Reduction of aqueous Cu(II) and Co(II) is one critical step for simultaneous recovery of copper and cobalt, and recycle of spent lithium ion batteries, but suffers from consumption of large amount of energy and chemicals. Here we report Co(II)-reduced microbial electrolysis cells (MECCo) can be driven by Cu(ll)reduced microbial fuel cells (MFCCu) for simultaneous Cu(II) and Co(II) recovery with no external energy consumption, and system performance was heavily dependent on cathode material of MECo, and cathode volumes in both MECCo, and MFCCu. Either titanium sheet (TS) or stainless steel mesh (SSM) cathode achieved efficient Co(II) reduction whereas carbon rod (CR) cannot proceed this occurrence. While smaller cathode volumes in MFCa, led to appreciable Co(II) reduction (41.4 3.8%) on the CR cathode, the highest Co(II) reduction using TS (45.0 0.3%) or SSM (39.7 3.6%) was obtained under smaller cathode volumes in both MFCCu and MECCo. Moreover, when a mixed Cu(II) and Co(II) catholyte was deliberately used as the influent of MFCCu and the effluent of MKo was subsequently imported into the connected MECo, for tentatively simultaneous Cu(II) and Co(II) recovery from simulated mixed wastes, this so-called sequential MFCCu and MFCCu operation achieved Cu(II) reduction of 100% and Co(II) reduction of 65.3-72.0% using either TS or SSM cathodes. These results illustrate cathode material of MECo, and cathode volumes in both MECCo, and MFCCu, were critical for efficient Co(II) reduction in MEC, driven by MFCa, with achievements of simultaneous copper and cobalt recovery as well as no external energy consumption. 2014 Elsevier B.V. All rights reserved.