## 3 Results and Discussion
### Discharge Performance  
Based on the aforementioned different carbon electrodes, magnesium dissolution oxygen seawater cells were assembled with an AZ31 magnesium alloy as the anode. These cells were subjected to a constant current discharge of 50 mA for one hour to obtain the average discharge voltage for each carbon electrode (with at least three discharge experiments conducted for each carbon electrode). As shown in Figure 5, for the same carbon electrode with different binder ratios, the average discharge voltage for one hour initially decreases and then increases as the binder ratio increases within the range of 20-50%. The minimum value is observed at a binder ratio of 20%, while the maximum is reached at a binder ratio of 50%. The reason for this phenomenon is that the binder PTFE affects the porous structure and wettability of the carbon electrode, which in turn affects the oxygen diffusion process on the electrode. Increasing the binder ratio from 10% to 20%, the wettability of the carbon electrode decreases, the number of electrochemical reaction sites decreases, and the discharge reaction is limited to a certain extent, which leads to a decrease in the average discharge voltage at a binder ratio of 20%. However, the binder ratio was further increased to 50%, and the lower wettability increased the diffusion of oxygen in the non-wetted pores, which in turn enhanced the overall diffusion of oxygen within the porous structure. At the same time, the addition of PTFE increases the percentage of pores with larger pore sizes in the carbon electrode, increasing the utilization of larger-sized pores in the carbon electrode, and the high utilization of mesoporous and above pores is also conducive to the enhancement of oxygen diffusion. Therefore, the average discharge voltage increases when the binder ratio increases from 20% to 50%. In Figure 5, it is observed that the voltage generally increases and then decreases in discharge curves. This is because the anode magnesium alloy samples have an oxide film attached to the outside, which is first consumed to activate the electrode when the discharge reaction takes place. It is a common phenomenon during the repetition of experiments. Figure 5 also indicates  
Figure 4: Pore size distribution of different carbon electrodes. that for carbon electrodes with the same binder ratio, the Ketjen Black carbon electrode exhibits the highest average discharge voltage for one hour, followed by the Acetylene Black carbon electrode. The Vulcan XC-72R carbon electrode shows the lowest value. For example, at a binder ratio of 30%, the average voltage for one hour is 1.08 V for Acetylene Black-30% carbon electrode, 1.02 V for Vulcan XC-72R-30% carbon electrode, and 1.13 V for Ketjen Black-30% carbon electrode. As shown in Figure 2, the Ketjen Black carbon electrode has the largest specific surface area, and the number of its reaction sites is higher than the other two electrodes at low binder ratios. In Figure 4, the Ketjen Black carbon electrode has a higher macroporous capacity than both other electrodes. This indicates it has a better oxygen transport capacity at higher binder ratios, resulting in a higher discharge capacity. As a result, the Ketjen Black carbon electrode has the highest average discharge voltage among the three carbon electrodes, especially when the binder percentage is greater than 30%. For the Ketjen Black carbon electrode, when the proportion of binder is greater than 30%, the proportion of \"large holes\" in the carbon electrode is significantly more than the rest of the carbon electrodes, so the average discharge voltage is significantly better than the rest of the carbon electrodes. All carbon electrodes underwent single deep discharge specific capacity testing at a current intensity of 50 mA. Due to the low specific surface area, the discharge capacity  
Figure 5: One-hour average discharge voltage of different carbon electrodes.