In this work, powdered hierarchical CuxCo3−xO4 catalysts were used as catalysts for the oxygen evolution reaction (OER) in an alkaline anion exchange membrane water electrolyzer (AAEMWE). The effect of increasing Cu concentration (x = 0, 0.25, 0.5, 0.75, and 1) on the OER catalysis performance of the spinel Co3O4 was studied. In general, Cu-doped Co3O4 samples performed better than the undoped spinel catalyst. The sample synthesized with Cu-doping at x = 0.75 (CCO-0.75) performed the best among the catalysts tested with an overpotential of 385 mV at 10 mA cm−2 in 1 M KOH, which is 24% lower than that recorded for the undoped Co3O4 sample. An AAEMWE was assembled using CCO-0.75 on Ti gas diffusion layer (GDL), and Pt/C on carbon GDL as the anode, and cathode, respectively. The CCO-0.75||Pt/C cell required only 1.65 V to reach 100 mA cm−2 at 60 ℃ in 1 M KOH.