Well-defined cobalt oxalate (CoC sub(2)O sub(4).2H sub(2)O) microstructures with controllable morphologies have been successfully synthesized by a simple solvothermal process. The resulting CoC sub(2)O sub(4).2H sub(2)O microrods (MRs) and micropolyhedrons (MPs) can be easily controlled by rationally tuning the composition of solvents. It is experimentally demonstrated that CoC sub(2)O sub(4).2H sub(2)O microstructures as nonprecious metal based electrocatalysts exhibit remarkable activity for catalyzing OER in alkaline medium. Such performance is found to be closely dependent on the morphology of CoC sub(2)O sub(4).2H sub(2)O microstructures. The MRs with higher aspect ratio and more active Co sites manifest a small OER onset potential, large anodic current and long-term durability, which are superior to the MPs, derived Co sub(3)O sub(4) MRs, and previously reported cobalt oxalate electrocatalysts, and even compare favorably with most previously reported Co-based OER electrocatalysts.