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Poly(p-phenylene)-based ionomers with remarkable durability and rate capability for use in vanadium redox flow batteries (VRFBs) are reported. The family of synthesized ionomers, sPBPSP-z, exhibited not only well-developed phase separation between hydrophilic domains and hydrophobic domains but also well-connected hydrophilic channels, resulting in enhanced proton conductivities and excellent dimensional stabilities. sPBPSP-8, which has an ion exchange capacity of 1.83 meq g−1, showed high discharge capacity retention and superior efficiencies over 100 cycles at a current density of 50 mA cm−2. In addition, the sPBPSP-8 ionomer exhibited stable performance at various current densities (50–180 mA cm−2) and retained high efficiencies at high current densities. Furthermore, this material exhibited superior chemical stability under oxidizing conditions, excellent capacity retention, and high efficiencies during long-term VRFB operation (1000 cycles). These results indicate that the sPBPSP-8 membrane is a superb material for VRFB applications.

A new facile template-free method is presented to synthesize Fe-treated N-doped carbon (Fe/N–C) catalysts for oxygen reduction reaction (ORR) by employing a synthesis protocol of pyrolysis–leaching–stabilization (PLS) sequence of polypyrrole in the presence of ferric source, which serves dual purposes of an oxidant for pyrrole polymerization and an iron source. Each step in the PLS sequence is assessed in detail in terms of the related structural properties of the resulting carbon catalysts, and their effects on ORR activities are elaborated to confirm the validity of the current synthesis protocol. It is found that the as-prepared carbon catalyst exhibits outstanding high catalytic activity in both alkaline and acidic conditions. The carbon catalyst prepared at a pyrolysis temperature of 900 °C (FePPyC-900) shows remarkably high ORR activity with onset potential of 0.96 V (vs. RHE), which is similar to that of Pt/C, whereas the half-wave potential (E1/2) of FePPyC-900 is 0.877 V, more positive than that of Pt/C at the same catalyst loading amount under alkaline conditions. Furthermore, the FePPyC-900 catalyst also illustrates exceptionally high activity under acidic conditions with onset and half-wave potentials of 0.814 and 0.740 V, respectively, which are almost comparable to those (0.817 and 0.709 V) of the state-of-the-art Pt/C catalyst, which is rarely observed for non-Pt-based carbon catalysts. In addition, the FePPyC-900 catalyst displays much better stability and methanol tolerance than the Pt/C and exhibits a four electron transfer pathway under both alkaline and acidic conditions. Such extraordinary high ORR activity and stability of the FePPyC-samples can be attributed to the implementation of extra stabilization step in addition to conventional sample preparation steps of pyrolysis and subsequent leaching in current PLS synthesis protocol as well as to the use of highly conducting PPy as a single precursor of carbon and nitrogen in the presence of Fe.

It has been considered that the presence of Fe-N in the carbon network helps to enhance oxygen reduction reaction (ORR) activity of the carbon. In this study, N-doped platelet ordered mesoporous carbon is prepared using Fe-phthalocyanine as a single precursor for nitrogen, iron and carbon sources. We show that the physical presence of Fe is not necessary to enhance the ORR activity of N-doped carbon, although Fe is required to create more active sites and to increase the electrical conductivity in the carbon framework.

A simple binder-free synthesis approach of just rubbing nitrogen-doped reduced graphene oxide (N-RGO) powder on a mechanically grinded Cu-foil substrate with a rough surface is proposed for a lithium ion battery (LIB). The nitrogen content of N-RGO is found to be 2.1 wt%. The binder-free N-RGO electrode shows excellent reversible capacity of 551 mA h g−1 as compared to 433 mA h g−1 of the binder-added N-RGO electrode at a current density of 50 mA g−1 after 100 cycles. The process is not only highly reproducible and successful, but also results in high LIB performance, proposing easy scaling-up of such an electrode for commercial application.

Hollow core–mesoporous shell carbon (HCMSC) with hierarchical nanoarchitecture was prepared and explored as an anode with ultra-high Li storage capacity in Li ion batteries. Compared with commercial graphite and ordered mesoporous carbon (CMK-3), the HCMSC not only demonstrates higher Li storage capacity, but also better cycling performance and rate capability. HCMSC possesses unique structural characteristics such as large surface area and mesopore volume. Particularly the hierarchical macro-scaled hollow core/mesoporous shell nanostructure along with 3D large interconnected interstitial volume guarantees fast mass transport in HCMSC, resulting in ultra-high Li storage capacity and excellent cycling performance and rate capability. Furthermore, the hollow macro-scaled core encapsulated in a well-developed 3D interconnected mesoporous shell serves as an efficient Li storage and buffer reservoir to reduce volume change during the charge–discharge cycling especially at high rates, which contributes greatly to the enhanced cycling performance and rate capability.