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Single‐atom catalysts (SACs) supported on inorganic materials have attracted much attention in numerous research fields for their high catalytic performance. However, such SACs have been limited by the low metal loading, especially on different types of inorganic supports. Herein, a general approach is presented for preparing SACs on metallic, metal oxide, and perovskite nanosheet (NS) supports to reach a high metal loading of up to 3.94 wt%, by utilizing N‐doped graphene as a sacrificial template that spatially confines the single atoms (SAs). Specifically, the target support material precursors are adsorbed onto the SAs‐stabilized sacrificial template, followed by subsequent heat treatment to transfer the SAs to the support material and to remove the graphene layer. Pt SAs on oxide support exhibits little to no aggregation throughout >10 000 min of annealing at 275 °C, demonstrating high thermal stability, as also supported by ex situ post‐anneal electron microscopy and X‐ray absorption fine structure studies. As a proof‐of‐concept, Pt SACs on SnO2 NSs exhibit high catalytic activity toward chemiresistive sensing of acetone gas (response = 95.4 at 10 ppm, 7.6‐fold enhancement compared with pristine SnO2 NSs) and unprecedented stability under highly humid conditions (27.4% response deterioration at 95% relative humidity). [ABSTRACT FROM AUTHOR]

Multi-heterogeneous oxide sensing layers, i.e., NiO/Fe2O3 catalyst loaded SnO2 fiber-in-tube nanostructures (NiO/Fe2O3–FITs), were rationally synthesized from an electrospinning solution containing a bio-inspired chitosan–bimetal complex template. The NiO/Fe2O3–FITs showed remarkably enhanced sensing properties and superior cross-sensitivity toward sub-ppm levels of formaldehyde. [ABSTRACT FROM AUTHOR]

The development of efficient bifunctional catalysts for the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) is a key issue pertaining high performance Li-O2 batteries. Here, we propose a heterogeneous electrocatalyst consisting of LaMnO3 nanofibers (NFs) functionalized with RuO2 nanoparticles (NPs) and non-oxidized graphene nanoflakes (GNFs). The Li-O2 cell employing the tailored catalysts delivers an excellent electrochemical performance, affording significantly reduced discharge/charge voltage gaps (1.0 V at 400 mA g−1), and superior cyclability for over 320 cycles. The outstanding performance arises from (1) the networked LaMnO3 NFs providing ORR/OER sites without severe aggregation, (2) the synergistic coupling of RuO2 NPs for further improving the OER activity and the electrical conductivity on the surface of the LaMnO3 NFs, and (3) the use of GNFs providing a fast electronic pathway as well as improved ORR kinetics. [ABSTRACT FROM AUTHOR]

Abstract: Lithium–oxygen (Li–O2) batteries are considered as the most promising candidates owing to their higher theoretical energy density than other energy storage devices. However, the unfavorable structure of the air cathode has become a major cause of low performance for Li–O2 batteries, limiting their use in practical applications. To deal with this issue, the rational construction of porous air electrodes, where crucial reactions take place, is in high demand. Among the various dimensional materials, 1D nanomaterials have been frequently applied for air electrodes in several different forms, owing to their fascinating morphologies and unique characteristics. We present a focus review on the recent research relating to 1D nanomaterials adopted as air electrodes in Li–O2 cells. This paper gives the current issues surrounding Li–O2 cells, which are analyzed in terms of the efforts to apply the advantages of 1D nanomaterial electrodes for enhancing the electrochemical performance of the given cells. [ABSTRACT FROM AUTHOR]

Conductive porous materials having a high surface reactivity offer great promise for a broad range of applications. However, a general and scalable synthesis of such materials remains challenging. In this work, the facile synthesis of catalytic metal nanoparticles (NPs) embedded in 2D metal–organic frameworks (MOFs) is reported as highly active and conductive porous materials. After the assembly of 2D conductive MOFs (C‐MOFs), i.e., Cu3(hexahydroxytriphenylene)2 [Cu3(HHTP)2], Pd or Pt NPs are functionalized within the cavities of C‐MOFs by infiltration of metal ions and subsequent reduction. The unique structure of Cu3(HHTP)2 with a cavity size of 2 nm confines the bulk growth of metal NPs, resulting in ultra‐small (≈2 nm) and well‐dispersed metal NPs loaded in 2D C‐MOFs. The Pd or Pt NPs‐loaded Cu3(HHTP)2 exhibits remarkably improved NO2 sensing performance at room temperature due to the high reactivity of catalytic metal NPs and the high porosity of C‐MOFs. The catalytic effect of Pd and Pt NPs on NO2 sensing of Cu3(HHTP)2, in terms of reaction rate kinetics and activation energy, is demonstrated. [ABSTRACT FROM AUTHOR]

The Cover picture shows an electric car powered by a Li–O2 battery driven on a road. The road is covered with graphene, which implies that the Li–O2 battery is supported by an air cathode catalyst composed of oxide nanofibers/nanoparticles attached onto graphene. The small yellow balls are RuO2 nanoparticles whereas the black wires are LaMnO3 nanofibers acting as efficient catalysts for discharging/charging battery. The big yellow balls represent lithium ions, red balls are oxygen molecules, and the gray rocks on the nanofibers are solid reaction products (Li2O2). More details can be found in the Full Paper by Yoon et al. on page 2080 in Issue 16, 2016 (DOI: 10.1002/cssc.201600341). [ABSTRACT FROM AUTHOR]

Single-crystal nanocrystals of catalytic metals and oxides are essential for understanding chemical interactions on well-defined catalyst surfaces. However, a comprehensive understanding of the crystallographic origins for such enhancement has been lacking. This work provides formal evidence of the structure–property relationship through a model study on single-crystal TiO 2. Our approach involves transient pulse heating to manipulate porosity and phase in epitaxially-grown TiO 2 nanosheets along the (0 0 1) plane. Furthermore, we could introduce high-entropy alloy nanoparticles into the system, which exhibited excellent catalytic activity toward CO oxidation, achieving T 90 at 143 °C. This improved performance is attributed to the interplay between the catalytic nanoparticles and the multiphase support, facilitating CO and O 2 adsorption. Our study contributes to a fundamental understanding of structure–property relationships in heterogeneous catalyst systems. Overall, our thermal shock synthesis approach shows much promise for developing single crystal-based advanced nanocatalysts with broad practical implications. [ABSTRACT FROM AUTHOR]

Porous and hollow nanostructures functionalized with nanoscopic catalysts have attracted considerable interest in a wide range of applications depending on surface reactions. In this study, we present an efficient and versatile synthetic strategy of porous metal oxide hollow frameworks (HFs) decorated with noble metal nanoparticles (NPs). The key lies in the use of porous and bicontinuous polystyrene- block -poly(4-vinylpyridine) (PS- b -P4VP) microparticles as templates, which feature pores on the order of several hundred nanometers in size. Homogeneous Pt loading on the surface of the porous microparticles is achieved through the preferential adsorption of Pt precursors onto the P4VP block via electrostatic interactions. Subsequent SnO 2 thin film deposition and calcination ultimately yield honeycomb-like SnO 2 HFs with macropores and uniform distribution of Pt NPs. The Pt NP-loaded SnO 2 HFs exhibit exceptional formaldehyde (HCHO) sensing capabilities, characterized by remarkable sensitivity (31.4 at 5 ppm), rapid response time (4.7 s at 5 ppm), ultra-low detection limit of 10 ppb, and remarkable cross-selectivity. These outstanding features result from their high surface area, gas permeability within porous hollow structures, and well-dispersed Pt NPs, which catalytically activate the sensor. Our study provides great promise for advancing surface catalytic reactions due to their exceptional surface area and gas permeability, paving the way for future applications. [Display omitted] • We present an innovative synthetic strategy for the fabrication of Pt/SnO 2 hollow frameworks. • The key is the use of Pt-functionalized porous block copolymer microparticles as a sacrificial template. • The Pt/SnO 2 HFs demonstrate remarkable sensitivity (31.4 at 5 ppm), rapid response time (4.7 s at 5 ppm). • Our nanoscopic catalyst-loaded porous metal oxide hollow frameworks serve as a versatile catalytic platform. [ABSTRACT FROM AUTHOR]

Electrospun WO 3 nanofibers (NFs) with hierarchically interconnected porosity (HP_WO 3 NFs) are designed by using dual sacrificial templates including zero-dimensional (0D) polystyrene (PS) colloids and one-dimensional (1D) multi-walled carbon nanotubes (MWCNTs). Multi-dimensionally interconnected pore-loaded structures offer much enhanced surface area and abundant gas penetration pathway into the inner sensing layers, which are essential requirements for effective gas adsorption-desorption reactions, fast gas diffusion, and high gas response. Moreover, such porous WO 3 NFs are homogeneously decorated by Pt nanoparticles (Apo-Pt) encapsulated in a protein nanocage, i.e., apoferritin, which enables uniform catalyst sensitization in interior and exterior of highly gas accessible NFs. The HP_WO 3 NFs sensitized by Apo-Pt (Apo-Pt@HP_WO 3 NFs) exhibited highly selective and sensitive acetone response (R air /R gas  = 10.80 ± 0.06 @ 1 ppm) under high humidity atmosphere (90% RH). To investigate the potential suitability as exhaled breath analyzers, we tested three sensor arrays consisting of mesoporous WO 3 NFs templated by MWCNTs (MP_WO 3 NFs), HP_WO 3 NFs, and Apo-Pt@HP_WO 3 NFs. The result revealed that targeted acetone molecules were clearly classified against six different interfering molecules (H 2 S, C 7 H 8 , C 2 H 5 OH, CO, NH 3 and CH 4 ) through principle component analysis (PCA), confirming excellent acetone selectivity of the designed sensor arrays. [ABSTRACT FROM AUTHOR]

Functionalization of catalytic nanoparticles (NPs) on semiconductor metal oxide (SMO) sensing layer is an indispensable process to obtain improved sensitivity and selectivity for high performance chemical sensors. It is a critical challenge to achieve homogeneous distribution of nanoscale catalysts on SMO in consideration that gas sensing characteristics of SMO-based sensing layer are significantly influenced by the size and distribution of catalysts. Here, we propose a highly effective functionalization method to achieve well-distributed catalytic NPs onto one dimensional (1D) SMO nanofibers (NFs) using protein cage templates: apoferrtin. By simply replacing precursor in the apoferritin assisted method, not only precious catalyst such as Pt but also non-precious catalysts such as La and Cu were successfully synthesized in nanoscale ( i.e. , 3–5 nm). Furthermore, the apoferritin-encapsulated catalysts exhibited high dispersion property due to repulsive force between protein shells. For this reason, catalytic NPs were homogeneously decorated on ZnO NFs after electrospinning followed by calcination. Catalytic Pt NPs and Cu NPs functionalized ZnO NFs exhibited approximately 6.38-fold (R air /R gas = 13.07) and 2.95-fold (R air /R gas = 6.04) improved acetone response compared with the response (R air /R gas = 2.05) of pristine ZnO NFs. In the case of La NPs functionalized ZnO NFs, 9.31-fold improved nitrogen monoxide response (R air /R gas = 10.06) was achieved compared with the response of pristine ZnO NFs. The four catalyst-ZnO composite NFs successfully distinguished simulated breath components such as acetone, toluene, nitrogen monoxide, carbon monoxide, and ammonia with well-classified patterns by principal component analysis (PCA). This work demonstrated a robustness of synthetic and functionalization method using bio-inspired protein templates combined with electrospinning technique and a promising potential of using non-precious catalysts to establish diverse sensing material libraries that can be applicable to breath pattern recognition for diagnosis of diseases. [ABSTRACT FROM AUTHOR]

The lack of bifunctional features of perovskite oxide toward the oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) significantly limits its use as a cathode catalyst for rechargeable Zn–air batteries (ZABs). Thus far, numerous techniques to disperse additional catalysts on a perovskite host have been suggested to overcome this problem; however, cost-effectiveness and catalyst lifespan remain unsatisfactory. Herein, we present cobalt-based-nanoparticle-decorated Sr 0.95 Nb 0.1 Co 0.7 Fe 0.2 O 3–δ (S0.95NCF) by a simple ex-solution method and use it as a novel air-electrode catalyst. We successfully implemented the socketed nanoparticles with various compositions at different reduction temperatures, achieving notably enhanced activity towards OER and ORR. More importantly, the newly designed catalyst exhibits record-high charge/discharge durability over 500 h (or 1500 consequent cycles) when used as the ZABs cathode. Our findings provide essential guidelines for designing heterostructured electrocatalysts for future energy devices, in which multifunctionality is desirable. [Display omitted] • Ex-solution is applied to Sr 0.95 Nb 0.1 Co 0.7 Fe 0.2 O 3 –δ at various reduction temperatures. • The exsolved metals are elaborately explored depending on ex-solution conditions. • CoFe-nanoalloy ex-solution enhances electrochemical performances for OER and ORR. • The designed catalyst exhibits record-high durability for the Zinc-air batteries. [ABSTRACT FROM AUTHOR]