Northwestern University researchers have developed a liquid that stores energy by transforming into a gel, offering a new approach to chemical energy storage. The material starts as a yellow liquid and, when exposed to light, electricity, chemical fuels, or X-rays, absorbs electrons and reorganizes itself into a black, conductive hydrogel.
Related: New camera does it all on the go
The process relies on molecular self-assembly. The yellow liquid contains small globular aggregates that, upon accepting electrons, stack and bind through π-π interactions and radical “pimer” formation. This restructuring transforms the loose molecular arrangement into long supramolecular polymer fibers, stabilizing the stored charge. Under oxygen-free conditions, the gel can retain energy for months, with the charged state directly tied to its assembled structure rather than merely holding electrons like ions in a battery electrode.
To release the energy, oxygen is introduced. The gel transfers its stored electrons to oxygen, producing reactive oxygen species capable of driving oxidation reactions. Unlike traditional batteries, the system doesn’t deliver electrical current but instead powers chemical processes, such as degrading organic pollutants, sterilizing surfaces, or enabling oxidation of organic substrates. The stored energy is released as chemical redox activity, not as electrical output.
Related: British Business Bank pledges £90m for VC investors
Researchers describe it as a model for dark photocatalysis, where the material can be charged by light or other sources, stored, and later used to catalyze reactions without continuous energy input. In conventional photocatalysis, light must be present during the reaction, but this system decouples the charging and reaction steps, allowing stored energy to be deployed in dark environments. The material resets after use—once oxygen exposes the gel, it reverts to its original yellow liquid state through supramolecular disassembly and can be recharged repeatedly.
The work, published in the journal Chem, marks the first reported material that stores energy by physically rebuilding its structure. It integrates energy capture, storage, structural transformation, and catalysis into a single soft platform, blurring the distinction between components like battery electrodes or semiconductor materials. The system’s cell-inspired design captures and releases chemical redox energy on demand, with the useful output being chemical work rather than electrical discharge.
Related: British Bank backs new UK venture fund
The team emphasizes that this isn’t a replacement for conventional batteries. Instead, it offers a new way to store and deploy chemical energy, particularly for applications where reactions need to occur in the absence of light or immediate energy input. Long-term storage requires oxygen exclusion, as exposure to air triggers the release of stored electrons, resetting the material to its liquid form and enabling reuse.
