Lignite-derived 3D Ni-MOFs: preparation and electrochemical performance as supercapacitor electrodes

Developing low-cost, high-performance electrode materials for supercapacitors remains a key challenge. Herein, 3D Ni-MOFs were prepared via a two-step method using lignite as the precursor: lignite was first oxidatively depolymerized to generate multi-component mixed organic ligands with abundant hydroxyl and carboxyl groups, which then coordinated with Ni²⁺ via hydrothermal assembly to form stable Ni–O bonds and hierarchical porous frameworks. The porous structure of the Ni-MOFs ensures rapid ion diffusion, while the Ni–O coordination sites enable highly reversible redox reactions, synergistically boosting the pseudocapacitive performance. The as-prepared Ni-MOFs showed superior pseudocapacitor performance, with a specific capacitance of 568.4 F·g⁻¹ at 5 mV·s⁻¹ and a discharge time of 1676.9 s at 1 A·g⁻¹, outperforming raw lignite and lignite-derived ligands. This work provides a feasible way for high-value utilization of lignite and the development of low-cost pseudocapacitor materials.Developing low-cost, high-performance electrode materials for supercapacitors remains a key challenge. Herein, 3D Ni-MOFs were prepared via a two-step method using lignite as the precursor: lignite was first oxidatively depolymerized to generate multi-component mixed organic ligands with abundant hydroxyl and carboxyl groups, which then coordinated with Ni²⁺ via hydrothermal assembly to form stable Ni–O bonds and hierarchical porous frameworks. The porous structure of the Ni-MOFs ensures rapid ion diffusion, while the Ni–O coordination sites enable highly reversible redox reactions, synergistically boosting the pseudocapacitive performance. The as-prepared Ni-MOFs showed superior pseudocapacitor performance, with a specific capacitance of 568.4 F·g⁻¹ at 5 mV·s⁻¹ and a discharge time of 1676.9 s at 1 A·g⁻¹, outperforming raw lignite and lignite-derived ligands. This work provides a feasible way for high-value utilization of lignite and the development of low-cost pseudocapacitor materials.