We propose guidelines for the design of improved bimetallic (and related) electrocatalysts for the oxygen reduction reaction (ORR) in acidic media. This guide is based on simple thermodynamic principles assuming a simple mechanism where one metal breaks the oxygen-oxygen bond of molecular O(2) and the other metal acts to reduce the resulting adsorbed atomic oxygen. Analysis of the Gibbs free energies of these two reactions guides the selection of combinations of metals that can produce alloy surfaces with enhanced activity for the ORR when compared to the constituent metals. Selected systems have been tested by fabricating arrays of metallic catalysts consisting of various binary and ternary combinations of Pd, Au, Ag, and Co deposited on glassy carbon (GC) substrates. The electrocatalytic activity of these materials for the ORR in acidic medium was examined using scanning electrochemical microscopy (SECM) in a new rapid-imaging mode. This was used to rapidly screen arrays covering a wide range of catalyst compositions for their activity for the ORR in 0.5 M H(2)SO(4). Using the SECM technique, we have identified combinations of metals with enhanced electrocatalytic activities when compared with the constituent, pure metals. Addition of Co to Pd, Au, and Ag clearly decreases the ORR overpotential, in agreement with the proposed model. Catalyst spots that exhibited enhanced electrocatalytic activity in the SECM screening technique were then examined using classical rotating disk electrode (RDE) experiments. The activity of carbon black supported catalyst mixtures on a GC RDE and the electrocatalytic activity determined using the SECM screening technique showed excellent agreement. C/Pd-Co electrodes (10-30% Co) exhibited remarkable activity for ORR catalysis, close to that of carbon-supported Pt.

Activated carbons from biomass (grass and Camellia japonica) exhibit enhanced CO2 uptake at 25 °C; up to 1.5 mmol g−1 at 0.15 bar, 5.0 mmol g−1 at 1 bar and 21.1 mmol g−1 at 20 bar, and depending on level of activation, have excellent uptake at both low (≤1 bar) and high (20 bar) pressure.

The development of next‐generation molecular‐electronic, electrocatalytic, and energy‐storage systems depends on the availability of robust materials in which molecular charge‐storage sites and conductive hosts are in intimate contact. It is shown here that electron transfer from single‐walled carbon nanotubes (SWNTs) to polyoxometalate (POM) clusters results in the spontaneous formation of host–guest POM@SWNT redox‐active hybrid materials. The SWNTs can conduct charge to and from the encapsulated guest molecules, allowing electrical access to >90% of the encapsulated redox species. Furthermore, the SWNT hosts provide a physical barrier, protecting the POMs from chemical degradation during charging/discharging and facilitating efficient electron transfer throughout the composite, even in electrolytes that usually destroy POMs.

Batteries that extend performance beyond the intrinsic limits of Li-ion batteries are among the most important developments required to continue the revolution promised by electrochemical devices. Of these next-generation batteries, lithium sulfur (Li–S) chemistry is among the most commercially mature, with cells offering a substantial increase in gravimetric energy density, reduced costs and improved safety prospects. However, there remain outstanding issues to advance the commercial prospects of the technology and benefit from the economies of scale felt by Li-ion cells, including improving both the rate performance and longevity of cells. To address these challenges, the Faraday Institution, the UK’s independent institute for electrochemical energy storage science and technology, launched the Lithium Sulfur Technology Accelerator (LiSTAR) programme in October 2019. This Roadmap, authored by researchers and partners of the LiSTAR programme, is intended to highlight the outstanding issues that must be addressed and provide an insight into the pathways towards solving them adopted by the LiSTAR consortium. In compiling this Roadmap we hope to aid the development of the wider Li–S research community, providing a guide for academia, industry, government and funding agencies in this important and rapidly developing research space.

Porous nanocomposites consisting of cellulose nanocrystals (CNXLs) and polypyrrole (PPY) were fabricated using electrochemical co-deposition. The CNXLs were extracted from cotton using sulfuric acid hydrolysis and were subjected to 2,2,6,6-tetramethylpiperidine-1-oxyl-mediated oxidation, in which primary hydroxyls were oxidized to carboxylate moieties. The PPY/CNXL composites were electrodeposited from a solution of the carboxylated CNXLs and pyrrole (PY) monomers, and the negatively charged CNXLs were incorporated as the counteranion during electrodeposition. The resulting PPY/CNXL nanocomposites were characterized using scanning electron microscopy, cyclic voltammetry, and electrochemical impedance spectroscopy (EIS). Cyclic voltammetry and EIS analysis of the PPY/CNXL nanocomposites showed that the stability and specific capacitance of the nanocomposite material were higher than that of PPY containing Cl− anions. The electrochemical performance of the PPY/CNXL nanocomposites was also compared to that of a PPY/carbon nanotube (CNT) composite deposited under the same conditions, which revealed that the PPY/CNXL nanocomposites had a capacitance similar to that of the PPY/CNT nanocomposite and was at least equally as stable as the PPY/CNT nanocomposite.

H 2 oxidation and O 2 reduction have been studied as a function of temperature at Pt electrodes in the protic ionic liquid diethylmethylammonium trifluoromethanesulfonate. Hydrodynamic voltammetry showed that the H 2 oxidation reaction (HOR) became hindered at positive potentials (>1.0 V). Electrochemical analysis and X-ray photoelectron spectroscopy revealed that this drop in HOR activity was due to the formation of an adsorbed blocking oxide layer, which formed on the Pt surface due to trace H 2 O oxidation at positive potentials. Electrochemical analysis also revealed that the O 2 reduction reaction (ORR) occurred at an appreciable rate only when pre-existing surface oxides were reduced. As the temperature increased, the potential at which the surface oxides were reduced shifted to more positive potentials and the reduction peak narrowed. The net result was significantly higher rates of the ORR at positive potentials at higher temperatures. Finally, even when Pt surfaces were not initially covered with an oxide adlayer, the rate of the ORR increased significantly upon increasing the temperature and some possible reasons for this temperature dependence are discussed.

Additional bimetallic electrocatalysts for the oxygen reduction reaction ͑ORR͒ in acidic media were designed using a previously reported thermodynamic selection guide. The electrocatalyst mixtures were prepared in large arrays on glassy carbon substrates and the electrocatalytic activity was screened using scanning electrochemical microscopy ͑SECM͒. Activities were measured for a range of bimetallic combinations that showed a synergetic electrocatalytic effect during screening, including Au-V, Ag-V, Pd-Mn, and Pd-V. Upon initial screening, a highly active electrocatalytic combination consisting of 60:40 Pd-V was identified. Using rotating disk electrode ͑RDE͒ experiments, the high activity of this combination for the ORR in acidic media was confirmed when the electrocatalysts were supported on Vulcan carbon. The electrocatalytic activity of Pd-V was close to that exhibited by Pt, the electrocatalyst of choice for the ORR in acidic media, and thus is another example of a nonplatinum catalyst with high activity that follows the previous strategy for catalyst design.

In this Tutorial Review, we describe the critical role redox active molecular species are playing in the development of the next generation of “beyond-lithium ion” battery technologies.