A solution-assisted etching preparation of an MOF-derived NH4CoPO4·H2O/Ti3C2Tx MXene nanocomposite for high-performance hybrid supercapacitors

Abstract

Hydrated ammonium metal phosphates (AMPs) with numerous electractive sites and intercalated water are the current research focus in the field of supercapacitors. Herein, we have developed a novel approach where Co-MOF(ZIF-67) as a precursor was introduced into the confined space of an MXene layer, and the as-prepared MOF/Ti₃C₂T_x was subsequently etched in situ in a solution of (NH₄)₂HPO₄ to transform into NH₄CoPO₄·H₂O nanoparticles with a uniform distribution on the surface of Ti₃C₂T_x. NH₄CoPO₄ nanoparticles were embedded into MXene nanosheets, while the Ti₃C₂T_x MXene endowed AMPs with high electronic conductivity. Benefiting from the synergistic effect of NH₄CoPO₄·H₂O and MXene, this material showed good rate performance (601 F g⁻¹ at 1.0 A g⁻¹ and 535 F g⁻¹ at 20.0 A g⁻¹) and long cycle life (87% capacitance retention up to 5000 cycles at 5 A g⁻¹) in a three-electrode system, which can be ascribed to excellent electronic conductivity and short ion transport path. When NH₄CoPO₄·H₂O/Ti₃C₂T_x and activated carbon are used as the positive and negative electrodes of asymmetric supercapacitors (ASCs), the ASC simultaneously shows high energy density (47 W h kg⁻¹ at 1350 W kg⁻¹) and power density (18 W h kg⁻¹ at 5000 W kg⁻¹), which can be considered as a potential candidate for next-generation energy storage devices.