Hierarchical NiFe2O4-NiAl-LDH arrays immobilized on activated carbon cloth for bifunctional application on high-performance supercapacitors and solar steam generation

Spinel ferrite, with the characteristics of multiple oxidation states, good electrochemical stability, and excellent light absorption properties, shows great potential as an energy storage electrode and photothermal conversion material. Thereby, bifunctional material based on NiFe2O4 spinel ferrite in supercapacitor and solar steam generation is proposed for the first time in this work. NiFe2O4-NiAl-LDH-ACC, the composite with hollow and layered nanosheet structures was prepared by hydrothermal growth of NiAl-layered double hydroxide (NiAl-LDH) on the surface of activated carbon cloth (ACC) as well as NiFe2O4. The uniform growth of NiAl-LDH on the surfaces of ACC and NiFe2O4 further improves the overall structural stability, and the synergy effect between different metal compounds enhances the electrochemical and conductivity performance of the composites. Furthermore, ACC, as a photothermal conversion material, shows benign light absorption and hydrophilicity, which further enables the composite material to obtain high solar vapor generation rate by combining with NiFe2O4. As a result, NiFe2O4-NiAl-LDH-ACC composite display an eminent specific capacitance (2015 F g-1 at 1 A g-1) and a favorable evaporation rate (1.73 kg m- 2 h-1 under 1 kW m-2). In addition, the asymmetric supercapacitor with NiFe2O4-NiAl-LDH-ACC as the positive electrode and activated carbon (AC) as the negative electrode present excellent energy density (72.2 Wh kg- 1 at 830.2 W kg -1) and outstanding cycling stability (85.5% retention after 10,000 cycles). In the era of energy scarcity when single functional materials cannot satisfy applications in multiple scenarios and development faces limitations, it is obvious that NiFe2O4-NiAl-LDH-ACC, as a bifunctional material, provides vital design inspiration and enlightenment for both energy storage and photothermal conversion.