## 4 Conclusions  
We prepared three kinds of porous carbon electrodes with different PTFE ratios for magnesium-dissolved oxygen seawater cells. Structural characterization of all carbon electrodes was conducted using nitrogen adsorption-desorption experiments. Based on the prepared carbon electrodes, magnesium-dissolved oxygen seawater cells were assembled and subjected to constant current discharge testing, leading to the following conclusions:  
(1) When the PTFE ratio in the carbon electrode is within the range of 10-50%, the number of micropores and pores with diameters in the range of 2-10 nm decreases continuously, while the average pore size of the carbon electrode increases. The specific surface area of the carbon electrode is mainly affected by micropores and small-sized pores, which decreases as the PTFE ratio increases.  
As the binder ratio increases, the average pore size of the carbon electrode increases continuously.  
(2) When the PTFE ratio is within the range of 10-50%, the performance of the magnesium-dissolved oxygen seawater cell initially decreases and then increases. In the working environment where oxygen is hard to acquire, when the PTFE ratio in the carbon electrode is less than 20%, it is speculated the performance of the seawater cell is mainly influenced by the number of reaction sites. An increase in the PTFE ratio leads to a decrease in the performance of the seawater cell. When the PTFE ratio in the carbon electrode is greater than 20%, the performance of the seawater cell is primarily influenced by oxygen diffusion on the carbon electrode. An increase in the PTFE ratio enhances the performance of the seawater cell.  
(3) Among the different carbon electrodes with the same PTFE ratio, the Ketjen Black carbon electrode exhibits the best performance. The single deep discharge specific capacity of the Ketjen Black carbon electrode with a 50% PTFE ratio can reach 11.86 Ah/g, followed by the Acetylene Black carbon electrode, and the VulcanXC-72R carbon electrode performs the worst. The electrode with a binder ratio over 50% is not recommended since it can significantly reduce the electrical conductivity.  
The following supporting information can be downloaded at: [[https://www.mdpi.com/article/10.3390/app132412996/s1](https://www.mdpi.com/article/10.3390/app132412996/s1)]([https://www.mdpi.com/article/10.3390/app132412996/s1](https://www.mdpi.com/article/10.3390/app132412996/s1)). Figure S1: N\({}_{2}\) adsorption-desorption isotherms of different carbon electrodes.  
Conceptualization, F.W.; methodology, X.H.; formal analysis, W.L.; investigation, Y.C.; resources, F.W.; data curation, X.H.; writing--original draft preparation, Y.C.; writing--review and editing, W.L.; funding acquisition, F.W. and J.T. All authors have read and agreed to the published version of the manuscript.  
This research was funded by the National Natural Science Foundation of China (Grant No. 52006046) and the Key R&D Program of Shandong Province, China (2022 ZLGX04).  
Not applicable.  
The data can be available for research purposes only. All those interested can contact the author directly via email. The data are not publicly available due to privacy.  
The authors declare no conflict of interest.