Nanomaterials Research (United States)

Increasing environmental pollution and shortage of critical resources call for technologies capable of achieving total resource recovery from waste materials. In this study, high leaching rates of 99.16% for lithium and 97.37% for iron were obtained from spent lithium iron phosphate (LFP) batteries through electrochemical (EC) advanced oxidation processes (EAOPs), and associated leaching mechanism was subsequently investigated. Moreover, residual C, Fe, and P elements in leach residue were directly converted into a P, N-doped asymmetric single-atom Fe catalyst (Fe-CN3P), enabled by well-dispersion of Fe elements and removal of surface passivation layers during leaching. When activated with peroxymonosulfate (PMS), Fe-CN3P catalyst exhibited a pseudo-first-order kinetic rate of 10.768 min-1 for bisphenol A (BPA) degradation, which is approximately 2-10 times higher than those of conventional single-atom catalysts. Based upon experimental and theoretical investigation, the presence of P in the local coordination environment was found to substantially enhance catalytic activity of Fe sites. P incorporation alters the adsorption mode of HSO5 - on Fe active centres and increases Bader charges in the FeIV═O reactive intermediate, thereby improving the capability of Fe to withdraw electrons from the BPA molecules. This study offers new perspectives for synergistically advancing "comprehensive resources recovery" and "waste to treat waste."

Abstract In the study of complex systems, the intricate interdependence among individual components leads to emergent properties that cannot be solely attributed to the properties of the components themselves. This principle is central to compositionally complex materials (CCMs), where interactions between different elements introduced into the structure result in unprecedented material properties. The emergence of high entropy materials (HEMs) in 2004 further increase complexity by achieving high configurational entropy (Sconfig) leading to unique properties and stabilizing phases that would otherwise undergo demixing due to positive reaction enthalpy. HEMs and CCMs represent an emerging family of materials where multiple principal elements occupy equivalent crystallographic sites. This atomic architecture gives rise to extraordinary properties such as tailorable electronic structures, lattice distortion effects, and synergistic interactions, resulting from their vast, near-infinite combinatorial space. Although the field is still in its infancy, early discoveries highlight their disruptive potential, particularly in energy technologies where robustness and durability are critical. Their exceptional thermal stability, corrosion resistance, and electro-chemo-mechanical durability position HEMs and CCMs as game-changers for applications demanding resilience under harsh operating conditions, such as batteries, fuel cells, and hydrogen storage systems. Beyond performance advantages, CCMs challenge traditional materials discovery frameworks. Their extensive design space makes conventional trial-and-error approaches impractical, creating an ideal platform for deploying AI-driven high-throughput computational screening, multiscale modeling, and autonomous experimental workflows. This convergence of complexity and innovation offers unprecedented opportunities to accelerate the identification of next-generation energy materials. This roadmap compiles insights from leading experts in the field of CCMs across key energy domains, including electrochemical storage, catalysis, thermoelectrics, and turbomachinery. Their contributions critically assess the current state of this material family highlighting unresolved scientific challenges, technological barriers, and the key advancements needed to move beyond the current state-of-the-art. Special emphasis is placed on combinatorial synthesis and high-throughput approaches and their potential to trigger exponential development of this emerging family of materials. Focused on energy applications, this roadmap provides a comprehensive overview of a time-critical topic, emphasizing the need for material innovation and joint efforts from academia and industry.

Hydrogel brushes comprise cross-linked polymer chains that are attached at one end to a substrate. Their network architecture promotes electrochemical stability, which renders these materials suitable for electrochemical applications. However, the electrochemical properties of such hydrogel brushes have not yet been studied yet. In this work, we investigate the role of the cross-linker in the electrochemical behavior of negatively charged poly(3-sulfopropyl methacrylate) (PSPMA) hydrogel brushes. Using electrochemical impedance spectroscopy, we study the role of layer resistance in a poor solvent (0.1 M KOH) and the role of charge transfer in a good solvent (0.1 M KCl). In 0.1 M KOH, we observe that the polymer layer limits the ion diffusion to the electrode and that this phenomenon depends on the cross-linker content. There is an optimum in cross-linker content, for which the ion diffusion experiences the least resistance. We attribute this optimum to a variance in the flexible and rigid polymer phase. In 0.1 M KCl, we find that the solvated brush thickness is the parameter that determines the extent of the charge transfer resistance. The more cross-linked a hydrogel brush is, the lower the swelling ratio in a good solvent and thus the lower the charge transfer resistance becomes. With this knowledge, we can use the cross-linker content as a tool to minimize the layer resistance or tune the charge transfer resistance, which is useful for corrosion protection, electrochemical sensing, and ion gating applications.

Piezocatalytic hydrogen evolution enables the conversion of mechanical energy into chemical fuels, but its efficiency is constrained by a trade-off between piezoelectric polarization and electronic conductivity. Strong piezoelectric polarization is essential for sufficient driving force, yet highly polar materials typically suffer from poor conductivity, which limits bulk-to-surface charge transport. Conversely, enhancing conductivity often compromises piezoelectric performance, resulting in a bottleneck in piezocatalysis. Herein, we decouple piezoelectricity and conductivity using atomically dispersed nickel single atoms on amino-functionalized UiO-66 (Ni SAs@UiO-66-NH2). Introducing polar amino groups and asymmetric Ni─N coordination significantly enhances the piezoelectric response, increasing the piezoelectric coefficient d33 from 48 to 242 pm V-1. Simultaneously, hydrogen adsorption at Ni sites under mechanical stress triggers a pressure-induced semiconductor-to-metal transition, creating transient metallic conduction pathways that facilitate efficient electron extraction without sacrificing bulk polarization. As a result, hydrogen adsorption sites shift from framework carbons to Ni centers, yielding near-optimal H* adsorption energetics (ΔGH * approximately 0.12 eV at 100 MPa), and enabling rapid polarization-driven hydrogen evolution. Consequently, the Ni SAs@UiO-66-NH2 catalyst achieves exceptional hydrogen evolution rate of 1871 µmol g-1 h-1 in deionized water and 17613 µmol g-1 h-1 in methanol-containing media, surpassing reported MOF-based piezocatalysts and competing with leading photo-piezocatalytic and photocatalytic systems.

Engineering bifunctional electrocatalysts featuring promoted adsorption for multiple intermediates and reactants via interface modulation strategies is critical for urea-assisted water splitting toward sustainable energy conversion. However, exploring efficient bifunctional electrocatalysts capable of driving both the hydrogen evolution reaction (HER) and urea oxidation reaction (UOR) at high current densities remains challenging. Herein, a self-supported bifunctional electrode is constructed on nickel foam, where the cooperative CoNi LDH is decorated with low-content Pt nanospheres (Pt-CoNi LDH/NF) for urea-assisted H 2 production. The strong metal-support interaction (SMSI) and multi-metal synergy collectively regulate the adsorption/desorption behavior of key reaction species, thereby lowering the energy barrier for the rate-determining step and improving overall catalytic efficiency. The optimized catalyst exhibits substantially reduced potentials of 1.32 V (UOR) and -30 mV (HER) to reach 10 mA cm -2 . A urea-assisted electrolytic cell merely requires 1.36 V to afford 10 mA cm -2 . Notably, in a practical anion-exchange membrane (AEM) electrolyzer configuration, the Pt-CoNi LDH/NF electrode maintains stable at 2 A cm -2 , while preserving high UOR/HER bifunctional activity. This study develops an integrated approach that couples urea-containing wastewater remediation with energy-efficient hydrogen production. The Pt-CoNi LDH/NF nanospheres catalyst fabricated via a corrosion-drop-anchoring approach shows superior activity and stability toward HER, UOR, and urea-assisted OWS. • The superhydrophilic/aerophobic nanostructure and interface engineering boost reaction kinetics. • Pt sites optimize H* adsorption for HER and Ni 2+ /Ni 3+ cycle for UOR, enabling bifunctional activity. • The assembled electrolyzer requires only 1.73 V to reach 1 A cm -2 .

Supraparticles (SPs) are assemblies of smaller particles, and they form an interesting material class. One way through which these structures can be formed is self-assembly (SA) in spherical confinement, and what makes them unique is that they combine the properties of the smaller particles with collective properties arising from the length scale on which these smaller particles are ordered. Additionally, the limited number of particles in an SP enables them to form structures that are not found in bulk systems. An example of this is icosahedral symmetry, which is the equilibrium structure for SPs up to several hundreds of thousands of particles. Although these icosahedral structures have been investigated through computer simulations and several experimental techniques have been used to analyze them in 3D, the number of experimental datasets published is so limited that no statistically relevant conclusions have been drawn so far. The experimental technique most commonly applied to study them is scanning electron microscopy (SEM), but with this, only quantitative information about the surface of the SPs can be obtained. By using a combination of 3D confocal and stimulated emission depletion (STED) microscopy on extremely well-index-matched (within 0.002) fluorescent core-shell, colloidal silica spheres (of 442-478 nm in diameter with polydispersities below 1%), we obtained full 3D real-space datasets of tens of SPs within several hours. The structures were classified based on bond order parameters and deviations from local centrosymmetry, using an unsupervised machine learning model. From this, we are able to correctly classify structures that are commonly misidentified using SEM. Additionally, the quantitative real-space analysis gave experimental insights into the SA pathway and defect formation mechanisms of mostly icosahedral SPs.

The pursuit of metallic materials approaching their theoretical strength has long been hindered by interface instability at the nanoscale. A recent study by Li et al., writing in Science , reveals that introducing coherent interfaces with negative excess energy in Ni–Mo alloys enables sustained strengthening down to sub-nanometer scales. These energetically favorable interfaces achieve near-theoretical strength (∼5 GPa), marking a new paradigm in atomic-scale interface engineering for ultrahigh-performance metals.

In response to growing demands for environmentally friendly flame-retardant materials, this study develops a novel waterborne polyurethane (WPU) by incorporating the reactive phosphaphenanthrene-based compound DOPO-HQ into the polymer backbone. The modified WPUs, denoted as P-WPUx, exhibit significantly enhanced flame retardancy without appreciably compromising mechanical performance. With only 3 wt % DOPO-HQ loading, P-WPU3 achieves an LOI of 35.35%, satisfies the UL-94 V-0 requirement, and retains mechanical robustness with 33.0 MPa tensile strength and 737.8% elongation. Comprehensive analyses confirm that DOPO-HQ operates via a dual-phase mechanism: scavenging free radicals within the gas phase while simultaneously facilitating carbonaceous layer development in the condensed phase. These findings underscore the potential of molecularly integrated phosphorus-containing modifiers in the design of high-performance, sustainable flame-retardant WPU materials.

Defects are ubiquitous in halide perovskites and play a critical role in determining their structural stability and optoelectronic performance. Achieving atomic-scale identification and understanding of these defects in perovskite is essential for the rational design of high-performance optoelectronic devices. Using an aberration-corrected scanning transmission electron microscope, we directly visualize the atomic structure of the PbCs antisite defect in CsPbBr3 perovskite. The PbCs antisite was found to shorten the Pb─Pb bond length by approximately 20 pm, inducing a local polarization phenomenon and ∼3% compressive strain around the defect. Based on the identified atomic-scale configuration, first-principles calculations revealed that the PbCs antisite induces a semiconductor-to-metal transition, driven by additional electron donation from the substituted Pb atoms that shift the Fermi level into the conduction band. These findings establish a fundamental understanding among atomic-scale structure, polarization, and electronic structure modulation in antisite defects, providing valuable insights for defect engineering strategies toward stable and efficient perovskite optoelectronic devices.