This paper examines an experimental oxygen production reactor designed and built at UOIT to simulate processes encountered in electro-catalytic water splitting systems for hydrogen production. In a complete system, a major portion of the over-potential is due to electrochemical processes at the anode, where oxygen evolution occurs. In this paper, the effects of ohmic, concentration and activation losses on the efficiency of hydrogen production by water electrolysis are experimentally investigated. The water electrolysis of a potassium hydroxide aqueous solution is conducted under atmospheric pressure using Ni and graphite electrodes. The electrochemical performance of the system is examined by controlling the current density, temperature, space, height, and electrolyte concentration. A commercial anion exchange membrane is employed to investigate the charge and ion transfer between two reactors. The performance of water electrolysis is qualitatively evaluated by the voltage drop measurements and hydrogen production rate at specified current densities. The experimental results show that there exists an optimum working condition of water electro-catalysis at each current density, which is determined by the controlling parameters. A predictive mathematical model based on experimental data is developed and the optimized working conditions are determined. In addition, a transient model of mass and ion transport between the electrodes is presented.