With the approaching commercialization of PEM fuel cell technology, developing active, inexpensive non-precious metal ORR catalyst materials to replace currently used Pt-based catalysts is a necessary and essential requirement in order to reduce the overall system cost. This review paper highlights the progress made over the past 40 years with a detailed discussion of recent works in the area of non-precious metal electrocatalysts for oxygen reduction reaction, a necessary reaction at the PEM fuel cell cathode. Several important kinds of unsupported or carbon supported non-precious metal electrocatalysts for ORR are reviewed, including non-pyrolyzed and pyrolyzed transition metal nitrogen-containing complexes, conductive polymer-based catalysts, transition metal chalcogenides, metal oxides/carbides/nitrides/oxynitrides/carbonitrides, and enzymatic compounds. Among these candidates, pyrolyzed transition metal nitrogen-containing complexes supported on carbon materials (M–N_x /C) are considered the most promising ORR catalysts because they have demonstrated some ORR activity and stability close to that of commercially available Pt/C catalysts. Although great progress has been achieved in this area of research and development, there are still some challenges in both their ORR activity and stability. Regarding the ORR activity, the actual volumetric activity of the most active non-precious metal catalyst is still well below the DOE 2015 target. Regarding the ORR stability, stability tests are generally run at low current densities or low power levels, and the lifetime is far shorter than targets set by DOE. Therefore, improving both the ORR activity and stability are the major short and long term focuses of non-precious metal catalyst research and development. Based on the results achieved in this area, several future research directions are also proposed and discussed in this paper.

Lithium-ion batteries (LIBs) are currently the most suitable energy storage device for powering electric vehicles (EVs) owing to their attractive properties including high energy efficiency, lack of memory effect, long cycle life, high energy density and high power density. These advantages allow them to be smaller and lighter than other conventional rechargeable batteries such as lead–acid batteries, nickel–cadmium batteries (Ni–Cd) and nickel–metal hydride batteries (Ni–MH). Modern EVs, however, still suffer from performance barriers (range, charging rate, lifetime, etc.) and technological barriers (high cost, safety, reliability, etc.), limiting their widespread adoption. Given these facts, this review sets the extensive market penetration of LIB-powered EVs as an ultimate objective and then discusses recent advances and challenges of electric automobiles, mainly focusing on critical element resources, present and future EV markets, and the cost and performance of LIBs. Finally, novel battery chemistries and technologies including high-energy electrode materials and all-solid-state batteries are also evaluated for their potential capabilities in next-generation long-range EVs.

This paper gives a comprehensive review about the most recent progress in synthesis, characterization, fundamental understanding, and the performance of graphene and graphene oxide sponges. Practical applications are considered including use in composite materials, as the electrode materials for electrochemical sensors, as absorbers for both gases and liquids, and as electrode materials for devices involved in electrochemical energy storage and conversion. Several advantages of both graphene and graphene oxide sponges such as three dimensional graphene networks, high surface area, high electro/thermo conductivities, high chemical/electrochemical stability, high flexibility and elasticity, and extremely high surface hydrophobicity are emphasized. To facilitate further research and development, the technical challenges are discussed, and several future research directions are also suggested in this paper.