Direct solar-driven reduction of greenhouse gases into hydrocarbon fuels incorporating thermochemical energy storage via modified calcium looping

The Energy and Environment issue, so called E2E, has become an increasingly severe challenge to our society. The carbon neutrality target before the middle of this century requires an accelerated global transformation towards renewables and sustainable low carbon technologies. Since greenhouse gasses like CO2 and CH4 cause serious climate warming, here we report a modified calcium-looping (CaL) that directly harvest and utilize solar energy to capture and convert CO2 into syngas along with CH4, meanwhile it is accompanied with thermochemical energy storage to overcome the fluctuations of renewable energy. The full advantages of CaL in both carbon capture and utilization and thermal energy storage are taken for establishing such a renewable energy system with near-zero carbon emissions. We dope nanoscale Ni into CaCO3 to enhance the direct solar absorption of the composite material and simultaneously catalyze the in-situ CO2 conversion reaction. The experiment and demonstration of such a CaL are conducted in a fixed bed photo-reactor. The in-situ conversion ratio of CO2 reaches up to 85.6 %, which in reverse facilitates the decomposition of CaCO3. The carbon deposited from the methane decomposition in the calcination process can be eliminated in the subsequent carbonation process. The proposed system achieves negative emissions of greenhouse gas and systematically converts solar energy into hydrocarbon fuel, making it a competitive scheme for clean energy and carbon cycle economy.