Hollow Porous Structure Research Articles

Superior triethylamine-sensing properties based on SnO2 hollow nanospheres synthesized via one-step process

Due to serious harm of triethylamine (TEA) to environmental safety and human health, it is significant to synthesize gas-sensitive materials with high performance for TEA detection. However, it is still a challenge to achieve high-sensitivity detection of TEA at low temperature for a sensor synthesized through an economical and efficient method. In this work, hollow-structured SnO2 (HS-SnO2) nanospheres have been fabricated by a facile, low-cost hydrothermal method in one step, which exhibit superior TEA-sensing properties, including not only ultrahigh response (127.75) for 100 ​ppm TEA, good selectivity, but also fast response and recovery time (17/28 ​s), low detection threshold (1 ​ppm) and robust stability at a relatively low optimum operational temperature of 225 ​°C. The excellent gas-sensitizing performances are ascribed to porous hollow structures with rich oxygen vacancies that provide abundant active sites for raising O2 adsorption and reaction of TEA and oxygen species. This work offers an effective and economical strategy for fabricating high-performance TEA sensors for industrial applications.

In-situ immobilization strategy for single-atom iron sites to enhance oxygen reduction reaction in Zn–air batteries and microbial fuel cells

A straightforward and environmentally friendly approach was utilized to synthesize single-atomic Fe–N–C catalyst. In-situ immobilization of Fe3+ during the formation of polydopamine (PDA) and ZIF-8 in aqueous solution effectively prevent metal agglomeration. The mutual promotion of PDA and aqueous solution constructed the hybrid-level porous hollow structure in P–FeNC. This method extends the solution scope from organic solution system to water solution, thus providing fascinating opportunities for investigating metal-N-C catalyst by in-situ mixing various metal salt precursor and dopamine. The optimal P–FeNC catalyst demonstrates superlative oxygen reduction reaction (ORR) performance, with the half-wave potentials (E1/2) of 0.886 V, 0.79 V, and 0.72 V in 0.1 M KOH, 0.5 M H2SO4, and 0.05 M PBS solutions, which exceeded commercial 20 wt% Pt/C. The combinatorial impacts of highly dense FeN4 active sites and interconnected hierarchical mesopores/macropores are presumed to underpin the observed enhancement in ORR performance. Further evaluations show that the power densities of P–FeNC equipped zinc-air battery (ZAB) and microbial fuel cell (MFC) are 460 mW/cm2 and 3083 ± 10 mW/m2, respectively. This study confirms the feasibility to design the innovative single-atom catalyst in aqueous solution and provides constructive ideas to employ the high-performance P–FeNC electrocatalyst in ZABs and MFCs.

Porous hollow nanospheres nickel phosphide and its high catalytic hydrogenation performance on naomaohu coal soluble portion and model compounds

The catalytic conversion of oxygen-containing aromatic ring in lignite under mild conditions is crucial to obtain clean liquid fuel. Here, hollow nanosphere Ni3P-500–24 catalysts were prepared at a calcination temperature of 500 °C and acid-etching time of 24 h. The porous hollow nanospheres structure could expose more catalytic sites, and the electron-rich nickel exhibited a good catalytic activity. The conversion rate of benzyl phenyl ether (BPE) was 100 % (140 ℃, 1 MPa H2, 2 h), and the main products were methylcyclohexane and cyclohexanol, indicating that the catalyst had good catalytic hydrocracking performance. In addition, the catalyst exhibited certain deoxygenation activity and high product selectivity for other oxygen-containing model compounds. For the catalytic hydrogenation of Naomaohu coal (NMHC) soluble portion, the content of alkanes increased from 19 % to 47 %, while the content of oxygen-containing compounds decreased from 56 % to 21 %, which further demonstrate that the catalyst have good catalytic hydrogenation and deoxygenation performance. Density Functional Theory (DFT) calculations showed that the properties of the Ni3P-500–24 catalyst was similar to noble metal, which could activate H2 to produce two kind of active hydrogen: H radical and diatomic hydrogen. The synergistic pathways for the transfer of active hydrogen during the catalytic hydroconversion (CHC) process were analyzed. Above results could provide theoretical guidance for the conversion of lignite into high-quality clean liquid fuels.

2D/1D nested hollow porous ZnIn2S4/g-C3N4 heterojunction based on morphology modulation for photocatalytic CO2 reduction

The two-dimensional (2D) composite one-dimensional (1D) heterojunction structure is one of the main strategies for constructing composite photocatalysts for photocatalytic reduction of carbon dioxide (CO2). However, morphology modulation for 2D/1D heterojunction is an important way to enhance performance. In this study, a unique 2D/1D ZnIn2S4/g-C3N4 nested hollow porous heterojunction structure was constructed by an in-situ growth method with spatial confinement effect. The synergy between 1D g-C3N4 and 2D ZnIn2S4, achieved through advanced morphology modulation at an optimal ratio of 3:1, results in the formation of the CZ-3 photocatalyst. This unique configuration enables a simultaneous high yield of carbon monoxide (CO) and methane (CH4), achieving 79.96 μmol/g and 17.33 μmol/g respectively, under visible light irradiation without the need for sacrificial agents. The core of this enhanced photocatalytic performance is attributed to the employment of a type-II heterojunction mechanism, which optimizes the transfer of photogenerated carriers. Ultraviolet-visible diffuse reflection spectrum, photoluminescence spectrum and photoelectrochemical analysis reveal the effect of morphology on photocatalytic performance in terms of visible light absorption, photogenerated carrier pairs separation and electronic band structure of heterojunction. By combining the advantages of 2D/1D structural benefits with the efficient charge dynamics of a type-II heterojunction, this work provides new ideas for improving the morphology of composite heterojunction photocatalysts with 2D/1D structure to enhance the photocatalytic CO2 reduction performance.

SO2-resistant hollow carbon spheres encapsulated Pt nanoparticles for benzene oxidation

In the catalytic combustion of volatile organic compounds (VOCs) using noble metal catalysts, resistance to SO2 poisoning poses a significant challenge. To tackle this problem, Pt nanoparticle catalysts encapsulated in hollow carbon spheres (Pt@HCS catalysts) are synthesized. The Pt@HCS catalyst exhibits excellent benzene conversion, achieving 100 % conversion at 165 °C under an air velocity of 20,000 mL/(g h). Compared to the conventional supported Pt/HCS catalyst, the Pt@HCS catalyst demonstrates a significantly improved resistance to SO2 poisoning. In the presence of 25 ppm SO2, the Pt@HCS catalyst is capable of maintaining a 100 % benzene conversion rate within 24 h, whereas the conversion rate of Pt/HCS drops substantially to approximately 52 %. It is confirmed that the hollow porous structure provided a larger specific surface area and more adsorption sites, thereby facilitating benzene oxidation. More importantly, in situ DRIFTS reveals that the adsorption and desorption processes of SO2, along with the generation of substances like SO32−, are strictly limited to the surface of the carbon shell, thereby preserving the integrity of the internal reaction environment. Multiple characterizations combined with density functional theory (DFT) have demonstrated a unique separation effect over Pt@HCS, whereby the hydroxyl groups on the carbon shell preferentially capture SO2 while allowing benzene molecules to enter the cavities of the catalyst. In this way, any internal ingress of SO2 and competition with benzene for Pt adsorption is effectively avoided. This study offers a potential solution to enhance the performance of noble metal catalysts in the presence of sulfur compounds.

Rational design of hollow bimetallic sulfide@carbon with abundant heterogeneous interfaces and conductive network synergies for efficient microwave absorption

Developing composites with rational structural design and multicomponent synergistic effects is regarded as a promising strategy for achieving excellent impedance matching and high intensity attenuation performance. Herein, a hierarchical and multifunctional hollow porous Co3S4@NiCo2S4@BPC composite with integrated strong microwave absorption (MA) and self-cleaning properties was designed. The resultant composite exhibits remarkable EMW absorption behavior with a minimum reflection loss (RLmin) of −68.1 dB at 2.3 mm. The multicomponent synergy achieves a satisfactory heterogeneous structure, invoking intense interfacial polarization. Additionally, the residual functional groups and lattice defects induced by S doping further enhance the microwave attenuation. Meanwhile, the hierarchical hollow porous structure facilitates the impedance matching between the absorber and air. Notably, the composite has ideal radar cross-section (RCS) reduction and excellent hydrophobicity, demonstrating its outstanding MA properties as well as the potential applications in complex environment. Therefore, this work provides a novel strategy for the rational design of high-performance absorbers.

In Situ Flash Synthesis of Ultra-High-Performance Metal Oxide Anode through Shunting Current-Based Electrothermal Shock.

The synthesis of anode materials plays an important role in determining the production efficiency, cost, and performance of lithium-ion batteries (LIBs). However, a low-cost, high-speed, scalable manufacturing process of the anode with the desired structural feature for practical technology adoption remains elusive. In this study, we propose a novel method called in situ flash shunt-electrothermal shock (SETS) which is controllable, fast, and energy-saving for synthesizing metal oxide-based materials. By using the example of direct electrothermal decomposition of ZIF-67 precursor loaded onto copper foil support, we achieve rapid (0.1-0.3 s) pyrolysis and generate porous hollow cubic structure material consisting of carbon-coated ultrasmall (10-15 nm) subcrystalline CoO/Co nanoparticles with controllable morphology. It was shown that CoO/Co@N-C exhibits prominent electrochemical performance with a high reversible capacity up to 1503.7 mA h g-1 after 150 cycles at 0.2 A g-1and stable capacities up to 434.1 mA h g-1 after 400 cycles at a high current density of 6 A g-1. This fabrication technique integrates the synthesis of active materials and the formation of electrode sheets into one process, thus simplifying the preparation of electrodes. Due to the simplicity and scalability of this process, it can be envisaged to apply it to the synthesis of metal oxide-based materials and to achieve large-scale production in a nanomanufacturing process.

Hollow Porous Structures for Improving the Sensitivity of Colorimetric Array Gas Sensors

AbstractDetecting volatile organic compounds (VOCs) in exhaled breath is a promising research area for disease diagnosis. Mass transfer behavior plays a crucial role in determining the detection performance of VOCs. However, the high mobility of exhaled breath poses a substantial challenge for the mass transfer process. Here, the distinct mass transfer behavior of mobile gaseous molecules is discovered by employing the schlieren imaging technique to visualize gas flow. The results demonstrate that hollow porous structures exhibit a higher gas flow flux than solid film and microporous structures, thereby generating a sufficient probability of contact reactions for mobile gaseous molecules. The proposed colorimetric array sensors offer enhanced sensitivity and stability for detecting mobile gaseous molecules. The discovery will serve as a foundational milestone is anticipated in elucidating the behavior of gas mass transfer and promoting its potential application in disease detection through the analysis of human exhaled breath.

Dual Redox Mediators Assisted Hierarchically Porous Hollow Carbon Shell Cathode for Enhanced Performance Li‐O2 Battery

AbstractRechargeable lithium‐oxygen (Li‐O2) batteries with high theoretical energy density are regarded as a promising candidate for the booming electric vehicle manufacturing industry, whereas their commercial application is hindered due to poor cyclic stability caused by the sluggish kinetics and inevitable cathode passivation. Herein, a synergistic working mechanism of Li‐O2 battery is initiated by implementing well‐designed hollow carbon shells with hierarchically porous hollow structure (HCS) assisted by dual redox mediators (RMs) simultaneously, so as to systemically address issues of diminished discharge capacity and reaction kinetics. The hierarchically porous structure of HCS constructs more space to accommodate Li2O2, increases the accessibility of active sites, and enhances discharge capacity. More importantly, the dual RMs regulate the growth mechanism of Li2O2 in surface‐mediated mode, resulting in an easily decomposed film‐like Li2O2 with higher electron transport capacity and improving the reaction kinetics. As a result of the synergistic effort, an HCS‐based Li‐O2 battery with dual RMs manifests a total discharge capacity of 24580 mA h g−1 and a prolonged cycle life of 2500 h at the current density of 100 mA g−1. This design philosophy will open up a new way to optimize and upgrade the cathode materials of Li‐O2 batteries.

RGO doped MOFs derived α-Fe2O3 nanomaterials for self-supporting ppb-level NO2 gas sensor

Metal-organic frameworks (MOFs) derived metal oxide semiconductors (MOSs) with hierarchical and hollow porous structures can reduce detection limits and improve response of gas sensor. Hence, we synthesized reduced graphene oxide (rGO) doped nano-octahedral α-Fe2O3 nanomaterials on Indium-Tin Oxide (ITO) conductive glass as self-supporting NO2 gas sensors by using the solvothermal and calcination methods with MIL-88 as sacrificial templates. Compared to pure α-Fe2O3, the response of rGO/α-Fe2O3-3 sensor improved by more than 8 times and the theoretical detection limit 101 ppb. The improvement in gas response can be attributed to the formation of p-n heterostructure between rGO and α-Fe2O3, as well as the rGO providing more active sites for gas adsorption and special nano-octahedral α-Fe2O3. Consequently, this research provides insights for advancing self-supporting high-performance NO2 sensors based on MOFs derived MOSs.

Manganese doped hollow cobalt oxide catalysts for highly efficient oxygen evolution in wide pH range

Heteroatomic substitution of spinel oxides can theoretically optimize oxygen evolution reaction (OER) via redistribution of charges and modification of d-band center. However, the wide pH range of electrocatalysis and catalytic mechanism are still great challenges. Herein, we successfully construct heteroatom Mn-substituted spinel Co3O4 (Mn-Co3O4) with porous hollow sphere structure for highly efficient and wide pH range OER. Benefiting from the atomic Mn-substitution and charge transfer, the Co site in Mn-Co3O4 displays an increased ratio of Co3+/Co2+. Electrochemical measurements demonstrate that Mn-Co3O4 exhibited superior OER activities with small overpotentials of only 305, 520 and 460 mV to afford a current density of 10 mA cm−2 in alkaline, neutral and acidic media, respectively. Meanwhile, Mn-Co3O4 also possesses favorable long-term stability in wide-pH electrolyte. The improved reaction kinetics of Mn-Co3O4 are mainly attributed to the unique hollow sphere structure with high specific surface area, and the increased high valency of Co, which can introduce the d-band center modification of Mn-Co3O4, and reduce the adsorption energy of oxygen intermediates in rate-determining step (RDS).

Efficient CO2 photoreduction enabled by the one-dimensional (1D) porous structured NiTiO3 nanorods

In this study, porous, and hollow nanorods of NiTiO3 (NiTiO3 NRs-p: 2–3 μm in length and 400 nm in diameter) are successfully prepared using an ethylene glycol-mediated approach at room temperature (25 °C), followed by calcination at 700 °C in air environment. Their rough surfaces and accumulated holes are advantageous for adsorption and subsequent photoreduction of carbon dioxide (CO2) under UV–vis irradiation. The NiTiO3 NRs-p exhibit superior performance in terms of photoconversion of CO2 (purity 99.999 %, 100 mL/min) into gaseous CO (57.833 μmolg−1 h−1) and CH4 (24.33 μmolg−1 h−1) with an overall CO2 selectivity (SCO2) of 89 %. In contrast, the solid NiTiO3 nanorods (NiTiO3 NRs) exhibit moderate performance in CO2 reduction, producing CO (30.33 μmolg−1 h−1) and CH4 (11.50 μmolg−1 h−1) with a CO2 selectivity of SCO2 = 60 %. NiTiO3 NRs-p exhibits superior photocatalytic activity against CO2 over other NiTiO3 morphologies with similar physical and chemical properties (such as nanoparticles (NPs) and nanofibers (NFs). This enhancement in photocatalytic activity can be attributed to the porous texture and hollow rod-like structure of NiTiO3 NRs-p, which provides a larger number of active sites to promote rapid mass transport. This unique one-dimensional (1D) structure also facilitates the separation of photogenerated electron-hole pairs, as demonstrated experimentally. This study opens a new room for a simple and facile routes for the photocatalytic conversion of CO2 into solar fuels.

Coupling metal organic frameworks nanozyme with carbon nanotubes on the gradient porous hollow fiber membrane for nonenzymatic electrochemical H2O2 detection

In this paper, we present a gradient porous hollow fiber structure integrated the signal transduction within a microspace, serving as a platform for cellular metabolism monitoring. We developed a nonenzymatic electrochemical electrode by coupling carbon nanotubes (CNT) and metal organic frameworks (MOF) nanozyme on three-dimensional (3D) gradient porous hollow fiber membrane (GPF) for in-situ detection of cell released hydrogen peroxide (H2O2). The GPF was used as a substrate for cell culture as well as the supporting matrix of the working electrode. The ultrasonically coupled CNT@MOF composite was immobilized on the outer surface of the GPF by means of pressure filtration. Notably, the MOF, acting as a peroxidase mimic, exhibits superior stability compared to traditional horseradish peroxidase. The incorporation of CNT not only provided sufficient specific surface area to improve the uniform distribution of MOF nanozyme, but also formed 3D conductive network. This network efficiently facilitates the electrons transfer during the catalytic process of the MOF, addressing the inherent poor conductivity of MOFs. The GPF-CNT@MOF nonenzymatic bioelectrode demonstrated excellent electrocatalytic performance including rapid response, satisfactory sensing selectivity, and attractive stability, which enabled the development of a robust in-situ cellular metabolic monitoring platform.

Metal-organic-framework-derived boron and nitrogen dual-doped hollow mesoporous carbon for photo-thermal catalytic conversion of CO2

The facile fabrication of hollow materials with rich defects is highly desired for photothermal conversion of CO2. Herein, we successfully prepared Zn, B, and N co-doped hollow mesoporous carbon (BHNC) by directly pyrolyzing phenylboronic acid/melamine/ZIF-8. The hollow porous structure of the resulting BHNC material can not only achieve high photothermal conversion efficiency but also effectively promote substrate mass transfer. Moreover, the introduction of B extends the light absorption scope of the material, offers active sites for chemical adsorption and further activation of CO2, significantly promoting the cycloaddition reaction. Benefiting from their high specific surface area, hollow mesoporous nanoarchitecture and rich defects, the optimized BHNC can be employed as a high-efficiency catalyst for the CO2 cycloaddition reaction under light irradiation and ambient conditions, affording 3 times higher yield of 4-(chloromethyl)-1,3-dioxolan-2-one (97%) than that of ZIF-8-800. This study provides a new strategy for the design of efficient catalysts for CO2 conversion under mild conditions.

Nitrogen-Doped Titanium Dioxide for Selective Photocatalytic Oxidation of Methane to Oxygenates.

Photocatalytic conversion of methane (CH4) to value-added chemicals using H2O as the oxidant under mild conditions is a desired sustainable pathway for synthesizing commodity chemicals. However, controlling product selectivity while maintaining high product yields is greatly challenging. Herein, we develop a highly efficient strategy, based on the precise control of the types of nitrogen dopants, and the design of photocatalysts, to achieve high selectivity and productivity of oxygenates via CH4 photocatalytic conversion. The primary product (methanol) is obtained in a high yield of 159.8 μmol·g-1·h-1 and 47.7% selectivity, and the selectivity of oxygenate compounds reached 92.5%. The unique hollow porous structure and substituted nitrogen sites of nitrogen-doped TiO2 synergistically promote its photo-oxidation performance. Furthermore, in situ attenuated total reflectance Fourier transform infrared spectroscopy provides direct evidence of the key intermediates and their evolution for producing methanol and multicarbon oxygenates. This study provides insights into the mechanism of photocatalytic CH4 conversion.

Constructing three-dimensional architectures to design advanced anodes materials for sodium-ion batteries: from nanoscale to microscale

Sodium-ion batteries (SIBs) are emerging as a possible substitute for lithium-ion batteries (LIBs) in low-cost and large-scale electrochemical energy storage systems owing to the lack of lithium resources. The properties of SIBs are correlated to the electrode materials, while the performance of electrode materials is significantly affected by the morphologies. In recent years, several kinds of anode materials involving carbon-based anodes, titanium-based anodes, conversion anodes, alloy-based anodes, and organic anodes have been systematically researched to develop high-performance SIBs. Nanostructures have huge specific surface areas and short ion diffusion pathways. However, the excessive solid electrolyte interface film and worse thermodynamic stability hinder the application of nanomaterials in SIBs. Thus, the strategies for constructing three-dimensional (3D) architectures have been developed to compensate for the flaws of nanomaterials. This review summarizes recent achievements in 3D architectures, including hollow structures, core-shell structures, yolk-shell structures, porous structures, and self-assembled nano/micro-structures, and discusses the relationship between the 3D architectures and sodium storage properties. Notably, the intention of constructing 3D architectures is to improve materials performance by integrating the benefits of various structures and components. The development of 3D architecture construction strategies will be essential to future SIB applications.

Encapsulation of hydroxycamptothecin within porous and hollow poly(L-lactide-co-ε-caprolactone) microspheres as a floating delivery system for intravesical instillation.

Intravesical instillation is an effective post-treatment for bladder cancer performed by delivering medications directly into the bladder to target the remaining cancer cells. The current study thus aimed to develop porous poly(L-lactide-co-ε-caprolactone) (PLCL) microspheres encapsulated with 10-hydroxycamptothecin (HCPT) via microfluidics to serve as a drug delivery system with persistent floating capacity and sustained HCPT-release property for intravesical instillation. A microfluidic device was designed to fabricate PLCL microspheres and encapsulate HCPT (HCPT-MS) within them; methanol and tridecane were introduced into an oil phase as a co-solvent and pore-forming agent, respectively, to regulate the floating ability of microspheres. The physicochemical properties of the resulting microspheres were characterized, and the floating behavior, release profile and anti-tumor effects of HCPT-MS were investigated. The obtained spherical HCPT-MS were 119.23 μm in size, monodisperse, and featured a porous concave surface and hollow structure. The encapsulation efficiency and drug loading of HCPT within HCPT-MS was around 67% and 4.9%, respectively. HCPT-MS exhibited impressive floating capabilities in water, PBS and artificial urine even in a simulated bladder dynamic environment. These microspheres remained afloat after being subjected to 90 repeated simulated urination processes. The sustained release of HCPT from these floating microspheres lasted for more than 10 days. The IC50 (half maximal inhibitory concentration) of HCPT-MS was calculated to be 52.14 μg mL-1. T24 cells (human bladder cancer cells) when cultured with HCPT-MS at such a concentration were severely inhibited, and the inhibition further enhanced with an increase in culture time. Hence, the feasibility of the current porous and floating HCPT-MS as a formulation for intravesical instillation to deliver medications into the bladder with sustained release and stability was thus substantiated.

Hierarchical hollow porous structures of nickel-doped λ-MnO2 anodes for Li-ion energy storage systems

Ni–MnO2 hollow structures were synthesized and used as anodes for LICs, where they exhibited higher energy and power than the LIBs and SCs.

Regulating hollow structure of CL-20 microspheres using microjet droplet technology to enhance safety and combustion performance

Hollow energetic microspheres have attracted great attention in the field of materials due to their wide application potential. However, scalable, simple, and low-cost production methods have not been achieved yet. In this study, using nitrocellulose (NC) as a binder, hollow and porous hollow CL-20 microspheres were prepared by the assist of microjet droplet technology. The effects of receiving liquid temperature, solution concentration, and solvent type on the morphology, particle size, shell thickness, and pore size of the CL-20 microspheres were systematically investigated. Furthermore, the influences of shell thickness and pore size on the dispersibility, crystal structure, thermal decomposition, mechanical sensitivity, and combustion behavior of CL-20 microspheres were further studied. The results showed that precise control over the shell thickness and pore size of CL-20 microspheres could be achieved by adjusting the process parameters. Compared to raw CL-20, the CL-20 microspheres exhibited excellent dispersibility and improved thermal and safety performance (raw CL-20 vs CL-20 microspheres, 40.3° vs 27.1° ∼ 29.1°; 240.4℃ vs 241.1 ∼ 246.2℃; 2 J vs 25 ∼ 32.5 J). Ignition experiments demonstrated that the hollow and porous hollow structures significantly enhanced the combustion flame of CL-20, shortened the burning time, and thereby improved energy release efficiency. This preparation method is simple and efficient, providing a new approach for the fabrication of multi-structured hollow energetic microspheres.

Structural Effects on ORR Performances of Carbon-Free Connected Platinum–Cobalt Catalysts with Chemically Ordered Superlattice Structures

Polymer electrolyte fuel cells (PEFCs) have been considered as the promising next-generation energy-conversion technology, owing to their high energy efficiency and clean emissions. However, a sluggish oxygen reduction reaction (ORR) rate and the low durability of conventional catalysts in PEFCs limit the wider commercialization. To address these issues, our group has developed a carbon-free, connected Pt1–Fe1 catalyst with a porous hollow capsule structure. This catalyst comprises the nano-sized network formed by the connection of Pt1–Fe1 nanoparticles and exhibits an enhanced ORR specific activity (9 times higher than a commercial Pt/C) as well as excellent durability against start-stop operations due to the carbon-free structure.[1,2] However, during the load cycle operation, iron is dissolved from the catalyst, leading to the loss of ORR activity and the degradation of polymer electrolytes caused by the Fenton reaction.In this work, carbon-free and iron-free connected Ptx-Co1 catalysts with chemically ordered superlattice structures have been developed for the first time, as shown in Fig. 1(a). In addition, the metal compositions and chemically ordered (superlattice) degrees in the catalysts were controlled to investigate the structural effects on ORR activity and durability of the connected Ptx-Co1 catalysts.Herein, we employed the silica-coating method for the catalyst synthesis, which involves the combination of silica coating and high-temperature annealing. As shown in Fig. 1(b), the surface of the Ptx-Co1 nanoparticles/SiO2 sample was coated with thin silica layers to prevent the detachment of Ptx–Co1 nanoparticles from the SiO2 template as well as the large catalyst agglomeration and coalescence during the annealing process. We controlled the chemically ordered degrees of the connected Pt1–Co1 and Pt3–Co1 catalysts by using different annealing temperatures. The XRD patterns of the catalysts showed the peaks corresponding to L10 type and L12 type chemically ordered structures for the connected Pt1–Co1 and Pt3–Co1 catalysts annealed at 600°C, respectively. These two catalysts possessed ordered degrees (S) of ca. 50–60%. The TEM images of the connected Ptx–Co1 catalysts showed the formation of connected Ptx–Co1 nanonetwork and porous hollow capsule structures.The electrochemical measurements of ORR activity and durability were conducted in a 0.1 M HClO4 electrolyte solution. The connected Pt1–Co1 and Pt3–Co1 catalysts achieved 6- and 10-times higher ORR specific activities than that of Pt/C, respectively. Subsequently, the ORR activity and load cycle durability (0.6 V for 3 s Û 1.0 V for 3 s at 60 °C) of the connected Pt3–Co1 catalyst with different ordered degrees (S = 0%, 28%, and 58%) were evaluated. As the ordered degrees in the connected Pt3–Co1 catalysts were higher, the ORR specific activity was increased. Also, the retention of the specific activity of the ordered catalyst (S = 58%) was higher than that of the disordered catalyst (S = 0%) after 10,000 load cycles. The STEM-EDX line mapping results showed that 83% of the alloyed Co retained in the catalyst with a higher ordered degree even after 10000 load cycles, whereas the disordered and lower ordered catalysts retained lower Co ratios after the test, indicating the suppression effect of an ordered structure on metal dissolution. In addition, the L12 ordered Pt3–Co1 structure remained in the connected catalyst (S = 58%) after load cycle test, confirmed by the TEM diffraction analysis.In summary, we successfully developed the connected Ptx-Co1 catalysts with chemically ordered superlattice structures. In addition, we clarified the structural effects of metal composition and ordered degree in connected Ptx-Co1 catalysts on ORR activity and load cycle durability. These results provide useful guidelines for the design of advanced ORR catalysts towards high-performance PEFCs. Acknowledgement The part of this presentation is based on results obtained from a project, JPNP20003, commissioned by the New Energy and Industrial Technology Development Organization (NEDO).