Copper tungstate deposited reduced graphene oxide nanocomposite for highly efficient capacitive deionization

[Display omitted] •Copper tungstate decorated reduced graphene oxide (CWO/rGO) was solvothermally synthesized.•A high specific capacitance of 380F g−1 for CWO/rGO is obtained.•An excellent SEC of 54.1 mg g−1 is achieved in the presence of 1000 mg L-1 NaCl at 1.4 V.•CuWO4 provides electroactive sites for Faradaic capacitance.•rGO enhances the electric conductivity and provides mesoporous channels for enhanced CDI. Copper tungstate (CuWO4) decorated 2-dimensional reduced graphene oxide (CWO/rGO) has been successfully fabricated via solvothermal synthesis at 180 °C for 12 h, and then utilized for capacitive deionization (CDI) applications. After deposition of 20 – 40 nm spherical CuWO4 nanoparticles onto few-layered rGO nanosheets, the specific surface area can be up to 338 m2 g−1 with abundant 2 – 10 nm mesopores, which can accelerate the ion transport to augment the electrochemical performance. The CWO/rGO nanocomposite also exhibits high specific capacitances of 380 and 327 F g−1 at 0.5 A g−1 and 5 mV s−1, respectively. Furthermore, the specific electrosorption capacity (SEC) of CWO/rGO is highly dependent on environmental parameters including NaCl concentration, flow rate, applied potential, and solution temperature. An excellent SEC of 54.1 mg g−1 is achieved when 1000 mg L-1 NaCl was used at 1.4 V. Both Faradaic and electric double layer capacitances contribute the electrosorption capacity to the CDI performance of CWO/rGO where CuWO4 provides electroactive sites and rGO enhances the electric conductivity as well as offers mesoporous channels for electrosorption of ions. Meanwhile, the high charge efficiency of 95 %, lower energy consumption of 0.32 kWh m−3, and long-term stability of 50 charging-discharging cycles make the CWO/rGO a potential material for brackish water desalination, which can elucidate on the development of highly efficient desalination technologies.