Membrane-free and low-voltage oxygen generator using metal hydride mediated water splitting

While electrolytic water oxygen generation equipment is widely used in industrial and medical sectors, its broader adoption is hindered by high-voltage input requirement and reliance on costly proton exchange membranes , leading to high operational costs, maintenance demands and reliability issues. Herein, we developed a membrane-free, low-voltage oxygen generator utilizing a samarium-based metal hydride (Sm0-MH) cathode. This cathode features a low plateau pressure, low Tafel slope and a higher diffusion coefficient , and thus operates at an exceptionally low voltage of −17.5 mV vs. RHE. The Sm0-MH cathode, not only drives the water-splitting reaction by breaking hydrogen bonds but also efficiently absorbs the resulting hydrogen, which effectively elevates oxygen concentration from 20.9 % to 29.5 %. Meanwhile, we propose a shrinking-core model that extends traditional empirical theories typically applicable only at equilibrium states. To help select the alloy that is more suitable for devices through the basic parameters of some hydrogen storage alloys. Our model accounts for the dynamic behavior of MH shell on spherical particles by progressively reducing the volume of the hydrogen-storage alloy core, which also incorporates non-equilibrium states by adjusting hydrogen evolution rates to match current density variations. Additionally, the innovative coupling of a thermally desorbed and fully charged MH anode connected to a nickel hydroxide electrode to supply electricity not only repurposes the stored hydrogen for energy supply but also simplifies the system by avoiding complex catalyst requirements for hydrogen evolution reactions . This low-voltage, membrane-free oxygen generator has the potential to lower costs, improve reliability, and expand accessibility, potentially offering enhanced oxygen availability for applications in remote healthcare, high-altitude settings, or industrial uses. • The portable oxygen generator operates using metal hydrides as cathode at voltages (-17.5 mV vs. RHE) lower than 0 V vs. RHE. • The generator eliminates the need for PEMs and reduces the risk of dangerous hydrogen-oxygen mixing. • The Sm0-MH cathode efficiently absorbs the resulting hydrogen, elevating the oxygen concentration. • We propose a shrinking-core model that provides quantitative insights into the kinetic behavior of electrodes.