The material at the heart of the study is a high-entropy oxide with the formula (FeCoMnCuZn)3O4, a spinel in which five different metal cations, iron, cobalt, manganese, copper, and zinc, share a single crystal lattice in roughly equimolar proportions. High-entropy materials have become one of the most exciting frontiers in materials chemistry precisely because of this compositional chaos. When four or five elements are forced to coexist in one phase, the resulting compound often exhibits properties that no single-component analogue can match: enhanced structural stability, tunable electronic states, and a wealth of synergistic interactions between neighboring cations. For supercapacitor electrodes, where charge is stored through fast, reversible Faradaic reactions at the surface, having five electroactive metals working in concert is a considerable advantage.

Writing in the journal Ionics, Zijing Tian, Fanen Zeng, Yuhan Liang, Zilong Zhou, and Bing Xu describe a coprecipitation route followed by calcination in air as their synthesis platform. The chemistry is conceptually simple: dissolve salts of the five metals, add a base to precipitate a mixed hydroxide or carbonate precursor, and then heat the precipitate to drive the formation of the mixed oxide spinel. But the devil, as so often in synthesis, lies in the details. The team systematically varied both the type of precipitant and, crucially, the dosage of sodium carbonate, the precipitant that ultimately proved decisive. The dosage determines how quickly and completely the metal ions are pulled out of solution, which in turn governs the nucleation and growth of the precursor particles and, after calcination, the phase purity, crystallinity, and morphology of the final oxide.

The experiments revealed a clear optimum. When 10 millimoles of sodium carbonate were used, the resulting powder was a single-phase spinel with relatively high crystallinity, uniform nanoparticle morphology, and a homogeneous distribution of all five metals across the particles. Samples prepared with other dosages deviated from this ideal, underscoring how sensitive high-entropy phase formation is to the kinetics of precipitation. In a five-component system, any compositional inhomogeneity introduced at the precipitation stage can seed secondary phases or elemental segregation during calcination, and both are detrimental to electrochemical performance. The 10 millimole condition effectively threaded the needle, producing the disordered yet single-phase structure that high-entropy design principles call for.

X-ray photoelectron spectroscopy added a deeper layer of insight into why the optimized material performs so well. The analysis confirmed the coexistence of multivalent species of iron, cobalt, manganese, and copper on the surface, alongside oxygen-vacancy-related defects. This redox-rich, defect-laden surface chemistry is exactly what an electrode for pseudocapacitive charge storage needs. Multivalent cations provide multiple accessible oxidation states for reversible Faradaic reactions, while oxygen vacancies act as charge carriers and active sites that facilitate electron transfer. In combination, they shorten diffusion paths for electrolyte ions and lower the kinetic barriers for charge transfer, allowing the electrode to store charge quickly without sacrificing capacity.

The electrochemical results speak for themselves. The 10 millimole electrode delivered a specific capacitance of 416.4 farads per gram at a current density of 1 ampere per gram, an excellent value for a five-metal oxide. More telling is what happened under stress: even when the current density was increased twentyfold to 20 amperes per gram, the electrode still delivered 207.4 farads per gram, retaining roughly half of its low-rate capacity. Rate capability of this quality indicates that ions and electrons can move in and out of the material fast enough to keep up with aggressive charging, a direct benefit of the uniform nanoparticle morphology and the conductive, defect-rich lattice engineered through the precipitation step.

A single electrode, however, does not make a device. To demonstrate practical relevance, the researchers assembled an asymmetric supercapacitor pairing the (FeCoMnCuZn)3O4 spinel as the positive electrode with activated carbon as the negative electrode. This architecture is the standard strategy for widening the operating voltage of aqueous supercapacitors: the two electrodes have complementary potential windows, so the full cell can charge and discharge across a combined window without electrolyte decomposition. The device operated stably within a 1.4-volt window and achieved an energy density of 46.94 watt-hours per kilogram at a power density of 750 watts per kilogram. Even when pushed to a punishing 15,000 watts per kilogram, a power level associated with rapid-delivery applications, the device still delivered 12.06 watt-hours per kilogram, demonstrating that the energy advantage does not evaporate at high rates.

Durability, the other half of the practical equation, also held up. After 10,000 charge-discharge cycles at 5 amperes per gram, the asymmetric device retained 85.41 percent of its initial capacitance. For an oxide electrode undergoing repeated Faradaic reactions, where volume changes and dissolution can slowly erode performance, this level of stability reflects the robust spinel framework that high-entropy design provides. The five cations mutually stabilize the lattice, and the structural rigidity of the spinel resists the degradation mechanisms that plague simpler oxides over long cycling campaigns.

What makes this study resonate beyond its impressive numbers is the simplicity of the control lever. Precipitant dosage is a one-line change in a synthesis recipe, requiring no exotic equipment, no templates, and no rare reagents. Yet it dictated phase purity, crystallinity, particle uniformity, elemental distribution, surface valence states, and ultimately device-level energy and power metrics. For a field racing to translate high-entropy oxides from laboratory curiosities into deployable electrode materials, the message is that processing chemistry deserves as much attention as composition itself. The same five-metal formula can be mediocre or outstanding depending on how its precursor is coaxed out of solution.

The broader context is a global push toward energy storage technologies that complement batteries rather than compete with them head-on. Supercapacitors excel where batteries struggle: regenerative braking, grid frequency regulation, backup power for wind turbine pitch systems, and any application demanding rapid charge-discharge cycles and long service life. If high-entropy spinel oxides synthesized by tunable, scalable coprecipitation can keep pushing energy densities upward while preserving cycle lives measured in tens of thousands of cycles, the gap between supercapacitors and batteries will continue to narrow. This work, published in Ionics with a reported energy density approaching 47 watt-hours per kilogram and capacitance retention above 85 percent after 10,000 cycles, suggests that sometimes the most powerful optimization in advanced materials is also the most ordinary: getting the dose right.

Subject of Research: Precipitant-dosage optimization of spinel-type (FeCoMnCuZn)3O4 high-entropy oxide electrodes for asymmetric supercapacitors

Article Title: Precipitant-dosage regulation of spinel-type (FeCoMnCuZn)3O4 high-entropy oxide for high-performance asymmetric supercapacitors

Article References: Tian, Z., Zeng, F., Liang, Y., Zhou, Z., & Xu, B. (2026). Precipitant-dosage regulation of spinel-type (FeCoMnCuZn)3O4 high-entropy oxide for high-performance asymmetric supercapacitors. Ionics. https://doi.org/10.1007/s11581-026-07549-1

Image Credits: AI Generated

DOI: 10.1007/s11581-026-07549-1

Keywords: supercapacitors, high-entropy oxides, spinel structure, coprecipitation, sodium carbonate, asymmetric supercapacitor, electrode materials, energy density, oxygen vacancies, transition metal oxides, energy storage, Dalian Jiaotong University

The study, published in Catalysis Letters, centres on a ternary mixed-metal-oxide catalyst composed of cobalt oxide, ceria and alumina, prepared by a straightforward coprecipitation method. Under optimised conditions, a catalyst with a cobalt-to-cerium-to-aluminium atomic ratio of 1:1:2 delivered 99.9 percent glycerol conversion and 81.3 percent selectivity towards glycidol at 160 degrees Celsius over seven hours, using a glycerol to dimethyl carbonate molar ratio of 1:3 and a catalyst loading of 7 weight percent. For a transesterification reaction run in one pot with a solid catalyst, those figures represent a compelling combination of activity and product control, and they place the system among the more effective heterogeneous formulations reported for this transformation.

Glycidol itself is the reason the result matters. The molecule is the simplest epoxide bearing a hydroxymethyl group, and its strained three-membered oxirane ring makes it exceptionally reactive towards nucleophiles. That reactivity underpins its use in the synthesis of surfactants, epoxy resins, pharmaceutical intermediates, functional polymers and a growing catalogue of fine chemicals. Conventional production routes, however, are far from elegant: they typically rely on multi-step sequences involving halohydrin intermediates, stoichiometric chlorination or dehydrohalogenation, and they generate corrosive salt waste that must be treated downstream. A direct catalytic route from two relatively benign feedstocks, one of them a biodiesel surplus, therefore carries obvious sustainability appeal.

The chemistry linking the feedstocks to the product is a tandem transesterification process. Dimethyl carbonate, often described as a green phosgene substitute, reacts first with one hydroxyl group of glycerol to form glycerol carbonate, a cyclic carbonate intermediate. A second transesterification step then decarboxylates and rearranges this intermediate, expelling methanol and yielding glycidol. Each step demands catalytic functionality: the first benefits from basic sites that activate the glycerol hydroxyl, while the second requires a careful balance of acidic and basic character to promote ring closure without over-decomposing the desired epoxide. Catalysts that lean too far in either direction tend to produce side products such as cyclic carbonate, diglycerol ethers or oligomeric species, which is precisely why selectivity, not merely conversion, has been the stubborn bottleneck.

The Shanghai team’s design philosophy addresses this balance directly by combining three oxides with complementary roles. Cobalt oxide contributes the primary catalytic activity for the transesterification sequence, cerium oxide brings oxygen-storage capacity and redox flexibility along with moderate acid-base sites, and the alumina support provides high surface area together with an abundance of Lewis acidic and basic sites of its own. According to the authors, the alumina component plays a decisive dual role: it enhances the adsorption of both reactants on the catalyst surface and increases the density of surface acidic and basic sites, which in turn improves both the stability and the activity of the final material. In mixed-oxide catalysis, this kind of synergistic division of labour is often what separates a mediocre catalyst from a genuinely practical one.

Characterisation underpinned the mechanistic picture. The researchers deployed a comprehensive analytical arsenal, including X-ray diffraction to confirm crystalline phase formation, infrared spectroscopy to track surface functional groups, thermogravimetric analysis to assess thermal behaviour, ammonia temperature-programmed desorption to quantify acidity, and X-ray photoelectron spectroscopy to probe surface oxidation states and composition. Brunauer-Emmett-Teller and Barrett-Joyner-Halenda measurements characterised surface area and porosity, while scanning electron microscopy revealed morphology. Reaction products were quantified by gas chromatography with flame ionisation detection. Together, these techniques allowed the team to correlate catalytic performance with the acid-base properties of the ternary oxide and to rationalise why the 1:1:2 composition outperformed other formulations tested.

Reaction engineering details matter as much as catalyst design, and the study maps the parameter space carefully. Temperature, reaction time, catalyst loading and the glycerol-to-dimethyl-carbonate ratio were all varied to locate the optimum. At 160 degrees Celsius, the reaction proceeds briskly enough to reach near-quantitative glycerol conversion within seven hours without pushing the epoxide product into secondary reactions that occur at harsher conditions. The threefold excess of dimethyl carbonate serves two purposes: it drives the equilibrium towards products by Le Chatelier’s principle and it suppresses the oligomerisation and etherification pathways that glycerol, with its three reactive hydroxyls, is prone to when it encounters itself on the catalyst surface. The authors also fitted their kinetic data to a Langmuir-Hinshelwood-Hougen-Watson type model, the standard framework for heterogeneous catalysis in which both reactants adsorb on the surface before reacting, consistent with the dual-site mechanism implied by the acid-base characterisation.

The broader context of glycerol valorisation gives the work its urgency. Global biodiesel output continues to expand under renewable fuel mandates, and the associated glycerol glut has depressed prices to the point where crude glycerol is sometimes treated as a disposal problem rather than a commodity. Published reviews, including analyses in Green Chemistry and Current Opinion in Green and Sustainable Chemistry cited by the authors, have catalogued dozens of upgrading strategies, from hydrogenolysis to propanediols, oxidation to dihydroxyacetone, and etherification to fuel additives. Transesterification with dialkyl carbonates stands out among these because it uses a non-toxic reagent, produces methanol as the only coproduct, and can in principle be run with recyclable solid catalysts, avoiding the neutralisation and separation burdens that homogeneous bases impose.

Previous heterogeneous attempts at this reaction illustrate the challenge the new catalyst overcomes. Studies in Catalysis Science and Technology, ACS Sustainable Chemistry and Engineering and Molecular Catalysis have examined hydrotalcites, modified zeolites, supported ionic liquids and various metal oxides, with each formulation trading conversion against selectivity in familiar ways. Strongly basic catalysts accelerate carbonate formation but struggle with the subsequent step to glycidol; strongly acidic systems promote polymerisation. The ternary Co3O4/CeO2/Al2O3 system, by embedding moderate acid and base sites in close proximity on a thermally robust support, appears to thread this needle, and the authors frame the work explicitly as offering design insights for mixed-metal-oxide catalysts aimed at glycidol synthesis.

There are, of course, the usual caveats that attend a laboratory-scale catalysis study before industrial translation. Long-term catalyst lifetime under continuous operation, tolerance to the water and methanol impurities present in crude biodiesel-derived glycerol, ease of regeneration and performance at larger scale all remain to be demonstrated, and the published report does not address them. Nevertheless, the headline numbers speak for themselves: essentially complete conversion of a waste-stream feedstock, four-fifths selectivity to a molecule worth orders of magnitude more per kilogram than the glycerol it came from, achieved with a solid catalyst made by simple coprecipitation from inexpensive metal salts. As the chemical industry intensifies its search for processes that convert surplus biomass-derived streams into platform chemicals, this ternary oxide offers a template worth copying, and it adds a persuasive new entry to the growing evidence that clever catalyst architecture can turn biodiesel’s most awkward by-product into a genuine opportunity.

Subject of Research: Heterogeneous catalytic one-pot synthesis of glycidol from glycerol and dimethyl carbonate over a Co3O4/CeO2/Al2O3 mixed-metal-oxide catalyst

Article Title: One-Pot Synthesis of Glycidol from Glycerol and Dimethyl Carbonate Over Co3O4/CeO2/Al2O3 Catalyst

Article References: Zhou, X., Zhang, L., Lin, S., Tang, M., Guo, P., Li, K., Vinogradov, J., & Lu, J. (2026). One-Pot Synthesis of Glycidol from Glycerol and Dimethyl Carbonate Over Co3O4/CeO2/Al2O3 Catalyst. Catalysis Letters, 156(9), Article 267. https://doi.org/10.1007/s10562-026-05518-x

Image Credits: AI Generated

DOI: 10.1007/s10562-026-05518-x

Keywords: glycidol, glycerol, dimethyl carbonate, transesterification, mixed metal oxide catalyst, cobalt oxide, ceria, alumina, biodiesel by-product valorization, heterogeneous catalysis, green chemistry, coprecipitation