A significant overpotential necessary for the electrochemical oxygen evolution reaction (OER) is one of the most serious disadvantages in water electrolysis, which, on the contrary, gives the probability to electrochemically produce ozone alternative to the common corona discharge. To effectively suppress the competitive OER and improve gaseous ozone escaping, here we present a capillary effect-enabled electrolysis strategy by employing an unusual partial-submersed mode of anode composed of a beta-PbO2 cuboids-loaded bulk porous Pb, and realize a much enhanced electrocatalytic gaseous ozone production in comparison to the cases of solid Pb counterpart and/or usual submersion operation. Detailed study reveals a capillary pressure-induced "molecular oxygen-locking effect" in the electrolyte fully filled in the porous structure of the electrode area above the electrolyte pool level, which unexpectedly leads to the production of unusual center dot O-3(-) intermediate. Distinctive from the traditional electrochemical ozone production (EOP) mechanism dependent on the essential reaction between the atomic oxygen and molecular oxygen, the center dot O-3(-) intermediate generation favors the EOP process in the special case where the capillary action is relevant for a porous bulk anode.