Binary Ni–Cu metal–organic framework@carbon nanotube hybrid for high-performance supercapacitors and efficient water splitting

Abstract

A binary nickel–copper metal–organic framework integrated with carbon nanotubes (NiCu-MOF@CNT) was successfully synthesized as a multifunctional electrode material for high-performance supercapacitors and efficient water splitting. The structural, morphological, compositional, and textural properties of the hybrid were systematically characterized by X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FT-IR), Thermogravimetric analysis (TGA & Dr-TGA), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and Brunauer–Emmett–Teller (BET) surface area analysis. The incorporation of CNTs effectively enhanced the electrical conductivity, surface area, and accessibility of electroactive sites. The NiCu-MOF@CNT electrode exhibited high supercapacitor performance, delivering a high specific capacitance of 1244 F g−1 at 1 A g−1, high rate capability with 69.1% capacitance retention at 1 to 6 A g−1, and remarkable cycling stability of 81.4% after 10 000 cycles. In addition, the hybrid demonstrated bifunctional electrocatalytic activity toward water splitting in alkaline electrolyte, achieving low overpotentials of 243 mV for the HER and 280 mV for the OER at 10 mA cm−2 (vs. RHE). Tafel slope analysis revealed favorable reaction kinetics with values of 110 mV dec−1 for the HER and 118 mV dec−1 for the OER, confirming accelerated charge–transfer processes and efficient catalytic pathways. The NiCu-MOF@CNT electrode also maintained high durability during continuous HER/OER operation for 20 h. Additionally, the overall cell voltage of the two-electrode electrolyzer was determined using a DC power supply. The NiCu-MOF@CNT/NF‖NiCu-MOF@CNT/NF system required a cell voltage of 2.1 V to deliver a current of 10 mA, demonstrating its effective catalytic activity toward overall alkaline water splitting.