a 2 ft (0.61 m) hollow-fiber module that contained 980 000 fibers.

Silver in the linings The bacterium Shewanella oneidensis is well known to use extracellular electron sinks, metal oxides and ions in nature or electrodes when cultured in a fuel cell, to power the catabolism of organic material. However, the power density of microbial fuel cells has been limited by various factors that are mostly related to connecting the microbes to the anode. Cao et al . found that a reduced graphene oxide–silver nanoparticle anode circumvents some of these issues, providing a substantial increase in current and power density (see the Perspective by Gaffney and Minteer). Electron microscopy revealed silver nanoparticles embedded or attached to the outer cell membrane, possibly facilitating electron transfer from internal electron carriers to the anode. —MAF

No abstract

No abstract

Direct methanol/ethanol alkaline fuel cells (DMAFCs/DEAFCs) represent an attractive mobile power generation technology. The methanol/ethanol oxidation reaction (MOR/EOR) often requires high-performance yet expensive Pt-based catalysts that may be easily poisoned. Herein, we report the development of PtCuNi tetrahedra electrocatalysts with optimized specific activity and mass activity for MOR and EOR. Our synthetic and structural characterizations show that these PtCuNi tetrahedra have Curich core and PtNi-rich shell with tunable surface composition. Electrocatalytic studies demonstrate that Pt 56 Cu 28 Ni 16 exhibits exceptional MOR and EOR specific activities of 14.0 ± 1.0 mA/cm 2 and 11.2 ± 1.0 mA/cm 2 , respectively and record high mass activity of 7.0 ± 0.5 A/mg Pt and 5.6 ± 0.6 A/mg Pt , comparing favorably with the best MOR or EOR Pt alloy-based catalysts reported to date. Furthermore, we show that the unique core−shell tetrahedra configuration can also lead to considerably improved durability.