## 3 Results and Discussion
### The Effects of LiOH Addition on the Cathodic Products  
It has been reported that the water electrolysis process powered by renewable energy such as solar and wind energy is a simple process of high purity, with green environmental protection, which is a sustainable method of hydrogen production [35]. In order to further transform CO\({}_{2}\) into high-value products, we investigated the effect of water addition on the cathodic products, including gaseous and solid products. The investigation on the effect of water addition was conducted on the basis of our previous works [22; 23; 24; 28]. Due to the serious operating difficulty in the input of water or vapor, LiOH is a viable alternative for replacing moisture to supply the hydrogen source. The electrolysis temperature here was 550 \({}^{\circ}\)C, which avoids the thermal decomposition of molten salt at high temperatures and the low conductivity caused by too-low temperatures. The electrochemical behavior was studied by cyclic voltammetry to analyze the differences between the pure carbonates and eutectic salts of the carbonates and hydroxides, and the result is shown in Figure 5.  
Figure 4: (**Left**) XRD of carbon nanotubes. (**Right**) Raman spectra of carbon nanotubes. Figure 5: Cyclic voltammetry recorded from an Ni anode and Fe cathode in Li\({}_{1.43}\)Na\({}_{0.26}\)K\({}_{0.21}\)CO\({}_{3}\) + 0.15 LiOH at 550 \({}^{\circ}\)C with different scanning rates. Figure 5 presents the cyclic voltammetry of the molten Li\({}_{2}\)CO\({}_{3}\)-Na\({}_{2}\)CO\({}_{3}\)-K\({}_{2}\)CO\({}_{3}\) + 0.15 LiOH at 550 \({}^{\circ}\)C with an Ni anode and Fe cathode at different scanning rates. The scanning result, compared with the preceding CV curve of pure carbonates, is distinguished by a slight reduction current peak, R1, between 0 V and 1 V, suggesting the reduction of H\({}^{+}\) to H\({}_{2}\). The next large reduction peak, R2, near 1.5 V, can be attributed to the generation of hydrocarbons (the vast majority are methane and a small number are ethane, propane, and other hydrocarbons). According to the previous theoretical calculation, the peak R3 at 2.5 V suggests the generation of CO, and R4 at 2.9 V suggests deposition of the metals K and Na (near 2.7 V, from the theoretical calculation). However, the Li deposition at 550 \({}^{\circ}\)C requires a much more significant negative potential and does not appear on the CV. In order to improve the efficiency of electrolysis, the investigation was carried out in a two-electrode cell under an Ar atmosphere, which can protect the electroactivity of two electrodes and expel the gaseous products to the sampling bag through a topside gas-guide tube. Li\({}_{1.427}\)Na\({}_{0.359}\)K\({}_{0.214}\)CO\({}_{3}\) and LiOH at the molar ratio of 0.15:1 were mixed and then co-electrolyzed at 550 \({}^{\circ}\)C under 2.0 V and 2.5 V for 30 min, and the gaseous products were sampled to test the gas composition by GC. Below we can see a figure of the gaseous products analysis results, showing that H\({}_{2}\), CH\({}_{4}\), and CO can be simultaneously detected in a TCD detector after adding LiOH. Furthermore, what catches our attention is the different percentages of CH\({}_{4}\) and CO under 1.5 V and 2.5 V. As can be seen in Figure 6, more CH\({}_{4}\) was obtained under 1.5 V. However, an unexpected decrease in CH\({}_{4}\) and an increase in CO were observed under higher voltages. A higher electrolysis voltage enables the generation of syngas (including H\({}_{2}\) and CO), while a lower electrolysis voltage is a proper condition to transform CO\({}_{2}\)/H\({}_{2}\)O into hydrocarbons (mainly composed of methane). In addition, a small amount of CO was also confirmed by gas chromatography equipped with a TCD detector, as shown in Figure 5. The TCD signal shows well-defined, isolated peaks of H\({}_{2}\), O\({}_{2}\), CH\({}_{4}\), and CO. The core of the co-electrolysis of CO\({}_{2}\)/H\({}_{2}\)O to produce hydrocarbon-rich fuel gas is the high temperature electrochemical reaction in the molten salt medium.