Electrodeposition was performed at a potential range of -1.0 to +0.2 V/SCE for 50 scans using an Autolab PGSTAT302N workstation. During the deposition process, the stirring rate was kept constant at 1000 rpm. After that, the catalyst was calcined under vacuum at 250 °C for 1 hour and then annealed in air at 350 °C for 4 hours. The loading mass is about 1.6 mg. The Co1.5Ga1.5O4, Co2.5Ga0.5O4, and Co1.5Al1.5O4 catalysts were synthesized following a process similar to that of the Co3O4 catalyst, with addition of Co(NO3)2•6H2O (0.05 M and 0.083 M), Ga(NO3)3•xH2O (0.05 M and 0.017 M), and Al(OH)(C2H3O2)2 (0.05 M) precursors. The geometric surface area of the samples was ~0.25cm 2 . In order to confirm the identity of these compounds, they were further characterized with XPS, XRD and SEM. SEM was performed using a Hitachi SU7000. XRD was performed using a Bruker D8; all materials were exposed to Cu-Kα radiation (λ=0.15406nm) and the data was collected with a point step of 0.02°. The XPS spectra in this study were analysed using the ThermoAvantage software. All XPS spectra were calibrated based on the position of the C1s peak in each spectrum and the Co2p peak convolution was performed using the same software as well. A Shirley background was used to determine the background of the XPS spectrum. Electrochemical characterization. Electrochemical data was collected using a three-electrode system connected to an electrochemical workstation (Autolab PGSTAT302N) SCE and a carbon rod were used as reference and counter electrodes, respectively. 1 M KOH without saturated O2 was used as the electrolyte. Cyclic voltammetry (CV) measurements at 50 mV/s were performed for 3 cycles prior to recording linear scan voltammetry (LSV) at 5 mV/s for each sample.