Force-responsive ordered carbonaceous frameworks synthesized from Ni-porphyrin.

Force-responsive ordered carbonaceous frameworks (OCFs) are synthesized for the first time. Carbonization of Ni porphyrin monomers having eight polymerizable ethynyl groups yields OCFs with atomically dispersed divalent Ni species and developed micropores. The highest specific surface area (673 m2 g-1) among the OCFs has been achieved. The OCFs thus synthesized comprise non-stacked graphene sheets, affording a unique mechanical flexibility that enables force-driven reversible phase transition.

The electrochemistry of size dependent graphene via liquid phase exfoliation: capacitance and ionic transport.

Recently, graphene-based materials have become ubiquitous in electrochemical devices including electrochemical sensors, electrocatalysts, capacitive and membrane desalination and energy storage devices. However, many of the electrochemical properties of graphene (particularly the capacitance and ionic transport) are not yet fully understood. This paper explores the capacitance and ionic transport properties of size dependent graphene (from 100 nm to 1 µm) prepared through the liquid phase exfoliation of graphite in which the size of graphene was finely selected using a multi-step centrifugation technique. Our experiment was then expanded to include basal plane graphene using highly ordered pyrolytic graphite as a model electrode, describing the assumed theoretical graphene capacitance (quoted as 550 F g-1 or 21 µF cm-2) and the electrochemical surface area of the carbon-based materials. This work improves our understanding of graphene electrochemistry (capacitance and ion transport), which should lead to the continuing development of many high-performance electrochemical devices, especially supercapacitors, capacitive desalination and ion-based selective membranes.

Controlling the flake size of bifunctional 2D WSe2 nanosheets as flexible binders and supercapacitor materials.

A new approach using graphene as a conductive binder in electrical supercapacitors has recently been proposed. Graphene shows outstanding properties as a conductive binder, and can be used to replace conductive, additive, and polymer binders. However, graphene follows an EDLC behaviour, which may limit its electrochemical performance. In the process described in this work, we introduced WSe2 nanoflakes as a new approach to using pseudocapacitive materials as binders. The WSe2 nanoflakes were produced through liquid phase exfoliation of bulk WSe2, and the flake size was finely selected using a controlled centrifugation speed. The physical and electrochemical properties of the exfoliated WSe2 flakes were analysed; it was found that the smallest flakes (an average flake size of 106 nm) showed outstanding electrochemical properties, expanding our understanding of transition metal dichalcogenide (TMD) materials, and we were able to demonstrate the applicability of using WSe2 as a binder in supercapacitor electrodes. We also successfully replaced conductive additives and polymer binders with WSe2. The overall performance was improved: capacitance was enhanced by 35%, charge transfer resistance reduced by 73%, and self-discharge potential improved by 9%. This study provides an alternative application of using TMD materials as pseudo capacitive binders, which should lead to the continued development of energy storage technology.

Enhancing the Dispersion of Cu-Ni Metals on the Graphene Aerogel Support for Use as a Catalyst in the Direct Synthesis of Dimethyl Carbonate from Carbon Dioxide and Methanol.

Graphene has attracted attention because of its interesting properties in catalyst applications including as a catalyst support; however, it is known that the graphene can be restacked, forming a graphite-like structure that leads to poor specific surface area. Hence, the high-porosity graphene aerogel was used as a Cu-Ni catalyst support to produce dimethyl carbonate (DMC) from carbon dioxide and methanol. In this work, we have introduced a new synthesis route, which can improve the dispersion of metal particles on the graphene aerogel support. Cu-Ni/graphene aerogel catalysts were synthesized by a two-step procedure: forming Cu-Ni/graphene aerogel catalysts via hydrothermal reduction and then Cu-Ni loading by incipient wetness impregnation. It is found that the catalyst prepared by the two-step procedure exhibits higher DMC yield (25%) and MeOH conversion (18.5%) than those of Cu-Ni loading only by an incipient wetness impregnation method. The results prove that this new synthesis route can improve the performance of Cu-Ni/graphene aerogel catalysts for DMC production.