## 1 Introduction
When the pore size further increased to 100 nm, the discharge capacity gradually decreased. [PERSON] [25] changed the porous structure of the cathode by altering the formula of the air cathode in lithium-air batteries. Through testing, it was concluded that the discharge capacity increased linearly with the average pore size, while it had no significant relationship with the cathode-specific surface area. Additionally, [PERSON] et al. [26] studied porous cathodes in lithium-air batteries and found that the BET-specific surface area of the cathode does not strongly affect the discharge capacity of the battery. The reason is that the BET-specific surface area mainly depends on the number of micropores with diameters smaller than 2 nm. During the discharge process, the discharge products are prone to block the micropores, preventing oxygen from entering the micropores for the reaction. Therefore, the influence of micropores on oxygen transport in the cathode is negligible. [PERSON] [30] demonstrated that the discharge capacity of the cathode carbon material is related to the mesopore volume. Furthermore, there has been research on the wettability of cathodes. For example, [PERSON] and [PERSON] [34] studied the impact of electrode wettability on the discharge capacity of lithium-air batteries and concluded that hydrophobic electrodes have a higher discharge capacity due to enhanced oxygen diffusion compared to hydrophilic electrodes. Additionally, electrodes with mixed wettability have a higher discharge capacity due to a balanced number of reaction sites and diffusion paths in the electrode. In addition to experiments, simulations have also played a significant role in the study of cathode porous structures. [PERSON] [38] developed a statistical model to study the microstructural evolution of porous electrodes and combined it with computational fluid dynamics models to simulate the discharge performance of the electrode. The results indicated that when the pore size is smaller than the critical pore size, i.e., when the pore is too small to accommodate reactants, pores smaller than the critical size do not have an impact on the discharge capacity of the battery. Currently, research on metal-air batteries has rarely focused on magnesium-dissolved oxygen seawater batteries. This study primarily investigates the influence of PTFE binder ratios on cathode porous structure and further the performance of magnesium-dissolvedoxygen seawater batteries. In this experiment, carbon electrodes were prepared from three different commercial carbon blacks (acetylene black, VulcanXC-72R, and Ketjen black). The porous structure of the cathode was adjusted by changing the mass ratio of PTFE to the three carbons. Nitrogen adsorption-desorption experiments were performed to characterize the structure of the different porous carbon cathodes. Based on the prepared cathode porous structures, a magnesium-dissolved oxygen seawater battery was designed and fabricated with AZ31 magnesium alloy as the anode material. Constant current discharge tests were conducted to explore the influence of the cathode porous structure on the performance of the magnesium-dissolved oxygen seawater battery.