The study, published in the Journal of Materials Science by Shuai Zou, Xiaoyu Song, Yaohang Gu, Xiaoyan Zhang, and Xiwei Qi, centers on sodium niobate, NaNbO3, a perovskite ceramic that has emerged as one of the most promising lead-free candidates for dielectric energy storage. Sodium niobate is attractive for several reasons. It is environmentally benign, it exhibits antiferroelectric-like behavior in which neighboring electric dipoles point in opposite directions, and it can deliver high recoverable energy density with excellent charge-discharge performance. When an electric field is applied, those anti-aligned dipoles can be coerced into alignment, and when the field is removed they snap back, releasing stored energy quickly and with minimal loss. That snap-back is precisely what a pulsed power capacitor needs.

But sodium niobate has a stubborn weakness that has kept it out of real-world products: thermal instability. The material undergoes a series of structural phase transitions as temperature changes, and each transition shifts its dielectric response. In practical terms, the capacitance of pure NaNbO3 varies by more than 50 percent across the temperature window from minus 50 to plus 150 degrees Celsius, a swing far too large for commercial electronics, which typically demand that capacitance stay within 15 percent of its room-temperature value. A capacitor that drifts wildly as a device heats up or cools down cannot be trusted in an automotive engine bay, an aircraft avionics bay, or even a laptop that warms under load.

The team’s solution draws on one of the hottest ideas in modern materials science: high-entropy design. Rather than doping sodium niobate with a single additive, the researchers composited it with a five-component rare-earth modified bismuth ferrite, (Bi0.2La0.2Y0.2Dy0.2Tb0.2)FeO3, abbreviated BLYDTF. In this phase, five different cations share the same crystallographic site in nearly equal proportions, creating a chemically disordered lattice in which no single element dominates. High-entropy oxides of this kind were first demonstrated a decade ago, and they have since been shown to flatten temperature-dependent properties, because the disorder smears out the sharp phase transitions that plague conventional compounds. Bismuth ferrite itself brings a very high Curie temperature, meaning its ferroelectric ordering persists to extremely high temperatures, providing a thermally robust backbone for the composite.

The researchers synthesized a series of ceramics with the general formula (1-x)NaNbO3-xBLYDTF, where x ranged from 0 to 0.15, and systematically evaluated their energy storage behavior. The results were striking. The optimized composition achieved a recoverable energy density of approximately 4.1 joules per cubic centimeter at an electric field strength of 510 kilovolts per centimeter. To put that number in perspective, recoverable energy density is the figure of merit that determines how much usable energy a capacitor can deliver per charge cycle, and values above 4 joules per cubic centimeter in a lead-free bulk ceramic place this material firmly among the competitive candidates for next-generation pulsed power capacitors.

Speed matters just as much as capacity, and here the material truly shines. The researchers measured a discharge time constant, denoted t0.9, of only 40 nanoseconds, meaning the ceramic can release 90 percent of its stored energy in 40 billionths of a second. That kind of ultr fast discharge is essential for pulsed power applications such as electromagnetic launchers, high-power microwave sources, defibrillators, and precision laser systems, where energy must be dumped almost instantaneously. Slow capacitors simply cannot serve these roles, no matter how much energy they hold. The combination of high density and nanosecond-scale release in a lead-free, thermally stable package is what makes this work notable.

The temperature stability results are arguably the headline achievement. The temperature coefficient of capacitance, or TCC, quantifies how much capacitance drifts as temperature changes, and industrial specifications known as EIA codes define acceptable limits. The X7R designation, one of the most widely used standards in the capacitor industry, requires capacitance to remain within plus or minus 15 percent of its 25-degree-Celsius value across the range from minus 55 to plus 125 degrees Celsius. The composite ceramic developed by the team fully satisfies the X7R specification, a milestone that pure sodium niobate cannot approach. Meeting X7R means the material is no longer a laboratory curiosity but a genuine candidate for multilayer ceramic capacitor manufacturing, where X7R-class dielectrics dominate the mid-capacitance market.

Underlying these headline numbers is a subtle microstructural story. Introducing the high-entropy bismuth ferrite phase into the sodium niobate matrix disrupts the long-range antiferroelectric order of the host, breaking large domains into smaller polar regions and introducing local random fields that make the material behave more like a relaxor ferroelectric. Relaxors respond to electric fields with slim, low-loss hysteresis loops, which means less energy is wasted as heat during each charge-discharge cycle and more of the stored energy is actually recoverable. The chemical disorder also tends to improve breakdown strength, since randomly distributed local structures impede the growth of the conductive pathways that lead to catastrophic dielectric failure at high fields. The 510 kilovolts per centimeter field the material withstands reflects that improvement directly, because recoverable energy density scales with the square of breakdown field.

The broader significance of the work lies in its design philosophy. Instead of searching for a single magic composition, the team combined two complementary strategies: a lead-free antiferroelectric host with intrinsically high energy storage potential, and an entropy-stabilized partner phase that suppresses thermal drift while introducing beneficial polar disorder. This compositing approach, sometimes described as high-entropy modulation of a conventional ferroelectric, has gained momentum across the field, with recent studies in Science and Nature Materials reporting ultrahigh energy storage in entropy-engineered ceramic capacitors. The present work extends that strategy to the sodium niobate family specifically with an eye on industrial temperature standards, bridging the gap between record-setting laboratory results and the reliability requirements of commercial components.

Challenges remain before such ceramics reach production. Multilayer capacitor manufacturing requires co-firing the dielectric with inexpensive base-metal electrodes at controlled temperatures, and the long-term reliability, fatigue behavior, and scalability of high-entropy composites must be validated under industrial conditions. Nevertheless, the demonstration that a lead-free sodium niobate-based ceramic can simultaneously deliver roughly 4.1 joules per cubic centimeter of recoverable energy, 40-nanosecond discharge, and full X7R compliance marks a meaningful step toward capacitors that are simultaneously powerful, fast, tough, and free of toxic lead. As portable electronics proliferate and pulsed power systems multiply, materials like this one may quietly become the unsung workhorses of the electrified world.

Subject of Research: Lead-free NaNbO3-based high-entropy composite dielectric ceramics for temperature-stable capacitive energy storage

Article Title: Design of an X7R-type NaNbO3-based energy storage ceramic by compositing with (Bi0.2La0.2Y0.2Dy0.2Tb0.2)FeO3

Article References: Zou, S., Song, X., Gu, Y., Zhang, X., & Qi, X. (2026). Design of an X7R-type NaNbO3-based energy storage ceramic by compositing with (Bi0.2La0.2Y0.2Dy0.2Tb0.2)FeO3. Journal of Materials Science. https://doi.org/10.1007/s10853-026-13641-8

Image Credits: AI Generated

DOI: 10.1007/s10853-026-13641-8

Keywords: sodium niobate, NaNbO3, energy storage ceramics, dielectric capacitors, high-entropy materials, bismuth ferrite, X7R standard, lead-free perovskites, relaxor ferroelectrics, pulsed power, temperature stability, recoverable energy density

To understand why the result matters, it helps to look closely at the architecture of an inverted perovskite solar cell. In this configuration, light enters through a transparent electrode and first encounters a hole-selective layer that extracts positive charge carriers from the perovskite absorber. In state-of-the-art devices, that layer is typically a self-assembled monolayer: a single molecular layer in which each molecule anchors to the oxide substrate through a phosphonic acid group and presents an energy-aligned frontier orbital to the perovskite above. These monolayers use vanishingly small amounts of material, coat rough surfaces uniformly, and have been central to the efficiency surge of recent years. But they carry a structural vulnerability. A monolayer built from a single molecular species tends to pack into one dominant motif, and when that motif is stressed, by heat, by mechanical strain, or by the chemical pressure of the perovskite crystallizing on top of it, the packing can collapse. When the packing collapses, the pathways that holes use to hop from the perovskite into the electrode are disrupted, and the device begins to degrade.

The Hong Kong-led team, including co-first authors Deng Wang, Mingqian Chen and Jiacong Feng, attacked this vulnerability by mixing three carbazole-naphthalene self-assembled molecules that share similar chemical skeletons but differ in their intermolecular interactions and packing preferences. The strategy mirrors the high-entropy concept that transformed alloy design, where mixing multiple elements in near-equimolar ratios stabilizes materials through configurational entropy rather than through a single dominant crystal structure. Here, the entropy is not in atomic positions but in packing modes. Because each of the three molecules prefers a slightly different way of stacking against its neighbors, the blended film cannot settle into one brittle, long-range-ordered arrangement. Instead, it forms a dense mosaic of coexisting packing motifs, a high-entropy system in which no single failure mode can propagate easily. The result is a contact that extracts holes efficiently while remaining remarkably resilient under external stress.

Proving that such a high-entropy molecular contact actually forms, rather than simply producing a phase-separated mess, required a battery of complementary techniques. Single-crystal analysis of the individual molecules revealed the distinct intermolecular interactions, hydrogen bonding patterns and π-stacking geometries that each species brings to the blend. Molecular dynamics simulations, run on the blended films, showed how the three components interpenetrate and how the resulting diversity of local environments suppresses the large-scale structural rearrangements that plague single-component monolayers. Interfacial characterizations of the actual devices then confirmed that the mixed contact maintains intimate, robust contact with the perovskite layer. Together, these measurements painted a consistent picture: the ternary blend does not segregate or compete, it cooperates, producing an interface whose structural heterogeneity is precisely the source of its mechanical and thermal toughness.

The charge-transport consequences of that heterogeneity are subtle but favorable. In an idealized, perfectly ordered monolayer, holes move through well-defined electronic coupling pathways between adjacent molecules. Disorder might seem like the enemy of such transport, and in amorphous organic semiconductors it often is. But the high-entropy contact occupies a sweet spot: the three molecules are chemically similar enough that their energy levels remain aligned, so no deep traps are introduced, while their diverse packing modes create multiple, redundant percolation pathways for hole extraction. Transient absorption spectroscopy measurements on the devices supported this picture, showing efficient hole transfer at the contact. In effect, the team traded a single elegant highway for a dense network of smaller roads, and the network proved far harder to knock out. The approach also echoes recent work on high-entropy hybrid perovskites, in which disordered organic moieties within the perovskite lattice itself have been shown to enhance stability, suggesting a broader design principle spreading across the field.

The photovoltaic numbers place the devices at the very front of the inverted perovskite pack. The champion cell delivered a power conversion efficiency of 27.50 percent, and an independent certified steady-state efficiency of 27.31 percent was recorded, a figure that stands among the highest reported for single-junction perovskite devices and compares favorably with entries on established efficiency charts. Efficiency alone, however, has never been the bottleneck for perovskite commercialization; stability has. Here the high-entropy contact earned its keep. Under maximum power point tracking at 85 degrees Celsius in ambient air, a punishing accelerated-ageing protocol that combines thermal stress, continuous illumination and electrical bias, the devices retained essentially all of their initial efficiency after 1,300 hours. The team also reported extended stability under a range of other accelerated ageing tests, consistent with the consensus ISOS procedures that the perovskite community uses to standardize stability reporting.

That combination of certified efficiency and heat tolerance addresses the two criteria that investors and module manufacturers scrutinize most closely. Perovskite modules must survive decades of outdoor service, during which rooftop temperatures can exceed 70 degrees Celsius in summer and internal junctions run hotter still. A contact layer that structurally collapses under such thermal load becomes a device-wide liability, initiating delamination and accelerating the decomposition of the perovskite itself. By hardening the molecular interface at its weakest scale, the single molecular layer, the high-entropy strategy protects the entire stack. The fact that the improvement required no exotic materials, only a ternary blend of closely related carbazole-based molecules that can be deposited from solution, makes the approach attractive for scalable manufacturing, where process simplicity and material cost weigh as heavily as laboratory performance.

The authors emphasize that the framework is broadly applicable beyond the specific molecules they synthesized. The underlying principle, that blending species with similar electronic structures but distinct packing motifs generates entropy-stabilized interfaces, could in principle be applied to electron-selective contacts, to the buried interfaces of tandem devices, and to other solution-processed thin-film technologies that rely on self-assembled monolayers, including organic electronics and emerging tandem architectures that pair perovskites with silicon. Recent parallel reports of ternary self-assembled molecular contacts for perovskite-silicon tandems and of entropy-regulating molecular locks that stabilize the perovskite lattice indicate that high-entropy thinking is rapidly spreading through molecular-level photovoltaic engineering. The present work adds a rigorous structural and mechanistic foundation to that trend, linking single-crystal chemistry, molecular simulation and device-level certification in a single coherent study.

Challenges remain before high-entropy contacts reach the factory floor. The long-term behavior of ternary blends over years rather than months, their behavior in full-size modules with large areas and interconnects, and the reproducibility of blend stoichiometry in industrial coating processes will all need to be demonstrated. Yet the conceptual shift is hard to overstate. For years, interfacial engineering in perovskite solar cells has pursued purity and order, one molecule, one packing mode, one optimized monolayer. This study demonstrates that controlled multiplicity can outperform perfection, converting the very disorder that engineers once feared into a shield against degradation. If the high-entropy design rule generalizes as broadly as the authors suggest, the molecular interfaces of future solar cells may look less like crystalline lattices and more like entropy-toughened mosaics, quietly extracting charge under a blazing sun for decades without complaint.

Subject of Research: High-entropy molecular hole-selective contacts for efficient and stable inverted perovskite solar cells

Article Title: High-entropy molecular contacts enable high-efficiency and stable perovskite solar cells

Article References: Wang, D., Chen, M., Feng, J., Li, Q., Wong, C.-T., Lei, G., Jiang, Q., Wang, T., Jiang, W., & Jen, A. K.-Y. (2026). High-entropy molecular contacts enable high-efficiency and stable perovskite solar cells. Nature Photonics. https://doi.org/10.1038/s41566-026-02028-5

Image Credits: AI Generated

DOI: 10.1038/s41566-026-02028-5

Keywords: perovskite solar cells, self-assembled monolayers, high-entropy materials, hole-selective contacts, power conversion efficiency, operational stability, molecular packing, inverted architecture, charge transport, molecular dynamics simulations, thermal ageing, Nature Photonics

The thermodynamics of water splitting look deceptively simple. Whether the electrolyte is acidic or alkaline, the minimum cell voltage needed to drive the reaction is 1.23 volts. In practice, electrolyzers demand considerably more, because the OER is a four-electron, multi-step process riddled with energy barriers, whereas the hydrogen evolution reaction at the cathode is a comparatively easy two-electron affair. That extra voltage, the overpotential, is pure waste heat and lost efficiency. In acidic systems, proton exchange membranes deliver low resistance and high gas purity, but the corrosive environment forces the use of scarce, expensive iridium and ruthenium oxides at the anode. Alkaline electrolysis, by contrast, opens the door to first-row transition metals that cost a fraction as much and can match, or even exceed, the performance of precious metal systems.

Understanding why the OER is so sluggish begins with its mechanism. The dominant framework, the adsorbate evolution mechanism, describes a sequence in which hydroxide species adsorb onto metal sites, convert into oxygen intermediates, and ultimately release molecular oxygen. Each step carries a Gibbs free energy cost, and the largest one sets the rate-determining step and thus the overpotential. The problem is that the adsorption energies of the intermediates are not independent. Because the *OOH and *OH species bind to the surface through a single oxygen atom, their energies scale linearly across virtually all oxide surfaces. The difference between the oxygen and hydroxide binding energies, roughly 3.2 electron volts on average, cannot be compressed below about 1.6 electron volts, while an ideal catalyst would need only 1.23. That mismatch imposes a theoretical overpotential floor of roughly 0.37 electron volts, and it turns catalyst design into a game of climbing a volcano-shaped activity plot, where the sweet spot lies at neither too strong nor too weak oxygen binding.

Some catalysts, however, refuse to obey the volcano. Their activity exceeds what the scaling relationship permits, and their kinetics shift with electrolyte pH in ways the adsorbate mechanism cannot explain. The resolution is the lattice oxygen mechanism, in which oxygen atoms belonging to the catalyst’s own crystal lattice participate directly in forming the O–O bond, bypassing the hydroperoxide intermediate entirely. The evidence is compelling: when researchers label lattice oxygen with the isotope oxygen-18 and run the reaction in an oxygen-16 electrolyte, differential electrochemical mass spectrometry detects mixed isotopic oxygen molecules, proof that lattice oxygen is being released as product gas. The mechanism is favored when the metal–oxygen bond is highly covalent, which is governed by the position of the oxygen 2p band relative to the metal 3d band. Raising the oxygen p-band center toward the Fermi level activates oxygen redox chemistry, promotes vacancy formation, and unlocks the lattice oxygen pathway, offering a route around the scaling-relation ceiling.

Armed with these mechanistic insights, catalyst designers have developed a toolkit of activity descriptors that predict performance without simulating every reaction step. Beyond the oxygen binding energy difference, the d-band center theory links adsorbate binding strength to the energy of the metal’s d electrons, while the occupancy of e_g orbitals in octahedrally coordinated transition metals provides a remarkably simple rule of thumb. Shao-Horn and colleagues showed that perovskite oxides perform best when e_g filling is near unity, with the perovskite Ba0.5Sr0.8Co0.2Fe0.2O3−δ sitting at the volcano apex. The oxygen p-band center itself has emerged as a descriptor that captures both activity and the instability that sometimes accompanies it. Perhaps the most striking demonstration of descriptor-guided design came from Sargent’s group, which gelled iron, cobalt, and tungsten into an atomically homogeneous oxyhydroxide. Iron binds oxygen too strongly, cobalt and tungsten too weakly, but interpolation among the three achieved near-optimal binding, delivering a record-low overpotential of 191 millivolts at 10 milliamperes per square centimeter and 500 hours of stable operation.

One of the field’s most consequential realizations is that many catalysts are not what they appear to be. Sulfides, selenides, nitrides, and phosphides that show impressive alkaline OER activity are frequently oxidized in situ under the high anodic potentials of operation, transforming into metal (oxy)hydroxides that are the true active phases. The as-synthesized materials are, in effect, precatalysts. Operando and in situ characterization techniques have confirmed that most transition metal cations undergo surface reconstruction during the OER, typically involving rising oxidation states and the leaching of specific cations or anions. Rather than fighting this transformation, researchers have learned to choreograph it. Nickel substitution in zinc cobaltate spinels pushes the oxygen p-band above the metal d-band, triggering reconstruction into an active oxyhydroxide surface and a sevenfold activity boost that surpasses the iridium oxide benchmark. Iron substitution in otherwise inert cobalt aluminate initiates reconstruction that then self-terminates, preserving the underlying structure.

Crystallinity matters too. Amorphous materials, with their abundant defects and open structures, reconstruct far more readily than their crystalline counterparts. An amorphous NiFeMo oxide prepared by fast co-precipitation rebuilt itself into an oxygen-vacancy-rich oxyhydroxide layer within moments of the reaction starting, requiring only 280 millivolts of overpotential, while the crystalline version needed 358 millivolts because molybdenum ions diffuse sluggishly through the ordered lattice. Deliberate leaching has become a design strategy in its own right. Activating an inactive cobalt chromite spinel at high potential oxidizes chromium from the 4+ to the 6+ state, driving it out of the lattice and leaving behind defects and vacancies that let cobalt reconstruct into active oxyhydroxide, an activity gain of more than an order of magnitude. In another approach, molybdenum sulfide nanosheets coated with nickel-iron layered double hydroxide served as sacrificial templates; five cycles of voltammetry stripped the molybdenum into the growing oxyhydroxide, yielding a catalyst that needed just 242 millivolts at 10 milliamperes per square centimeter.

The review’s survey of recent multi-metal catalysts reveals how these principles converge in practice. Tensile lattice strain engineered into NiFe2O4 spinel ferrites flattened the electronic bands near the Fermi level and tuned e_g occupancy at iron sites, cutting the overpotential to 180 millivolts. Co-doping ruthenium and zinc into Co3O4 selectively activated lattice oxygen while preventing over-oxidation of ruthenium, achieving 172 millivolts and 100 hours of stability at a punishing 500 milliamperes per square centimeter. Vanadium leaching from Co2Fe0.25V0.75O4 left behind a stable vanadium oxide underlayer that compensated charge and prevented cobalt dissolution, sustaining 600 hours at 500 milliamperes per square centimeter. High-valence dopants such as molybdenum, chromium, niobium, and tungsten stabilize low-valence iron and nickel species, and the resulting Fe2+ fraction correlates directly with activity; NiFeMo oxyhydroxide reached 180 millivolts. Anchoring single molybdenum atoms onto NiFe oxyhydroxide nanoarrays strengthened metal–oxygen covalency and activated lattice oxygen, delivering 193 millivolts. Non-oxide systems joined the race as well: cobalt-nickel phosphide nanosheets hit 209 millivolts, vacancy-rich NiFe sulfide reached 213 millivolts and performed at 235 millivolts under quasi-industrial conditions of 6 molar potassium hydroxide at 60 degrees Celsius, and a hierarchical CoMnP/Ni2P array worked as a bifunctional catalyst for both half-reactions, splitting water at just 1.54 volts.

The newest frontier is high-entropy materials, in which five or more elements mix in near-equal proportions to form single-phase solid solutions. The compositional disorder stabilizes the phase, and the so-called cocktail effect of synergistic elemental interactions tunes adsorption energies toward the Sabatier optimum. A high-entropy sulfide of chromium, manganese, iron, cobalt, and nickel outperformed every unary through quaternary sulfide comparison, reaching 100 milliamperes per square centimeter at 295 millivolts, with charge migration from manganese and iron optimizing the cobalt active sites. High-entropy perovskites and spinels followed suit, and in the spinel (CrFeCoNiMo)3O4 the high-valence cobalt and molybdenum shifted the reaction pathway toward the lattice oxygen mechanism, verified by isotope labeling. An amorphous NiFeCoMnAl oxide, dealloyed into a nanoporous architecture, posted 190 millivolts. The authors of the review are candid about what remains: the synergistic interactions among multiple elements are still incompletely understood, stability at industrial current densities is not guaranteed, and bridging from laboratory electrodes to scalable electrolyzer architectures is the decisive next step. But the trajectory is unmistakable. By combining electronic structure engineering, dynamic surface reconstruction, and compositional complexity, researchers are turning the OER from the weakest link in electrochemistry into a solvable design problem, and with it, the prospect of hydrogen made cleanly, cheaply, and at scale moves measurably closer.

Subject of Research: Design strategies and recent advances in 3d transition metal-based multi-metal electrocatalysts for the alkaline oxygen evolution reaction

Article Title: An overview of design strategies and recent advancements in complex 3d transition metal-based electrocatalysts for alkaline oxygen evolution reaction

Article References: Lee, S., Shin, Y., Yeom, K., Shim, J., & Sung, Y.-E. (2025). An overview of design strategies and recent advancements in complex 3d transition metal-based electrocatalysts for alkaline oxygen evolution reaction. Advances in Industrial and Engineering Chemistry, 1(1), Article 2. https://doi.org/10.1007/s44405-025-00001-4

Image Credits: AI Generated

DOI: 10.1007/s44405-025-00001-4

Keywords: oxygen evolution reaction, electrocatalysis, water electrolysis, green hydrogen, transition metal catalysts, surface reconstruction, lattice oxygen mechanism, activity descriptors, high-entropy materials, layered double hydroxides, alkaline media, multi-metal catalysts