Integrated Photothermal Desalination–Thermo-Electrochemical System Enabled by Cobalt Oxide–Graphite Felt Electrodes

Solar-driven interfacial evaporation offers a promising solution to the global water scarcity crisis, yet its potential is constrained by insufficiently innovative designs for enhancing the utilization of low-grade heat. To address this issue, an integrated system of photothermal desalination–thermo-electrochemical conversion is proposed based on a cobalt oxide-modified graphite felt dual-functional electrode (CoO@GF). The performance of the electrode and the system is systematically investigated. Physicochemical characterizations confirm the coexistence of Co2+/Co3+ and the concentration-controlled morphologies on the electrode surface. Electrochemical tests show that the CoO@GF electrode exhibits significantly reduced charge-transfer resistance (17.4 Ω) and an improved electrochemically active surface area. Photothermal evaporation experiments demonstrate that the CoO@GF electrode exhibits enhanced solar absorption capacity, leading to improved water evaporation performance. Under 1 sun illumination, the optimized electrode reaches a water evaporation rate of 2.12 kg·m–2·h–1 and an evaporation efficiency of 89.5%. In the photothermal–thermo-electrochemical cell, the electrodes maintain a temperature difference of 13 °C. The open-circuit voltage and maximum power density are 19 mV and 1.20 mW·m–2, respectively, higher than those of the control electrode. The results demonstrate that the CoO@GF electrode shows remarkable photothermal and thermo-electrochemical conversion performance, providing a promising, controllable strategy for solar-driven desalination and low-grade heat energy harvesting.