###### Abstract  
Climate warming and environmental problems caused by the excessive consumption of fossil energy and massive CO\({}_{2}\) emissions have seriously damaged the human living environment. This paper develops a new green, efficient, and environmentally friendly CO\({}_{2}\) capture and conversion method, which is a crucial way to alleviate the greenhouse effect. In this study, alkali metal carbonates (and the corresponding hydroxides) are fused and blended to construct a liquid molten salt electrolyte system with excellent performance, which is applied to synthesize carbon materials or carbon-based fuel gas. By regulating the electrolyte composition and electrolysis parameters, carbon-based fuels with different micro-morphologies and compositions can be prepared in a controllable manner. In pure Li\({}_{2}\)CO\({}_{3}\) electrolyte, carbon nanotubes (CNTs) with a high value are synthesized at 750 \({}^{\circ}\)C with, initially, 10 mA/cm\({}^{2}\) and, finally, with 100 mA/cm\({}^{2}\). Carbon spheres are obtained in Li-Ca-Ba at 750 \({}^{\circ}\)C with 200 mA/cm\({}^{2}\), while honeycomb carbon is generated in the electrolyte of Li-Na-K at 450 \({}^{\circ}\)C with 450 mA/cm\({}^{2}\). Syngas (33.6%) or CH\({}_{4}\)-rich fuel gas (40.1%) can also be obtained by adding LiOH into the electrolyte under 500 \({}^{\circ}\)C at 2.0 V and 3.2 V, respectively. This paper provides a new way of utilizing CO\({}_{2}\) resources and a new sustainable green development.  
e 2  
This technique is conducive to transforming CO\({}_{2}\) to carbonic products, but it is subject to the high activity and selectivity catalyst [17]. Furthermore, the high hydrogen consumption also restricts the industrialized process of CO\({}_{2}\) hydrogenation. Similarly, a variety of hydrocarbons can be synthesized via the Fischer-Tropsch reaction (Equation (3)), but the high price of H\({}_{2}\) and CO has become a huge obstacle to further development. [18; 19].  
\[\text{nCO}+(2\text{n}+1)\text{H}_{2}=\text{C}_{\text{n}}\text{H}_{(2\text{n}+2) }+\text{nH}_{2}\text{O} \tag{3}\]  
We demonstrate a new design of the direct synthesis of valuable, carbon-based materials (carbon nanomaterials, methane, and syngas) from ambient CO\({}_{2}\) using eutectic molten salt electrolytes in an alumina reactor. In our study, the broad-based feedstock CO\({}_{2}\) was transformed into high-value, objective products without a noble metal electrocataly at a rate of 100 times faster than that observed in photoelectrochemical systems or fuel cell systems. More importantly, the Fischer-Tropsch reaction was no longer essential to the generation of methane. Syngas or methane can be synthesized via a one-step co-electrolysis of reducible C (from the CO\({}_{3}^{2-}\) in the electrolyte or dissolved CO\({}_{2}\)) and monovalent H (from the OH\({}^{+}\) in the electrolyte or captured H\({}_{2}\)O) in eutectic molten salts. A high-value carbon nanotube content of \(\sim\)80% was observed in the electrolysis of pure Li\({}_{2}\)CO\({}_{3}\) at 750 \({}^{\circ}\)C with increasing current density, starting from 10 mA/cm\({}^{2}\) to 100 mA/cm\({}^{2}\). In the co-electrolysis of the CO\({}_{2}\) and H\({}_{2}\)O system, the CH\({}_{4}\) content can reach 40.1% at 550 \({}^{\circ}\)C under 2.0 V, while the CO content can rise up to 33.6% at 550 \({}^{\circ}\)C under 3.5 V in the electrolyte of Li\({}_{1.43}\)Na\({}_{0.26}\)K\({}_{0.21}\)CO\({}_{3}\) + LiOH (90%: 10%, wt%). This new study suggests an innovative, sustainable path for the capture and conversion of CO\({}_{2}\) driven by electrical energy or other renewable sources.