Oxidative desulfurization has emerged as one of the most promising candidates. Instead of hydrogenating sulfur out of the fuel, the process converts sulfur atoms into their oxidized forms, typically sulfoxides and sulfones, which are far more polar than the parent fuel molecules. Once oxidized, they can be pulled out of the hydrocarbon mixture by simple extraction, adsorption, or distillation. The catch is the oxidant. Many laboratory demonstrations rely on hydrogen peroxide or other powerful oxidizing agents that are costly, hazardous to store, and add their own environmental burden. The dream scenario, long pursued by catalysis researchers, is to use molecular oxygen from ordinary air as the terminal oxidant, since air is free, abundant, and leaves no residue. The difficulty is that molecular oxygen is kinetically inert, and activating it efficiently at mild conditions requires precisely engineered catalytic sites.

A new study published in Catalysis Letters by Xi Liu, Wenjian Wu, Ran Wang, Rongkang Li, Yafei Li, Jie Hou, Fuquan Xiao, and Linhua Zhu, spanning Hainan Normal University and China Lesso Group Holdings Limited, reports a catalyst design that achieves exactly this goal. The team prepared a composite material in which molybdenum trioxide and copper oxide grow together symbiotically, forming what they call a MoO3@CuxO heterointerface. When tested in aerobic catalytic oxidative desulfurization under an air atmosphere, the composite achieved complete, one hundred percent desulfurization of aromatic sulfur compounds within five hours. The result is striking not merely for the number itself, but for the mechanism behind it, which hinges on active sites that exist in neither of the parent oxides alone.

The central concept of the work is heterointerface engineering, a catalyst design strategy built on the symbiotic growth of two different metal oxides. When two oxides are forced into intimate contact at the nanoscale, the boundary region between them is no longer simply the sum of its parts. Electronic structure is perturbed, surface properties change, and, most importantly for catalysis, entirely new types of active centers can appear that are unavailable in either individual oxide. In the MoO3@CuxO system, the researchers found that bringing molybdenum trioxide and copper oxide into symbiosis generated abundant low-valence copper sites, formally Cu+, along with a high density of lattice defects at the interface. Neither pure MoO3 nor pure CuO provides these features on its own; they are emergent properties of the junction between the two materials.

Why would Cu+ sites matter so much for activating oxygen? The answer lies in the electronic configuration of copper. Low-valence copper can donate an electron to molecular oxygen, reducing O2 to the superoxide radical anion, a reactive oxygen species with enough oxidizing power to attack sulfur atoms in organic molecules. This electron-transfer chemistry is well documented for copper complexes in solution, where Cu–O2 and Cu2–O2 intermediates have been studied extensively, but creating stable, abundant Cu+ sites on a solid heterogeneous catalyst is far more challenging. In ordinary copper oxide, copper sits in the +2 state, and the material lacks the redox flexibility needed to cycle electrons into oxygen efficiently. The heterointerface changes that picture, stabilizing Cu+ species and endowing the surface with enhanced redox properties that the individual oxides cannot match.

The defective interface plays a supporting but essential role. Lattice defects, such as oxygen vacancies and coordination-unsaturated sites, are widely recognized in catalysis research as hotspots for reactivity. They can adsorb and activate small molecules, facilitate electron transfer, and lower the energy barriers of key elementary steps. In the MoO3@CuxO composite, the symbiotic growth process creates a defect-rich boundary region that is more favorable for catalytic reactions than the smooth surfaces of the individual oxides. Together, the Cu+ sites and the defective interface form a cooperative system: the copper sites activate molecular oxygen into superoxide radicals, while the surrounding defect landscape supports the surface redox cycling that keeps the catalytic turnover going.

Catalytic testing validated the design at every step. The composite removed one hundred percent of aromatic sulfur compounds from the fuel under an air atmosphere within five hours, a level of performance that qualifies as deep desulfurization by any standard. The aromatic sulfur compounds targeted in such studies, including dibenzothiophene and its derivatives, are precisely the species that hydrodesulfurization handles worst, which makes the result directly relevant to the refining industry’s most persistent challenge. The use of air as the oxidant is the headline feature: no hydrogen peroxide, no pressurized oxygen, no stoichiometric chemical oxidants, just the oxygen already present in the atmosphere above the reaction mixture.

The broader significance of the study lies in its demonstration of a general strategy rather than a one-off material. By rationally choosing two metal oxides whose interaction generates the desired active sites, catalyst designers can in principle create functionality that no single-component material offers. The authors emphasize that this approach highlights the pivotal role of heterointerface engineering in catalytic oxidation and offers an effective blueprint for designing oxidative desulfurization catalysts. Similar logic has been applied in neighboring fields, from copper-ceria catalysts for carbon monoxide oxidation, where oxygen vacancies and Cu+ species are also decisive, to mixed-oxide heterostructures that boost selective oxidation of hydrocarbons. The MoO3@CuxO work adds fuel desulfurization to the growing list of reactions where the interface, not the bulk, is where the chemistry happens.

For the energy transition, the implications are worth considering carefully. Even as electric vehicles displace combustion engines in passenger transport, heavy-duty shipping, aviation, and industrial sectors will continue to rely on liquid fuels for decades, and every ton of sulfur those fuels contain becomes an atmospheric burden. Reviews of desulfurization technology note a global drive toward cleaner fuels and net-zero emissions, with oxidative desulfurization repeatedly identified as a key complementary technology to conventional hydrotreating. A catalyst that works with air at mild conditions could reduce the energy intensity and capital cost of deep desulfurization, particularly for refineries processing high-sulfur feedstocks or for distributed fuel-cleaning applications where hydrogen infrastructure is unavailable.

There are, of course, the usual caveats that separate a laboratory milestone from an industrial process. Real fuels contain a complex matrix of nitrogen compounds, olefins, and aromatics that can compete for active sites or poison the catalyst, and long-term stability, recyclability, and scale-up of the symbiotic growth synthesis remain to be demonstrated at refinery scale. The data supporting the study, available from the corresponding author upon reasonable request, and the research, funded by the Hainan Province International Science and Technology Cooperative Research and Development Project and the Natural Science Foundation of Hainan Province, provide the foundation for those next steps. What the Catalysis Letters paper delivers now is a proof of concept with real force: that the deliberate marriage of two ordinary metal oxides can conjure active sites that neither possesses alone, and that those sites are powerful enough to turn the air itself into the reagent that cleans our fuels. In the quiet arithmetic of catalysis, where every percentage point of conversion and every avoided chemical input matters, that is a result worth celebrating.

Subject of Research: Heterointerface engineering of MoO3@CuxO catalysts for aerobic oxidative desulfurization of fuels

Article Title: Defect-Rich MoO3@CuxO Heterointerface with Abundant Cu+ Active Sites for Efficient Aerobic Oxidative Desulfurization

Article References: Liu, X., Wu, W., Wang, R., Li, R., Li, Y., Hou, J., Xiao, F., & Zhu, L. (2026). Defect-Rich MoO3@CuxO Heterointerface with Abundant Cu+ Active Sites for Efficient Aerobic Oxidative Desulfurization. Catalysis Letters, 156(10), Article 292. https://doi.org/10.1007/s10562-026-05533-y

Image Credits: AI Generated

DOI: 10.1007/s10562-026-05533-y

Keywords: heterointerface engineering, oxidative desulfurization, Cu+ active sites, molybdenum trioxide, copper oxide, superoxide radicals, lattice defects, aerobic oxidation, fuel refining, heterogeneous catalysis, air oxidant, aromatic sulfur compounds

The central challenge the team set out to address concerns scalability and flexibility in ionic neuromorphic devices. Neuromorphic nanofluidics, which harness ionic rather than electronic transport to emulate neural dynamics, have generally depended on nanoconfinement—squeezing ionic motion into channels with dimensions comparable to the electrical double layers that form at solid-liquid interfaces. This confinement gives researchers exquisite control over how quickly ions accumulate, dissipate, and relax, which in turn determines whether a device exhibits the short-term and long-term memory effects characteristic of biological synapses. But the inherent scales of the spatial interactions at nanoconfined interfaces impose hard limits: fabricating angstrom-scale or nanometer-scale channels across large areas is difficult, integrating them into soft, stretchable, or biologically coupled systems is harder still, and the spatial scale of the governing physics cannot easily be tuned after fabrication.

The new system sidesteps nanoconfinement altogether by introducing what the researchers call cascaded-heterointerfacial ion traps within a multiphasic gel ion transporter, or GIT. Rather than a single confining channel, the device consists of multiple gel phases joined at heterointerfaces—boundaries between chemically distinct soft phases with differing ionic environments. When ions attempt to cross these interfaces, they encounter what the authors describe as interionic hierarchical cross-interface retardation and dissipation. In practical terms, the coupled dynamics of ion accumulation, crowding, and relaxation on either side of each boundary slow and scatter ionic flux in a hierarchy of timescales. Each interface therefore behaves like a trap: it can hold ionic charge transiently, release it gradually, and modulate the transmission of subsequent ionic spikes. By cascading several such interfaces in series, the system multiplies these trapping effects, creating rich temporal dynamics from macroscopically scalable soft materials.

One of the clearest signatures of this design is a pronounced ionic bipolar rectification effect, with rectification ratios exceeding one thousand. Rectification means that ionic current flows far more readily in one polarity than the other, analogous to the behavior of a diode in an electronic circuit. In biological terms, it resembles the one-way gating of signals at synapses and ion channels. Achieving ratios above 10^3 in an entirely soft, gel-based architecture indicates that the cascaded traps do not merely attenuate signals but actively sculpt their directionality. The rectification arises because ion enrichment and depletion at successive heterointerfaces depend strongly on the polarity of the applied bias, so the same physical structure can either promote or suppress transmission depending on which way the ionic spike travels through the system.

Beyond directionality, the device exhibits what the researchers characterize as spike-strength-dependent and timing-dependent dual-order plasticity. This is a cornerstone of neural computation. In the brain, synapses strengthen or weaken depending both on how strongly they are activated and on the precise relative timing of pre- and postsynaptic spikes—a phenomenon known as spike-timing-dependent plasticity, which is widely believed to underpin learning and memory formation. By reproducing both amplitude-dependent and timing-dependent forms of plasticity within a single ionic platform, the cascaded-heterointerface system captures two distinct but intertwined orders of synaptic adaptability. The interionic retardation and dissipation at each trap accumulate across the cascade, so the device’s response to any given spike depends on its own recent history—exactly the property that distinguishes a memristive, memory-bearing element from a passive conductor.

Particularly significant is the integration of both short-term and long-term memory effects within the same material system. Short-term plasticity, in which synaptic efficacy transiently changes over milliseconds to seconds, enables computational functions such as filtering, adaptation to stimulus statistics, and temporal differentiation. Long-term plasticity, persisting over much longer durations, provides the substrate for durable memory and learned associations. Biological synapses blend the two seamlessly, and neuromorphic engineers have long struggled to replicate that blend with adequate dynamic range. The hierarchical trapping timescales of the multiphasic gel naturally generate both regimes, allowing the team to demonstrate complex ion-based synaptic adaptability and multiple biologically grounded learning rules, including forms of spike-timing-dependent behavior implemented through purely ionic dynamics.

The energy figures reported are remarkable for a soft material system: multistate ionic neuromorphic processing at as little as 0.61 picojoules per spike. For context, individual synaptic transmission events in the human brain are often estimated to consume on the order of tens of femtojoules to picojoules, and modern semiconductor-based artificial synapses frequently require far more energy per operation, particularly when overheads of converting signals between electronic and ionic or chemical domains are counted. Operating in the picojoule regime means the gel system is not merely a conceptual demonstration but approaches the energy budgets at which practical, body-attached, or even body-implanted neuromorphic hardware becomes feasible. Soft matter also offers mechanical compliance and chemical compatibility that silicon cannot match, which points directly toward the study’s most eye-catching experiment.

That experiment involved creating a biohybrid neural circuit by interfacing the in vivo neuro-iontronic processor with the transected sciatic nerve of a rat. The sciatic nerve, the major peripheral nerve running down the hind limb, was cut and the processor was connected across the transection, allowing nerve-generated spikes to drive ionic processing in the gel and, reciprocally, allowing the processor’s output to stimulate downstream nerve segments. The result was bioneuron-driven ionic neuromorphic processing: the device’s synaptic states were updated by genuine biological action potentials, and in turn the device reconfigured the interneural signals passing through the injured nerve. The experiment, approved by the Animal Protection Ethics Committee of Capital Medical University, suggests a route toward prosthetic or regenerative interfaces in which a soft computational material does not simply relay nerve signals but adaptively reshapes them according to neuromorphic learning rules.

The theoretical underpinnings of the system were developed in parallel with the experiments, with collaborators at Tsinghua University performing calculations that connect the observed macroscopic behavior to the microscopic interionic dynamics at each heterointerface. This modeling work clarifies how hierarchical cross-interface retardation and dissipation give rise to the device’s memristive characteristics and provides a design framework for tuning trap strength, cascade depth, and phase chemistry. The work builds on a rapidly maturing field of iontronics and nanofluidic computing, in which recent years have seen fluidic memristors, droplet-based modular iontronics, and mechano-ionic logic switches emerge from laboratories around the world. What distinguishes the present contribution is the deliberate move away from spatial confinement as the sole control lever and toward interfacial design in soft, multiphasic matter—a shift that promises devices that are cheaper to fabricate, easier to scale, and far more amenable to integration with living tissue.

The implications extend across several frontiers. For brain-inspired computing, the system offers a hardware substrate in which the informational carriers, the physical dynamics, and the material compliance all resemble biology far more closely than conventional transistors do, potentially enabling machine learning implementations that exploit the same temporal plasticity principles the brain uses. For medicine, a soft iontronic processor that can learn from and modulate peripheral nerve activity hints at adaptive neural prostheses, smart neuro-repair scaffolds, and closed-loop bioelectronic therapies that reconfigure damaged signaling pathways in real time. And for the broader materials community, the demonstration that cascaded heterointerfaces can substitute for nanoconfinement opens a design space in which chemistry, phase architecture, and interfacial engineering replace lithographic miniaturization. Much work remains before such devices leave the laboratory—long-term biostability, manufacturing reproducibility, and integration with clinical hardware all present substantial hurdles—but the convergence of picojoule energy consumption, dual-order synaptic plasticity, and verified in vivo biohybrid operation marks a genuinely notable step toward computing materials that think the way biology does.

The choice of gel-based ion transporters also reflects a broader trend in which soft ionic conductors are increasingly viewed as viable active materials rather than passive wiring. Because ions are the native charge carriers of living systems, devices that process signals ionically can, in principle, couple to tissue without the transduction penalties that arise when electronic implants must convert ionic bioelectricity into electron flow and back again. The multiphasic architecture takes advantage of this by letting phase chemistry, rather than channel geometry, define the functional behavior, which means trap dynamics can in principle be tuned through material formulation.

The dual-order plasticity reported here is also notable from a computational standpoint. Spike-strength dependence and timing dependence together enable learning rules that resemble Hebbian and predictive forms of adaptation studied in neuroscience, and memristive hardware implementing such rules has been proposed as a route to energy-efficient spatiotemporal learning. Demonstrating both orders of plasticity in a purely ionic, soft-matter platform suggests that such rules need not depend on solid-state electronics.

The in vivo sciatic nerve experiment, conducted under ethics approval AEEI-2025-036, additionally illustrates how a processor driven by genuine biological action potentials could serve as a testbed for studying signal reconfiguration in injured nerves, complementing conventional cuff electrodes and stimulation implants.

Subject of Research: Soft-matter iontronic devices using cascaded-heterointerface ion traps for multistate ionic neuromorphic processing and biohybrid neural interfacing.

Article Title: Soft-matter multistate ionic neuromorphic processing based on cascaded-heterointerface ion traps

Article References: Wu, Z., Zhang, S., Zhai, L., Zhang, A., Zhu, X., Xu, J., Liu, H., Xu, Z., Jiang, L., & Zhao, Z. (2026). Soft-matter multistate ionic neuromorphic processing based on cascaded-heterointerface ion traps. Nature Electronics. https://doi.org/10.1038/s41928-026-01688-z

Image Credits: AI Generated

DOI: 10.1038/s41928-026-01688-z

Keywords: neuromorphic computing, iontronics, soft matter, ionic memory, synaptic plasticity, nanofluidics, biohybrid circuits, gel ion transporter, ion traps, energy-efficient computing, neural interfaces, Nature Electronics

Yet conventional EMW absorbers often face a structural trade-off. Carbon-rich systems can reflect waves too efficiently, preventing deep penetration, while metal-based materials can suffer from impedance mismatch, limiting how effectively energy is dissipated. In practical terms, a successful absorber must both “invite” waves in and ensure they are ultimately consumed inside the material.

A research team from Qingdao University addresses this problem with a “heterointerface–defect synergy” strategy. They used solvothermal-electrospinning methods to couple bimetallic sulfides—CoS₂ and NiS₂—with hollow carbon nanofibers (HCNFs), building a composite engineered for a gradient electronic structure that promotes energy loss pathways.

The key mechanism begins at the CoS₂/NiS₂ heterointerface. There, a strong built-in electric field forms, promoting directional charge transfer. This field accelerates conversion of EMW energy into thermal dissipation through polarization and interfacial charge dynamics.

To further intensify losses, the design introduces sulfur vacancies that act as “energy traps.” These defect sites interact with the built-in electric field, strengthening dipole polarization and improving the coupling between structural imperfections and electromagnetic energy.

Meanwhile, the three-dimensional hollow network of HCNFs supports more effective impedance matching and increases the effective propagation length of waves within the absorber. Together, these features enhance multiple reflections and scattering, giving waves more opportunities to be attenuated.

Performance results are striking. At a thickness of 2.6 mm, the effective absorption bandwidth (EAB) spans 8.32–18.4 GHz, covering the full X-band and Ku-band. At 2.4 mm, the minimum reflection loss (RLmin) reaches −48.04 dB, corresponding to absorption of over 99.99% of incident EMW energy.

Compared with single-metal sulfide systems, the EAB increases by 61%. Importantly for real-world deployment, the material maintains excellent absorption even at a low filler loading of 15 wt% under 60° oblique incidence.

The findings were published in Nano Research on 14 May 2026, offering a lightweight, broadband, and highly lossy platform that could support next-generation shielding for civilian electronics and potentially improve stealth-relevant radar mitigation technologies.

Subject of Research: Heterointerface Engineering of Bimetallic Sulfides Enhances Polarization Loss for Superior Electromagnetic Wave Absorption Performance
Article Title: Heterointerface Engineering of Bimetallic Sulfides Enhances Polarization Loss for Superior Electromagnetic Wave Absorption Performance
News Publication Date: 14-May-2026
Web References: http://dx.doi.org/10.26599/NR.2026.94908411
References: Nano Research (14-May-2026); DOI: 10.26599/NR.2026.94908411
Image Credits: Credit: Nano Research, Tsinghua University Press

Keywords

bimetallic sulfides; heterointerface engineering; sulfur vacancies; hollow carbon nanofibers; built-in electric field; polarization loss; electromagnetic wave absorption