Geopolymer Based Electrodes as New Class of Material for Electrochemical CO2 Reduction

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Geopolymer Based Electrodes as New Class of Material for Electrochemical CO2 Reduction

Geoploymers for CO2 reduction: Geoploymers offer great potential for reducing CO2 emissions in the construction sector by replacing ordinary cement. Here, we successfully functionalized a geopolymer with tin and applied the hybrid material as an electrode for CO2 electrolysis. The results show current efficiencies of up to 14 % for formate production.


Abstract

To achieve a successful transition to a sustainable carbon and energy management, it is essential to both reduce CO2 emissions and develop new technologies that utilize CO2 as a starting substrate. In this study, we demonstrate for the first-time the functionalization of geopolymer binder (GP) with Sn for electrochemical CO2 reduction (eCO2RR) to formate. By substituting cement with Sn-GP, we have merged CO2 utilisation and emission reduction. Using a simple mixing procedure, we were able to obtain a pourable mortar containing 5 vol. % Sn-powder. After hardening, the Sn-GP electrodes were characterized for their mechanical and CO2 electrolysis performance. In 10 h electrolyses, formate concentrations were as high as 22.7±0.9 mmol L−1 with a corresponding current efficiency of 14.0±0.5 % at a current density of 20 mA cm−2. Our study demonstrates the successful design of GP-electrodes as a new class of hybrid materials that connect eCO2RR and construction materials.

Application of Naphthoquinone Derivatives Non‐Covalently Modified Graphene Nanosheets in Asymmetric Supercapacitors

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Application of Naphthoquinone Derivatives Non-Covalently Modified Graphene Nanosheets in Asymmetric Supercapacitors


Abstract

As an organic pseudocapacitive active material, 2, 3-Dichloro-1, 4-naphthoquinone (DNQ) was used in supercapacitors. Graphene with unique structures and high electrical conductivity acts as substrate. DNQ non-covalently modified graphene composite material (DNQ@rGO) was synthesized through the simple solvothermal synthesis. The redox reaction between naphthol and naphthoquinone occurs on reduced graphene oxide(rGO), which forms an ideal pseudocapacitance without destroying its sp 2 network. The optimal DNQ@rGO electrode material obtained the specific capacitance of 361.2 Fg−1 at 5 mV s−1 in 1 mol L−1 H2SO4 and exhibited excellent rate capability (capacitance retention of 87.5 % at 100 mV s−1) in the three-electrode system. We also prepared holey layered oxygen-rich graphene hydrogels (HLGH) material, whose electrochemical performance is superior to traditional three-dimensional (3D) graphene hydrogels (GH). Finally, two asymmetric supercapacitors (ASCs) were assembled by using the DNQ@rGO (positive electrode), the HLGH and GH (negative electrode). The results show that the ASC with HLGH as negative electrode achieved the high energy and power densities due to the perfect matching of capacitance and kinetics between the positive and negative electrodes. The specific capacitance was almost no loss after 4700 cycles, showing the excellent stability.