Disclosed are methods of making porous zinc electrodes. Taken together, the steps are: forming a mixture of water, a soluble compound that increases the viscosity of the mixture, an insoluble porogen, and metallic zinc powder; placing the mixture in a mold to form a sponge; optionally drying the sponge; placing the sponge in a metal mesh positioned to allow air flow through substantially all the openings in the mesh; heating the sponge in an inert atmosphere at a peak temperature of 200 to 420° C. to fuse the zinc particles to each other to form a sintered sponge; and heating the sintered sponge in an oxygen-containing atmosphere at a peak temperature of 420 to 700° C. to form ZnO on the surfaces of the sintered sponge. The heating steps burn out the porogen.