Considering the global and growing technological demand for platinum, increasing its utilization is key in the context of green hydrogen production by proton exchange membrane water electrolysis. An effective strategy to increase Platinum utilization in Pt/C hydrogen evolution electrocatalysts is to increase the Pt dispersion on the conductive carbon support and to reduce the Pt nanoparticle size down to Pt clusters or even Pt single sites. In that context utilization of 3D porous N-doped carbon supports is helpful to form and stabilize highly dispersed Pt species and achieve high mass activities. In here we present two approaches for the synthesis of such electrocatalysts with high Pt dispersion for hydrogen evolution: one based on a simple wet impregnation with subsequent thermal reduction, the other based on a vapor phase CVD deposition. We use N-doped mesoporous carbon nanospheres as supports, with high surface area and surface functionality to build Pt nanoparticles, clusters, and single sites. The Pt speciation, depending on the synthesis approach, was thereby investigated a. o. by XRD, XPS, ac-STEM, XAS and electrochemical CO stripping. In all cases, when high Pt dispersion was achieved in form of Pt clusters and single sites, ultra-high mass activity was demonstrated at the RDE level [1,2]. Literature: [1] Zeng, Z.; Küspert, S.; Balaghi, S. E.; Hussein, H. E. M.; Ortlieb, N.; Knäbbeler‐Buß, M.; Hügenell, P.; Pollitt, S.; Hug, N.; Melke, J.; Fischer, A. Small 2023, 2205885. [2] Küspert, S.; Campbell, I. E.; Zeng, Z.; Balaghi, S. E.; Ortlieb, N.; Thomann, R.; Knäbbeler‐Buß, M.; Allen, C. S.; Mohney, S. E.; Fischer, A. Small 2024, 2311260.

Vapor-based deposition techniques are emerging approaches for the design of carbon-supported metal powder electrocatalysts with tailored catalyst entities, sizes, and dispersions. Herein, a pulsed CVD (Pt-pCVD) approach is employed to deposit different Pt entities on mesoporous N-doped carbon (MPNC) nanospheres to design high-performance hydrogen evolution reaction (HER) electrocatalysts. The influence of consecutive precursor pulse number (50-250) and deposition temperature (225-300 degrees C) are investigated. The Pt-pCVD process results in highly dispersed ultrasmall Pt clusters (approximate to 1 nm in size) and Pt single atoms, while under certain conditions few larger Pt nanoparticles are formed. The best MPNC-Pt-pCVD electrocatalyst prepared in this work (250 pulses, 250 degrees C) reveals a Pt HER mass activity of 22.2 +/- 1.2 A mg-1Pt at -50 mV versus the reversible hydrogen electrode (RHE), thereby outperforming a commercially available Pt/C electrocatalyst by 40% as a result of the increased Pt utilization. Remarkably, after optimization of the Pt electrode loading, an ultrahigh Pt mass activity of 56 +/- 2 A mg-1Pt at -50 mV versus RHE is found, which is among the highest Pt mass activities of Pt single atom and cluster-based electrocatalysts reported so far. Mesoporous N-doped carbon nanospheres are used for Pt deposition via a pulsed CVD approach. The process results predominantly in highly dispersed ultrasmall approximate to 1 nm sized Pt clusters along with Pt single atoms. The resulting electrocatalyst reveals an ultrahigh Pt hydrogen evolution reaction mass activity of 56 +/- 2 A mg-1Pt at -50 mV vs. RHE. image

Platinum is one of the best-performing catalysts for the hydrogen evolution reaction (HER). However, high cost and scarcity severely hinder the large-scale application of Pt electrocatalysts. Constructing highly dispersed ultrasmall Platinum entities is thereby a very effective strategy to increase Pt utilization and mass activities, and reduce costs. Herein, highly dispersed Pt entities composed of a mixture of Pt single atoms, clusters, and nanoparticles are synthesized on mesoporous N-doped carbon nanospheres. The presence of Pt single atoms, clusters, and nanoparticles is demonstrated by combining among others aberration-corrected annular dark-field scanning transmission electron microscopy, X-ray absorption spectroscopy, and electrochemical CO stripping. The best catalyst exhibits excellent geometric and Pt HER mass activity, respectively ≈4 and 26 times higher than that of a commercial Pt/C reference and a Pt catalyst supported on nonporous N-doped carbon nanofibers with similar Pt loadings. Noteworthily, after optimization of the geometrical Pt electrode loading, the best catalyst exhibits ultrahigh Pt and catalyst mass activities (56 ± 3 A mg-1 Pt and 11.7 ± 0.6 A mg-1 Cat at -50 mV vs. reversible hydrogen electrode), which are respectively ≈1.5 and 58 times higher than the highest Pt and catalyst mass activities for Pt single-atom and cluster-based catalysts reported so far.

Well-defined nanostructuring over size, shape, spatial configuration, and multi-combination is a feasible concept to reach unique properties of nanostructure arrays, while satisfying such broad and stringent requirements with conventional techniques is challenging. Here, we report designable anodic aluminium oxide templates to address this challenge by achieving well-defined pore features within templates in terms of in-plane and out-of-plane shape, size, spatial configuration, and pore combination. The structural designability of template pores arises from designing of unequal aluminium anodization rates at different anodization voltages, and further relies on a systematic blueprint guiding pore diversification. Starting from the designable templates, we realize a series of nanostructures that inherit equal structural controllability relative to their template counterparts. Proof-of-concept applications based on such nanostructures demonstrate boosted performance. In light of the broad selectivity and high controllability, designable templates will provide a useful platform for well-defined nanostructuring.

Well-defined nanostructuring over size, shape, spatial configuration, and multi-combination is a feasible concept to reach unique properties of nanostructure arrays, while satisfying such broad and stringent requirements with conventional techniques is challenging. Here, we report programmable anodic aluminium oxide templates to address this challenge by achieving well-defined pore features within templates in terms of in-plane and out-of-plane shape, size, spatial configuration, and pore combination. The structural programmability of template pores arises from broad-range anodization voltage adjusting together with uneven aluminium anodization rate designing, and further relies on a systematic blueprint guiding pore diversification. Starting from the programmable templates, we realize a series of nanostructures that inherit equal structural controllability relative to their template counterparts. Proof-of-concept applications based on such nanostructures demonstrate boosted performance. In light of the broad selectivity and high controllability, programmable templates will provide an all-in-one platform for well-defined nanostructuring.

Building nanoparticle (NP) superlattices formed in a complex fashion by subsets that can be explored separately presents a promising approach to realize the next generation of superlattices for different applications. Here, by incorporating self‐aligned and geometrically different subsets of Au NPs into one matrix with the assistance of multi‐pore anodic alumina oxide templates, scaled‐up NP superlattices are constructed with programmable multiple plasmonic resonances. The inter‐peak spectral distance is tailored in a broad wavelength range from less than 50 nm up to about 1000 nm through altering not only the size and height of each subset, but also the number and nature of the NP subset. Importantly, a mechanical oscillator model is developed to elucidate the microscopic origin of the spectral programmability and to reproduce the parameter dependence of the multiple plasmonic resonances. A photoelectrochemical cell using Au NP superlattice embedded photoanodes is investigated as a proof‐of‐concept, demonstrating a high photoresponse improvement of about 260% compared to that of bare film reference. In light of the compatibility of this technique with other plasmonic materials and the geometrical tunability, these findings enable systematic optical controlling toward optical devices with multimodal plasmonics.

Janus heteronanostructures (HNs), as an important class of anisotropic nanomaterials, could facilitate synergistic coupling of diverse functions inherited by their comprised nanocomponents. Nowadays, synthesizing deterministically targeted Janus HNs remains a challenge. Here, a general yet scalable technique is utilized to fabricate an array of programmable Janus HNs based on anodic aluminum oxide binary-pore templates. By designing and employing an overetching process to partially expose four-edges of one set of nanocomponents in a binary-pore template, selective deposition and interfacing of the other set of nanocomponents is successfully achieved along the exposed four-edges to form a densely packed array of Janus HNs on a large scale. In combination with an upgraded two-step anodization, the synthesis provides high degrees of freedom for both nanocomponents of the Janus HNs, including morphologies, compositions, dimensions, and interfacial junctions. Arrays of TiO2-Au and TiO2/Pt NPs-Au Janus HNs are designed, fabricated, and demonstrated about 2.2 times photocurrent density and 4.6 times H2 evolution rate of that obtained from their TiO2 counterparts. The enhancement was mainly determined as a result of localized surface plasmon resonance induced direct hot electron injection and strong plasmon resonance energy transfer near the interfaces of TiO2 nanotubes and Au nanorods. This study may represent a promising step forward to pursue customized Janus HNs, leading to novel physicochemical effects and device applications.

Electrocatalysts for oxygen reduction and/or evolution are key components for proton-exchange membrane fuel cells (PEMFCs) and water electrolysis. However, the slow kinetics of oxygen reduction and/or evolution reactions largely hampers the efficiencies of PEMFCs and water electrolysis. Highly efficient electrocatalysts for oxygen reduction and evolution reactions must meet three requirements: (i) rapid transport of electrons, ions, and products of the reaction; (ii) sufficient catalysts/reactants contact area; and (iii) good intrinsic activity. Nanostructuration of electrocatalysts provides an effective approach to overcome the slow kinetics because nanostructured electrocatalysts with rational design can not only provide sufficient active sites but also promote intrinsic activity of electrocatalysts as well as possess the ability of rapid transport of electrons, ions, and products of the reaction. Especially, electrocatalysts in the form of one-dimensional nanostructures (1D-Nano) such as nanowires (NWs) and nanotubes (NTs) have shown significant advantages, such as high surface area, rapid electron and mass transfer, low vulnerability to dissolution, Ostwald ripening, and aggregation, for oxygen evolution reaction (OER) and oxygen reduction reaction (ORR). In this review, we summarize different strategies for fabricating 1D nanostructure-based electrocatalysts (1D-NanoECs), which are categorized into template-free and template-assisted strategies, and emphasis has been placed on anodic aluminum oxide template–assisted strategies. Then, recent advances of 1D-NanoECs for ORR and OER applications are summarized. Finally, future challenges and opportunities about 1D-NanoECs are discussed.

Nanostructured molybdenum disulfide (MoS2) has been considered as one of the most promising catalysts in the hydrogen evolution reaction (HER), for its approximately intermediate hydrogen binding free energy to noble metals and much lower cost. The catalytically active sites of MoS2 are along the edges, whereas thermodynamically MoS2 favors the presence of a two-dimensional (2-D) basal plane and the catalytically active atoms only constitute a small portion of the material. The lack of catalytically active sites and low catalytic efficiency impede its massive application. To address the issue, we have activated the basal plane of monolayer 2H MoS2 through an ultrathin alumina mask (UTAM)-assisted nanopore arrays patterning, creating a high edge density. The introduced catalytically active sites are identified by Cu electrochemical deposition, and the hydrogen generation properties are assessed in detail. We demonstrate a remarkably improved HER performance as well as the identical catalysis of the artificial edges and the pristine metallic edges of monolayer MoS2. Such a porous monolayer nanostructure can achieve a much higher edge atom ratio than the pristine monolayer MoS2 flakes, which can lead to a much improved catalytic efficiency. This controllable edge engineering can also be extended to the basal plane modifications of other 2-D materials, for improving their edge-related properties.

In this paper, vertically free-standing multiferroic CoFe2O4–Pb(Zr0.52Ti0.48)O3(CFO–PZT) coaxial nanotube arrays with both good ordering and high density were prepared by a template-assisted sol–gel method.

In this work, we demonstrated a bottom-up growth of Ag@SiO2/Ag core-shell nanosphere arrays with tunable SiO2 interior insulator and the optimized surface-enhanced Raman scattering (SERS) substrate based on a nanostructure performed with both high sensitivity and large-area uniformity. Their morphological, structural, and optical properties were characterized, and the induced SERS activities were investigated theoretically by the FDTD simulation and experimentally using analyte molecules. An ultrathin SiO2 shell with tunable thickness can be synthesized pinhole-free by a chemical vapor deposition, working as an interior insulator between the Ag core and Ag out-layer coating. A detection limit as low as 10−12 M and an enhancement factor up to 3 × 107 were obtained, and the SERS signal was highly reproducible with small standard deviation. The method opened up a way to create a new class of SERS activity sensor with high-density ‘hot spots’, and it may play an important role in device design and the corresponding biological and food safety monitoring applications. Copyright © 2016 John Wiley & Sons, Ltd.

Our research work focused on high-density magnetic nanodot arrays using ultra-thin anodic aluminum oxide (AAO) membrane as template. We fabricated the ordered nanomagnetic arrays by high-vacuum thermal evaporation with help from the AAO membrane bonded onto desired substrates. The typical sizes of the nanomagnetic materials were highly controlled at 20 nm and 80 nm ranges by adopting different pore-sizes of AAO. The packing-density was achieved to as high as 6 x 16x10(10) cm(-2), while the morphology was investigated by scanning electron microscope (SEM) and atomic force microscopy (AFM), which confirmed the size-controlled growth and uniformity of size distribution. The nanomagnetic characteristics were investigated by magnetic force microscopy (MFM) and Physical Property Measurement System (PPMS) in which the size-related nanomagnetic effect was confirmed.

The ordering degree of nanostructures is the key to determining the uniformity of surface-enhanced Raman scattering (SERS). However, fabrication of large-area ordered nanostructures remains a challenge, especially with the ultrahigh-density (>1010 cm−2). Here, we report a fabrication of large-area ultrahigh-density ordered Ag@Al2O3/Ag core–shell nanosphere (NS) arrays with tunable nanostructures. The ultrahigh-density (2.8 × 1010 cm−2) ordered NS arrays over a large-area capability (diameter >4.0 cm) enable the uniform SERS signals with the relative standard deviation of less than 5%. The as-fabricated highly reproducible SERS substrate can be applied to detect trace phenolic pollutants in water. This work does not only provide a new route for synthesizing the ultrahigh-density ordered nanostructures, but also create a new class of SERS substrates with high sensitivity and excellent reproducibility.

Cupric pollution is a global problem, and the development of stable and sensitive fluorescent probes for cupric ions in the water phase has long been sought. In the present study, we report on the fabrication of core-shell nanoparticle-based fluorescent chemosensors for Cu2+ detection in aqueous media. The core-shell nanoparticle sensor was prepared by a facile one-pot miniemulsion polymerization, in which the fluorescent dye (4-methamino-9-allyl-1,8-naphthalimide, MANI) was covalently incorporated into particle core and the Cu2+ ligand i.e. Vinylbenzylcyclam (VBC), chemically linked onto the surface. The cyclam-functionalized fluorescent polymeric nanoparticles exhibit a high affinity for Cu2+ ions in aqueous media. Upon the addition of Cu2+, the fluorescent emission of the MANI dye in nanoparticles can be quenched on the basis of intraparticle fluorescence resonance energy transfer (FRET) from the dye in the hydrophobic PMMA core to the Cu2+-cyclam complexes on the nanoparticle surface, and the nanoparticle sensor can selectively detect the Cu2+ in water with the detection limit of 500 nM. The observed FRET efficiencies (31.6-73.4%), as well as the distance (r) between MANI (donor) and Cu2+-cyclam complexes (acceptor), were also determined. No interference was observed from other metal ions, making it a highly sensitive and selective Cu2+ probe. Moreover, the nanoparticle-based fluorescent sensor was applicable in a relatively wide pH range (pH 4-10) in water and it exhibited excellent longterm photostability for Cu2+ detection (>45 days) in aqueous media; thus, this approach may provide a new strategy for ratiometric detection of analytes in environmental and biological applications.