Commercial and environmental benefits have made carbon dioxide (CO2) methanation one of the topmost research projects all over the world both at the pilot plant and commercial scale. Mitigation of CO2 via carbon capture and storage (CCS) routes have less motivation from a commercial point of view. Therefore, an integrated system is of paramount importance to convert CO2 into value-added products such as methane (CH4) using solar energy (photosynthesis) or surplus electrical energy in hydrolysis for production of reactant hydrogen to use in CO2 methanation. To date, great efforts have been made to investigate both the reaction mechanism and catalysts development for methanation. Here in this review, up to date references have been cited, which are aimed at giving researchers a comprehensive overview of CO2 methanation with respect to the recent advancements in reaction mechanism, catalytic materials, and the novel combination of metal active phase and its synergy. Both thermochemical and electrochemical routes of CO2 methanation have been discussed, mainly focusing on thermochemical routes. Among the two routes, the thermochemical route seems to be a promising technique for producing an energy carrier due to the high selectivity of CH4.

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Lithium−sulfur batteries can displace lithium-ion batteries owing to their superior theoretical capacity and specific energy density. Presently, however, high specific capacities do not translate to high specific energies, mainly because of the electrolyte excess, which does not meet the required "lean electrolyte" condition. We introduce a separator that requires a minimal amount of electrolyte, 4.5 μL mg −1 , for successful cycling of practical sulfur cathodes. Taking advantage of the self-assembly chemistry of polyelectrolyte complexation, we synthesized a tailored porous nanoparticle, which because of its amphiphilicity, is able to form a submicron coating on the low-surface energy Celgard separator by dip-coating. The tuned pore-size in the range of 1.5−2 nm, abundance of functional groups, and unprecedented adsorption capacity toward LiPS allows the polyelectrolyte complex nanoparticle decorated (PPX) separator to function as an efficient LiPS modulator, while uniquely maintaining lean electrolyte conditions and excellent transport properties. The PPX separator enabled a cell with capacity of 1348 mAh g −1 (5.12 mAh cm −2 ) at 0.2 C. Achieving the challenging trade-off between high capacity and lean electrolyte, we were able to attain high energy density in a pouch cell prototype with an initial capacity of 1218 mAh g −1 and an energy density of 250 Wh kg −1 .