Electrochemical cells and batteries that can operate with a single electrolyte solution, such as those comprising an anode, a cathode current collector, and a porous, non-conductive spacer between the cathode current collector and anode. Membraneless electrochemical cells and batteries are also disclosed. The electrochemical cells and batteries disclosed herein may be used, for example, to produce electricity or to generate hydrogen or both, and to deliver electricity or hydrogen or both to process applications.