A composite comprising a porous carbon structure comprising a surface and pores and a coating on the surface comprising MnO2, wherein the coating does not completely fill or obstruct a majority of the pores, and wherein the coating is formed by self-limiting electroless deposition. A capacitor comprising an anode, a cathode, and an electrolyte, wherein the anode, the cathode, or both comprise a composite comprising a porous carbon structure comprising a surface and pores and a coating on the surface comprising MnO2, and a current collector in electrical contact with the composite.