The successful implementation of direct anodic epoxidation relies on the compatibility of electrolyte system with specific catalysts and alkene substrates. In the oxidation of various alkene substrates using a water-acetonitrile mixed electrolyte, acetonitrile enhances the solubility of hydrophobic substrates, but organic solvents may increase the overall resistance of the electrolyte. When water is used as the sole solvent, gas-diffusion electrodes can address the low solubility issue of propylene. Therefore, water electrolyte is sufficient for epoxide production. PdPtO_x/C catalyst on a gas-diffusion electrode exhibited an average Faradaic efficiency of approximately 60% for propylene epoxidation at a potential of 1.65 V (vs. SHE).