## 3 Results and Discussions
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multirow{2}{*}{**Materials**} & \multicolumn{2}{c}{**Cycle 1**} & \multicolumn{2}{c}{**Cycle 2**} & \multicolumn{2}{c}{**Cycle 3**} \\ \cline{2-7}  & \(\mathbf{n_{O}}\)**, **Released** & \(\mathbf{n_{CO}}\)** **Produced** & \(\mathbf{n_{O}}\)**, **Released** & \(\mathbf{n_{CO}}\)** **Produced** & \(\mathbf{n_{O}}\)**, **Released** & \(\mathbf{n_{CO}}\)**Produced** \\  & **(\(\upmu\)mol/g)** & **(\(\upmu\)mol/g)** & **(\(\upmu\)mol/g)** & **(\(\upmu\)mol/g)** & **(\(\upmu\)mol/g)** \\ \hline CeO2 & 47.1 & 94.2 & 47.8 & 95.6 & 46.9 & 93.8 \\ \hline ACRM & 199.8 & 123.2 & 51.2 & 102.4 & 50.9 & 101.8 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Amounts of O2 released and CO produced by ACRM and pure CeO2 during three consecutive thermochemical CDS cycles. Figure 8: TGA profiles obtained during three consecutive ACRM-driven thermochemical CDS cycles. This study aimed to investigate the stability of ACRM in terms of its phase composition and microstructure, in addition to the redox reactivity. The post-reaction ACRM obtained after ten consecutive thermochemical CDS cycles was characterized using PXRD and SEM. The PXRD patterns of the pre- and post-reaction ACRM are depicted in Figure 11. As per the PXRD analysis, the phase composition of the ACRM remained unchanged even after undergoing ten thermochemical CDS cycles. Figure 10: Amounts of O2 released and CO produced by ACRM during ten consecutive thermochemical CDS cycles. Figure 9: TGA profiles obtained during ten consecutive ACRM-driven thermochemical CDS cycles. SEM analysis examined the ACRM samples obtained after 1 and 10 thermochemical cycles. Sintering of ACRM after the first cycle was observed in the SEM image presented in Figure 12a, indicating a significant increase in particle size from nanometers to microns. However, the SEM image in Figure 12b showed no further increase in particle size after performing 10 thermochemical cycles. This finding confirms that sintering of ACRM occurs upon exposure to high operating temperatures during the first cycle. No further sintering is observed once the material is stabilized after the initial thermochemical cycle. This is consistent with the levels of O\({}_{2}\) released and CO produced by ACRM, as higher levels were recorded during the first cycle, while significantly lower amounts were observed during the second cycle, which could be attributed to ACRM sintering. Conversely, from the second to the tenth cycle, the redox reactivity of ACRM remained consistent, as no further sintering was observed. Figure 11: PXRD patterns of ACMR before and after performing 10 consecutive thermochemical CDS cycles. Figure 12: SEM images of ACRM after performing (**a**) 1 cycle and (**b**) 10 cycles. The investigation conducted on the redox reactivity of CeO\({}_{2}\) with Ag doping has shown promising results. Our research indicates that the amounts of O\({}_{2}\) released and CO produced by ACRM are not extremely high compared with those produced by pure CeO\({}_{2}\). However, it is important to note that we have only tested one composition of ACRM (1% Ag-doped in CeO\({}_{2}\): Ce\({}_{0.99}\)Ag\({}_{0.01}\)O\({}_{2-8}\)). Besides, the findings of this study provide a pathway to improve the redox reactivity of CeO\({}_{2}\) by incorporating Ag in its crystal structure. Our future plans entail investigating the impact of varying doping levels of Ag in the ceria crystal structure (ranging from 1 to 10%) on the thermochemical conversion of H\({}_{2}\)O and CO\({}_{2}\) into solar fuels. Additionally, we will conduct advanced material characterizations, such as TEM mapping and XPS analysis [32], to analyze the elemental distribution and electronic structural characteristics of the Ce, Ag, and O elements.