The trick behind the material lies in how it is made. Rather than precipitating nickel sulfide particles directly from solution, the researchers used a metal-organic framework, or MOF, as a sacrificial template. MOFs are crystalline lattices built from metal ions connected by organic linker molecules, and they are famous for being riddled with regularly spaced pores at the molecular scale. By converting this framework through a sulfurization strategy, the team preserved a memory of the original porous structure while transforming the chemistry from a hybrid organic-inorganic framework into a pure inorganic sulfide. The result is a sponge-like NiS2 architecture in which mesopores, pores in the range of roughly two to fifty nanometers, are abundant and interconnected, producing a high specific surface area that would be difficult to achieve by conventional synthesis routes.

That architecture matters because the performance of a battery or supercapacitor electrode is governed largely by how easily ions can reach the electroactive sites where charge storage happens. In a dense, poorly connected material, ions from the electrolyte must diffuse long distances through tortuous pathways, and much of the interior of the material is effectively wasted. In the sponge-like NiS2, the abundant mesopores act as highways for hydroxide ions and other electrolyte species, shortening diffusion lengths dramatically, while the large surface area exposes a vast number of electroactive sites for the surface redox reactions that store charge. The hierarchical porosity also helps accommodate the volume changes that accompany repeated charging and discharging, a key factor in the material’s observed cycling stability.

The electrochemical results are the heart of the study. When tested as a supercapacitor electrode in alkaline electrolyte, the NiS2 electrode delivered a specific capacitance of 1227.5 F g−1 at 0.5 A g−1, a value that reflects an exceptional density of accessible charge-storage sites. Specific capacitance measures how much electric charge a gram of electrode material can hold per volt of potential, and values above one thousand farads per gram are characteristic of high-performance pseudocapacitive materials, which store charge through fast, reversible surface reactions rather than purely electrostatic adsorption. Nickel sulfides are well suited to this role because nickel can shuttle between multiple oxidation states during charging and discharging, enabling rich redox chemistry at the electrode surface.

Perhaps the most commercially interesting finding is that the material is bifunctional. The same NiS2 electrode that excels in a supercapacitor configuration can also serve as the cathode in an aqueous nickel-zinc battery, where it delivers high specific capacity and stable long-term performance. Ni-Zn batteries are an attractive technology because they use water-based electrolytes, which are inherently safer and cheaper than the flammable organic solvents found in lithium-ion cells, and because zinc is abundant and easy to handle. The catch has historically been finding cathode materials that can withstand the demanding alkaline environment while storing enough charge to make the cells competitive. The demonstration that a single MOF-derived sulfide can serve both device types suggests a versatile platform rather than a one-off material.

The study situates itself within a broader surge of interest in aqueous energy storage. Water-based devices occupy a compelling middle ground between supercapacitors, which charge in seconds but store limited energy, and conventional batteries, which store more energy but charge more slowly and carry greater safety burdens. Recent literature highlighted in the paper’s reference list spans electrochemical activation tactics for aqueous devices, rechargeable zinc-based storage, molecularly crowding electrolytes for micro-supercapacitors, and flexible yarn-like Ni-Zn batteries for wearable electronics. Transition metal sulfides, including nickel sulfides such as Ni3S4 and NiS2, have emerged as leading candidates in this space because they combine high theoretical capacity, good electrical conductivity relative to oxides, and low cost.

The MOF-derived approach itself is part of a wider design philosophy in materials chemistry. By using a preassembled framework as a template, chemists can impose order on a material at the nanoscale that would be hard to achieve through direct synthesis. In this case, the sulfurization step converts the nickel-containing framework into NiS2 while retaining the sponge-like morphology, a process analogous to casting a sculpture in a mold. Earlier work by some of the same authors produced accordion-like iron-doped NiS2 and surface-amorphized nickel sulfides for aqueous storage, indicating that the group has been systematically exploring how morphology and surface chemistry tune the performance of nickel sulfide electrodes. The new sponge-like architecture extends that program by emphasizing interconnected mesoporosity as the central design feature.

There are, of course, caveats that temper any immediate industrial enthusiasm. The reported measurements were made on laboratory-scale electrodes in alkaline electrolyte, and translating a promising lab material into a commercial device requires solving problems that go beyond the cathode itself, including zinc anode durability, electrolyte optimization, and full-cell engineering. The paper’s own framing is careful: the authors describe the work as establishing NiS2 as a promising electrode material for aqueous energy storage devices and providing a feasible synthetic pathway for designing high-performance transition metal sulfide electrodes, rather than claiming a ready-made product. Still, the combination of high capacitance, cycling stability, and bifunctionality in a single low-cost material is exactly the kind of result that device engineers look for when deciding which candidates to pursue.

The broader significance of the work lies in its demonstration that structure, not just composition, is the lever that unlocks performance. Nickel disulfide has been recognized as a sustainable, low-cost electrode material before, but the sponge-like hierarchical architecture reported here shows how much headroom remains in a familiar compound when its porosity is engineered deliberately. As the demand for safe, inexpensive, grid-scale and wearable energy storage continues to grow, strategies that turn molecularly precise templates into functional inorganic electrodes are likely to play an increasing role. For now, a synthetic sponge made of nickel and sulfur, born from a crystalline framework and hardened into a charge-hungry electrode, offers a vivid example of how rational design at the nanoscale can translate directly into better electrochemical numbers.

Subject of Research: MOF-derived hierarchical porous NiS2 electrode materials for aqueous supercapacitors and Ni-Zn batteries

Article Title: MOF-derived sponge-like NiS2 with a hierarchical porous architecture for aqueous supercapacitors and Ni-Zn batteries

Article References: Gong, G., Liu, X., Ma, H., Lv, D., Luo, H., Liang, M., Zhou, Y., Wang, H., Zhao, Y., Lashari, N. U. R., & Miao, Z. (2026). MOF-derived sponge-like NiS2 with a hierarchical porous architecture for aqueous supercapacitors and Ni-Zn batteries. Ionics. https://doi.org/10.1007/s11581-026-07558-0

Image Credits: AI Generated

DOI: 10.1007/s11581-026-07558-0

Keywords: NiS2, metal-organic framework, supercapacitor, Ni-Zn battery, aqueous energy storage, transition metal sulfide, mesoporous structure, electrode material, pseudocapacitance, sulfurization, energy storage, Ionics