Manganese metal can serve as a secondary energy carrier for hydrogen, offering a cost-effective solution for energy storage and transport. This process can be realised through the hybrid manganese cycle. In this study, a large-sized electrolyser was specifically designed to perform the complete circulation of water splitting. The results indicate that the designed electrolyser significantly reduces the mass transfer impedance. However, the zero-gap structure on the anode side proves unsuitable for this system, as it leads to the occurrence of the manganese oxidation reaction (MOR), even when potassium sulphate is employed as a reaction inhibitor. In addition to its role in inhibiting manganese oxidation, the anodic addition of potassium sulphate was revealed to reduce the onset cell voltage of the manganese electrodeposition reaction (MEDR) and the current density. The optimal concentration of potassium sulphate in the anolyte was determined to be 0.2 mol/L. Furthermore, an anode-PEM distance of 2.5 mm was found to be most appropriate, as it ensures a sufficient local proton environment to completely inhibit manganese oxidation while also improving the current density. In addition, electrolyte circulation was optimised, with the best performance observed at a peristaltic pump speed of 100 rpm. Based on the optimised electrolyser, production tests were conducted. It was found that electrolysis duration influences both the manganese and hydrogen current efficiencies, thus affecting the overall energy conversion efficiency (OECE). The most favourable electrolysis was achieved at a duration of 600 s, resulting in improvements in the OECE, current density, and productivity by 3.47 %, 179.84 %, and 115.22 %, respectively, compared to the H-cell.