The sustainability of conventional water-and energy-associated systems is being examined in terms of water-energy nexus. This study presents a high-efficiency, off-grid solar desalination system for saline water (salinity 10 and g L −1) that accompanies electrocatalytic oxidations of chloride and, consequently, urine via oxidized chlorine species, while concomitantly producing formate from captured CO2. A variable number of desalination cell arrays is placed between a double-layered nanoparticulate titania electrocatalyst (Ti/IrxTa1−xOy/nano-TiO2; denoted as n-TEC) anode and a porous dendrite Bi cathode. A potential bias to the n-TEC and Bi pair initiates the transport of chloride and sodium ions in the saline water to the anode and cathode cells, respectively, at an ion transport efficiency of ~100% and a specific energy consumption of ~1.9 kWh m −3. During the desalination, the n-TEC anode catalyzes the conversion of the transported chloride into reactive chlorine species, which in turn mediate the decomposition of urine in the anode cell. Concurrent with the anodic process, formate is continuously produced at a Faradaic efficiency of >95% from the CO2 captured in the catholyte. When a photovoltaic cell (power conversion efficiency of ~18%) is coupled to the stack device with five desalination cells, the three independent processes synergistically proceed at a maximum overall solar-to-desalination system efficiency ~16% and a maximum solar-toformate chemical energy conversion efficiency of ~7%.

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