Research

The oxygen evolution reaction (OER) is hindered by sluggish kinetics due to its complex four-electron, proton-coupled mechanism. While noble metal oxides like IrO2 and RuO2 are effective OER catalysts, their high cost and unsatisfactory stability limit large-scale applications. High-entropy layered double hydroxides (HE-LDHs) offer a promising alternative by enabling multi-metallic site tuning and entropy-driven phase stabilization. Herein, VCoNiCuZn and MoCoNiCuZn HE-LDHs respectively modulated by high-valence V4+/V5+ and Mo6+ are hydrothermally synthesized on Ni foam. The MoCoNiCuZn HE-LDH achieved an overpotential of 186 mV at 10 mA cm−2, which is significantly lower than that of 306 mV obtained from CoNiCuZn LDH. The strong M-O covalency induced by high-valence metals facilitates charge redistribution and d-p orbital overlap, activating lattice oxygen and promoting the lattice oxygen mechanism (LOM). The resulting OER performance surpasses most reported multi-principal element materials and rivals noble-metal-doped LDHs. Moreover, high-entropy stabilization presents excellent structural durability and long-term electrochemical stability, highlighting the promise of noble-metal-free HE-LDHs for water splitting.  Xiahua Zhong, et al.  Adv. Funct. Mater. 2025, 35 (47), 2518240. (Frontispiece)

Airborne microbes such as bacteria, viruses, or fungi are a major cause of respiratory ailments, including allergies and pathogenic infections. Despite advances in modern healthcare and public health measures, preventing the transmission of airborne microbes is still very challenging. The microbes may stay alive for a while after landing on a face mask, giving them the chance to infect another individual. A holistic approach is to disinfect the microbes on face mask before inhaling into the upper respiratory tract with functionalized green materials. Fast-growing balsa wood (BW) sheets were first converted into flexible membrane, followed by in situ growth of Cu-based metal–organic framework (Cu-MOF) into pores. The membrane maintains great flexibility, as demonstrated through mechanical folding and twisting. The agar diffusion test was used to qualitatively assess the efficacy of a flexible membrane coupled with MOF particles in antimicrobial application against Gram-positive and Gram-negative bacteria causing respiratory illness. The inhibition zones with a radius of ∼2 mm were observed against Klebsiella pneumoniae and Pseudomonas aeruginosa, while a larger inhibition zone with a radius of ∼4 mm was recorded against Staphylococcus aureus, indicating great potential in inhibiting the production of all strains of microbes. Such green functional materials would find a broad bio application to benefit human health. Manish Neupane, et al. ACS Appl. Bio Mater. 2025, 8 (12), 11125-11133. (Supplementary Cover) 

Carbon nanotubes (CNTs) and their allotropes have been regarded as promising materials for electric double-layer supercapacitors (EDLCs). It is well accepted that the higher surface area of carbon will enable a higher capacity of energy storage. An interesting question is what could happen if the half channel size is less than the Stern layer spacing. In this study, we grew CNTs into carbonized basswood for EDLCs, in which the CNT density varied in bass carbon sheets with different thicknesses, eventually giving various pore/channel sizes. Electrochemical analyses revealed that the bass carbon with a higher CNT density exhibits inferior performance compared to specimens with lower CNT densities. Further investigation through electrochemical impedance spectroscopy suggests that such anomalous behavior in energy storage is attributed to the restricted ion diffusion within the densely packed CNTs in bass carbon channels. Manish Neupane, et al. Appl. Phys. Lett. 2025, 126 (23), 233904.

Lignin is a waste product in the paper industry and lignocellulosic biorefineries, in addition to being the second most abundant renewable biopolymer on Earth. Valorization of useless lignin into high value-added advanced materials not only helps address the environmentally detrimental biowaste but also satisfies the societal need for energy. While lignin has been converted into porous carbon, made into slurry, and pasted onto metal forms as an electrode for lithium-ion batteries and supercapacitors, there remains issues with how to scale up the process while achieving great area and mass capacitances in the fabricated lignin-carbon electrodes. In this work, a thick freestanding electrode coupled by lignin carbon and sodium without any binder and additives was fabricated demonstrating a specific area capacitance of 19.7 F cm−2 at a current density of 1 mA cm−2, which is the highest among to date reported freestanding lignin carbon electrodes with similar thickness. This excellent electrochemical performance originates from high electro-positivity and oxygen content promoted by the sodium. This work brings a new strategy towards lignin utilization and energy storage through coupling lignin carbon and alkali metals.  Manish Neupane, et al. Batter. Supercaps. 2023, 2300193. (Cover Feature) 

For most electrodes fabricated with carbon, transition metal compounds, or conductive polymers, the capacitance may deteriorate with cyclic charging and discharging. Thus, an electrochemically stable supercapacitor has long been pursued by researchers. In this work, the hierarchical structure of balsa wood is preserved in the converted carbon which is used as a supporting framework to fabricate electrodes for supercapacitors. Well-grown carbon nanotubes (CNTs) on interior and exterior surfaces of balsa carbon channels provide two advantages including 1) offering more specific surface area to boost capacitance via electric double layer capacitance and 2) offering more active Fe and Ni sites to participate in the redox reaction to enhance capacitance of the balsa carbon/CNTs electrode. The balsa carbon/CNTs demonstrate an excellent area capacitance of 1940 mF cm−2. As active sites on Ni and Fe catalysts and inner walls of CNTs are gradually released, the capacitance increases 66% after 4000 charge–discharge cycles. This work brings forward a strategy for the rational design of high-performance biomass carbon coupled with advanced nanostructures for energy storage. Qing He, et al. Small, 2022, 2200272.

Fresh and clean water is highly demanded throughout the world. To effectively address the need, nanomaterials enabled nanotechnology has been explored as a means of more efficient, reliable, and environmentally friendly approach towards water treatment practices. In this work, the earth abundant and sustainable wood, e.g., basswood, was selected and carbonized into porous carbon as host skeleton, and metal-organic frameworks (MOFs), e.g., MOF-199 with extremely high surface area, were grown throughout all channels in the porous basswood carbon. Targeting the traditional organic pollutant, methyl orange (MO), the combination of MOFs and basswood carbon (MOFs@carbon) demonstrates a remarkable adsorption capacity, which is 243% and 454% higher than basswood carbon and MOF-199, respectively. Such an outstanding adsorption performance originates from that the positively charged carbon pulls MO molecules close to carbon surface, leading to a high MO molecule concentration, and then the concentration gradient drives the MO molecules to be stored inside MOFs, functioning like pockets. These findings highlight the potential application of coupled MOFs and biomass carbon in addressing water remediation. Akhter Zia, et al. Nano Res. 2024, 17 (6), 5661-5669.

Developing efficient sorbent systems with a high CO2 adsorption capacity and ease of regeneration is crucial for carbon capture. This work presents a bioinspired approach using three-dimensional (3D) porous carbon derived from abundant Balsa wood. CO2 on these materials has been systematically investigated using kinetic characterization, in situ Fourier-transformed infrared (FTIR) spectroscopy, and theoretical calculations. The 3D carbon materials possess a high surface area and abundant hydroxyl (OH) groups, which act as basic sites to interact with acidic CO2, significantly enhancing the CO2 adsorption capacity. Specifically, KOH-treated Balsa carbon could achieve a CO2 adsorption capacity of 4.1 mmol g–1 at 600 mbar, outperforming other carbon-based adsorbents. Density functional theory calculations supported the experimental findings, showing favorable chemisorption with an adsorption energy of −0.64 eV for an OH-functionalized model carbon surface. This study highlights the importance of surface functionalization in enhancing the CO2 adsorption capacity and provides insights for designing advanced carbon-based sorbents. Yuqing, Meng, Manish Neupane, et al. ACS Sustain. Chem. Eng. 2025, 13 (16), 5974-5984.

Promoters play a critical role in tuning the activity and selectivity of Fe catalysts in CO2 hydrogenation to produce light olefins, which are key building blocks in the petrochemical industry. Herein, by a combined experimental and theoretical approach, we show that high and stable performance of Fe catalysts could be achieved by taking advantage of the promotional effect of both Zn and Zr. Structural characterization indicates that ZnO could improve the dispersion and reducibility of Fe oxides and facilitate the formation of active Fe carbide species, whereas ZrO2 could stabilize the structure and catalytic performance, especially the selectivity of hydrocarbon products. In situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) experiments suggest that carbonate, bicarbonate, formate, and methoxy are essential intermediates in the CO2 hydrogenation to hydrocarbon products, including paraffins and olefins. The conversion kinetics of each intermediate species are dependent on the type of promoters as well as the phase structure of the active Fe species. DFT calculations revealed a strong correlation between the formation energy of surface oxygen vacancies and that of Fe carbide species in promoted Fe oxides, in accordance with experimental results. Min Wang, et al. ACS Catalysis. 2025, 15 (8), 5954-5967.

In the current energy and environment scenario, it is imperative to develop energy efficient routes for chemical manufacturing that also pave the way for mitigation of greenhouse gas emissions. This work presents an efficient pathway for continuous syngas production via a chemical looping conversion of the two most potent greenhouse gases-CH4, and CO2. The well-known dry-reforming process of converting CH4, and CO2 to syngas is energy-intensive and suffers from catalyst deactivation. The chemical looping approach, on the other hand, provides avenues for mitigating catalyst deactivation and enabling improved energy efficiency. The key to such process enhancements lies in the intricate structure–function relationships of the catalyst and its correlation to the process variables. We present the reduction and oxidation characteristics of 5 wt.% Ni/Ce1−xZrxO2-based catalysts (x = 0, 0.4, and 0.625). We demonstrate low temperature CH4 activation over Ni-promoted samples as opposed to pure Ce1−xZrxO2. Moreover, our results depict an optimum regeneration of these catalysts when oxidized by CO2, and H2O, which allows for chemical looping operation of steam reforming of methane as well. Process variables were tuned to optimize the CH4 conversion (over 80%), and H2/CO ratio at 650 °C. The impact of this work lies in showcasing the opportunities to design chemical looping reactors for energy efficient syngas production from waste greenhouse gases. Yuan Tian, Zoe Benedict, et al. Top. Catal. 2023, 66, 1581-1593.

The energy-efficient conversion of methane (CH4) to syngas represents a transformative pathway for advancing the global hydrocarbon economy. While conventional reforming processes are well established for producing syngas, a key intermediate for high-value fuels and chemicals, chemical looping reforming of methane offers a compelling alternative. By decoupling the reduction and oxidation steps, chemical looping approaches inherently minimize side reactions and enhance product selectivity. This review explores the critical material and economic considerations necessary for the development of robust, energy-efficient chemical looping technologies for dry reforming of methane. Metal oxide-supported catalysts, incorporating noble or transition metals, are the primary catalysts for chemical looping applications. Catalyst performance is governed not only by the intrinsic reactivity of active metals toward CH4 and CO2 activation but also by the redox behavior of oxide supports and the interfacial dynamics at the metal–support boundary. Key strategies for improving methane conversion efficiency and ensuring long-term catalyst durability include lowering C–H bond activation barriers, enhancing the oxygen storage capacity of supports, and engineering metal–support interactions to suppress coking and sintering. Zoe Benedict, et al. Mater. Today Sustain. 2025, 31, 101128.

Protonic ceramic electrochemical cells (PCECs) have the potential in reducing the energy input and carbon emissions in ethylene production from ethane dehydrogenation. The performance of conventional perovskite-based anode materials for ethane conversion in PCECs is limited by their low active surface area and proneness to coke deposition. In this work, for the first time, we demonstrate the use of aligned carbon nanotube forests (CNTFs) as a novel anode material for an ethane fueled PCEC to co-produce ethylene and electricity. The CNTF electrode was grown on the electrolyte by the chemical vapor deposition (CVD) method. Highly dispersed iron carbide nanoparticles are formed in situ on the CNTFs during the CVD process, acting as highly active catalysts for ethane dehydrogenation. The novel PCECs show superior catalytic and electrochemical performances to that using conventional perovskite-based anodes. The cell also exhibits excellent durability and anti-coking abilities within 100 h test. This work showcases the promising application of nanostructured carbon, a new class of non-perovskite materials, as the multifunctional electrode materials for PCECs. Min Wang, et al. Carbon, 2022, 199, 379-386. 

Van der Waals (vdW) materials consisting of two-dimensional (2D) building blocks have strong in-plane covalent bonding and weak interlayer interactions. While monolayer 2D materials exhibit impressive fracture resistance, as demonstrated in hexagonal boron nitride (h-BN), preserving these remarkable properties in vdW materials remains a challenge. Here we reveal an anomalous mechanical interlayer coupling that involves interlayer-friction toughening and edge-reconstruction embrittlement during the fracture of multilayer h-BN. Both asynchronous and synchronous fracture modes and their flaw-size dependence are identified. Edge reconstruction in the synchronous fracture mode can eliminate a toughening mechanism induced by lattice asymmetry in monolayer h-BN, leading to embrittlement of the multilayer h-BN, while the asynchronous fracture mode results in greater fracture resistance. Such findings will provide fundamental guidelines for engineering interlayer interactions in vdW materials including heterostructures and layered architectures for better mechanical and functional performances. Zhigong Song, Yingchao Yang, et al.  Nat. Mater. 2025, 24, 1554-1560. 

If a bulk material can withstand a high load without any irreversible damage (such as plastic deformation), it is usually brittle and can fail catastrophically. This trade-off between strength and fracture toughness also extends into two-dimensional materials space. For example, graphene has ultrahigh intrinsic strength (about 130 GPa) and elastic modulus (approximately 1.0 TPa) but is brittle, with low fracture toughness (about 4 MPa*m1/2 ). Hexagonal boron nitride (h-BN) is a dielectric two-dimensional material with high strength (about 100 GPa) and elastic modulus (approximately 0.8 TPa), which are similar to those of graphene. Its fracture behaviour has long been assumed to be similarly brittle, subject to Griffith’s law. Contrary to expectation, we report high fracture toughness of single-crystal monolayer h-BN, with an effective energy release rate up to one order of magnitude higher than both its Griffith energy release rate and that reported for graphene. We observe stable crack propagation in monolayer h-BN, and obtain the corresponding crack resistance curve. Crack deflection and branching occur repeatedly owing to asymmetric edge elastic properties at the crack tip and edge swapping during crack propagation, which intrinsically toughens the material and enables stable crack propagation. Our in situ experimental observations, supported by theoretical analysis, suggest added practical benefits and potential new technological opportunities for monolayer h-BN, such as adding mechanical protection to two-dimensional devices. Yingchao Yang, et al. Nature, 2021, 594, 57-61. 

Perfect graphene is believed to be one of the strongest materials, yet its resistance to fracture is much less impressive. The modest fracture toughness is thought to be related to the general brittle nature in the fracture process of graphene and its two-dimensional (2D) analogous. The brittleness also makes it extremely difficult to assess mechanical properties of 2D materials. The introduction of carbon nanotubes (CNTs) into bulk materials has proven to be a widely accepted method for toughening and strengthening materials. To date, such toughening effect of CNTs on 2D materials is largely unknown. A unique material, rebar graphene, has been synthesized that consists of CNTs embedded in graphene. In this study, by implementing a “dry” transfer technique, the freely suspended rebar graphene was systematically tested under uniaxial tension mode inside a scanning electron microscope. Our combined experiments and molecular dynamics simulations confirm that the embedded CNTs divert and bridge the propagating crack and provide a toughening mechanism for the material. Our work identifies a promising extrinsic toughening strategy for 2D materials and provides mechanistic insights into the fracture process of graphene hybrid material. Emily Hacopian, Yingchao Yang, et al. ACS Nano, 2018, 12 (8), 7901-7910. 

We have developed an in situ nanomechanical testing platform for quantitative measurement of the mechanical proprieties of 2D materials inside SEM. In contrast to the local, transverse probing by AFM, our device enables a uniform in-plane loading of the freestanding 2D sample. Our testing is facilitated by a new technique of dry transfer of the ultrathin 2D sample to the loading device. We perform in situ tensile tests of monolayer and bilayer MoSe2, and observed the brittle fracture processes of crack initiation, propagation, and final failure in real time. The measured elastic modulus and fracture strength of MoSe2 are 177.2 ± 9.3 and 4.8 ± 2.9 GPa, respectively. The large variation of fracture strengths is attributed to the pre-existing flaws caused by CVD growth. Based on the Griffith theory of fracture, we estimate the fracture-producing crack size as 33.0 ± 30.9 nm. Finally, we discuss implications of our results on the statistical strength as well as the fragility of brittle 2D materials. Yingchao Yang, et al. Adv. Mater. 2017, 29 (2), 1604201. 

The strong force that originates from breaking covalent bonds can be easily quantified through various testing platforms, while weak interfacial sliding resistance (ISR), originating from hydrogen bonding or van der Waals (vdW) forces, is very challenging to measure. Facilitated by an in-house nanomechanical testing system, we are able to precisely quantify and clearly distinguish the interfacial interactions between individual carbon fibers and several substrates governed by either hydrogen bonding or vdW forces. The specific ISR of the interface dominated by vdW forces is 3.55 ± 0.50 μN mm−1 and it surprisingly increases to 157.86 ± 44.18 μN mm−1 if the interface is bridged by hydrogen bonding. The ad hoc studies demonstrate that hydrogen bonding rather than vdW forces has great potential in sewing the interface if both surfaces are supportive of the formation of hydrogen bonds. The findings will enlighten the engineering of interfacial interactions and further mediate the entire mechanical performance of structures. Zhenxing Cao, et al. RSC Adv. 2020, 10, 17438-17443.

Carbon nanotubes (CNTs) can improve the fracture toughness of ceramic composites. It is widely believed that defects in the CNTs will alter key properties that ultimately dictate composite toughening. However, to date there have been no studies that directly correlate these specific properties to controlled defect levels in CNTs. This type of investigation is presented here, using ceramic nanocomposites with a polymer derived ceramic (PDC) matrix, reinforced with multiwalled CNTs. This work includes basic fracture measurements on full composite films, combined with careful testing of individual CNTs embedded in the same PDC matrix. The defect levels in these CNTs were controlled with high energy carbon ions. By using this approach, it was possible to directly correlate defect levels with the interfacial shear strength (IFSS) of the CNT/PDC interface, the CNT fracture strengths, and the pull-out lengths observed after fracture of the full composites. The radiation induced defects led to substantial increases in the IFSS, and only a marginal decrease is observed in the measured fracture strength. Based on this, the shorter pull-out lengths that occurred with higher defect levels were primarily attributed to stronger bonding at the CNT/PDC interface. Yingchao Yang, et al. Carbon, 2017, 115, 402-408. 

Carbon nanotubes (CNTs) have been considered an ideal reinforcement for light-weight and high-strength ceramic matrix composites. Understanding the interfacial properties between CNTs and the matrix is crucial for engineering the desired properties in such composites. Here in-situ pull-out experiments with a polymer derived ceramic (PDC) matrix are carried out with both pristine CNTs and CNTs coated with Al2O3 (CNT/Al2O3) produced by Atomic Layer Deposition (ALD), using micro-fabricated devices in a scanning electron microscope. This carefully designed comparative study makes it possible to better understand the interfacial interactions between CNTs and PDC matrices. The interfacial shear strength (IFSS) of CNT-PDC is 9.99 ± 2.84 MPa, while the IFSS of (CNT/Al2O3)/PDC with ∼3 nm Al2O3 coating thickness is 14.52 ± 2.66 MPa, demonstrating a 45.3% improvement. The non-linear failure observed with the coated CNTs is also indicative of energy dissipation mechanisms that promote toughening in ceramic matrix composites. The improved properties in (CNT/Al2O3)/PDC are believed to originate from increased surface roughness, which leads to mechanical interlocking at the interface during the pull-out process. The combination of special interlayer structures such as ALD Al2O3 and strong CNTs opens up interesting opportunities for improving the mechanical properties of ceramic nanocomposites reinforced by CNTs. Yingchao Yang, et al. Carbon, 2015, 95, 964-971. 

Hierarchically organized three-dimensional (3D) carbon nanotubes/graphene (CNTs/graphene) hybrid nanostructures hold great promises in composite and battery applications. Understanding the junction strength between CNTs and graphene is crucial for utilizing such special nanostructures. Here, in situ pulling an individual CNT bundle out of graphene is carried out for the first time using a nanomechanical tester developed in-house, and the measured junction strength of CNTs/graphene is 2.23 ± 0.56 GPa. The post transmission electron microscopy (TEM) analysis of remained graphene after peeling off CNT forest confirms that the failure during pull-out test occurs at the CNT–graphene junction. Such a carefully designed study makes it possible to better understand the interfacial interactions between CNTs and graphene in the 3D CNTs/graphene nanostructures. The coupled experimental and computational effort suggests that the junction between the CNTs and the graphene layer is likely to be chemically bonded, or at least consisting of a mixture of chemical bonding and van der Waals interactions. Yingchao Yang, et al. Nanoscale, 2017, 9, 2916-2924. 

In this study, well-aligned single-walled carbon nanotube (SWCNT) films were utilized as lamellae to prepare a multifunctional nanocomposite by a feasible ‘layer-by-layer’ preparation method. This structural design can not only dramatically reduce the agglomeration effect of SWCNTs, but also achieve high in-plane stiffness. It was found that the well-aligned SWCNT films contribute to the high stress-transfer between CNTs and present good wettability with epoxy matrix, thereby improving the mechanical enhancement. Interestingly, this laminated structure possesses distinct electrical behaviors under different loading conditions. The electrical resistance linearly increases with the increase of in-plane tensile strain but is insensitive to bending. This work could provide in-depth understanding on the mechanical and electrical properties of CNT-based laminated nanocomposites. Chao Sui, Yingchao Yang, et al. Carbon, 2018, 139, 680-687.