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![a) Typical TEM images of TCNTs‐1/2/3. b,c) Raman spectra of CNTs and TCNTs. d) The HOMO and LUMO plots of PCNT and HCNT with their eigenvalues. e) The most stable structures and the corresponding parameters for O2 adsorption on PCNT and HCNT. f) CV curves of TCNTs and CNTs tested in O2‐saturated 0.1 m NaOH. g) O2 stripping voltammetry curves for TCNTs in 0.1 m NaOH. h) Synthetic route of zigzag‐type CNR@CNT. i,j) TEM image and schematic diagram of GNR@CNT. k) ORR activity of catalysts in 0.5 m H2SO4. l) Polarization and power density curves of catalysts as a function of the areal current density with cathode catalyst loadings in PEMFC. m) Stability of the indicated catalysts in PEMFC measured at 0.5 VRHE. n) Theoretical calculations of free energy diagrams for different carbon atoms. (a–g) Reproduced with permission.[¹³⁴] Copyright 2014, Royal Society of Chemistry. h–n) Reproduced with permission.[¹³⁶] Copyright 2018, Springer Nature.](profile/Sicong-Qiao-2/publication/355935855/figure/fig2/AS:11431281173112283@1688754409675/a-Typical-TEM-images-of-TCNTs-1-2-3-b-c-Raman-spectra-of-CNTs-and-TCNTs-d-The-HOMO.png)
a) Typical TEM images of TCNTs‐1/2/3. b,c) Raman spectra of CNTs and TCNTs. d) The HOMO and LUMO plots of PCNT and HCNT with their eigenvalues. e) The most stable structures and the corresponding parameters for O2 adsorption on PCNT and HCNT. f) CV curves of TCNTs and CNTs tested in O2‐saturated 0.1 m NaOH. g) O2 stripping voltammetry curves for TCNTs in 0.1 m NaOH. h) Synthetic route of zigzag‐type CNR@CNT. i,j) TEM image and schematic diagram of GNR@CNT. k) ORR activity of catalysts in 0.5 m H2SO4. l) Polarization and power density curves of catalysts as a function of the areal current density with cathode catalyst loadings in PEMFC. m) Stability of the indicated catalysts in PEMFC measured at 0.5 VRHE. n) Theoretical calculations of free energy diagrams for different carbon atoms. (a–g) Reproduced with permission.[¹³⁴] Copyright 2014, Royal Society of Chemistry. h–n) Reproduced with permission.[¹³⁶] Copyright 2018, Springer Nature.
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Efficient electrocatalysts are highly desirable for promising electrochemical reactions that are likely to mitigate the long‐standing energy and environment problems mainly resulting from human activities. However, most of them are partly composed by scarce and precious metals, thus hampering their large‐scale utilization. In this regard, developin...
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... Excellent electrical properties, decent mechanical capabilities, and better stability made CNTs based materials as the best substitute for Pt-based expensive materials [41][42][43]. However, when compared to Pt wire, electrocatalytic activity for CNT-based materials is still inferior due to lesser number of active sites [44,45]. To improve their performance in miniature energy devices, CNT-based fibrous materials must have excellent electrocatalytic activity along with sufficient conductivity. ...
One-dimensional wire-shaped dye-sensitized solar cells (DSSCs) are promising flexible energy conversion devices for new generation wearable microelectronics. Typically, Pt-based expensive materials are employed as counter electrodes for device fabrication along with photoanode and electrolyte. In this work, a facile electrodeposition approach has been adopted to deposit bimetallic oxide of cobalt and nickel over the surface of carbon nanotube-based fiber and used it as counter electrodes in fiber-shaped DSSCs. Modified Ti wire (TiO2 nanotubes/N719 dye) was used as a photoanode and NiCoO2 modified CNTs fiber twisted around the photoanode operated as a counter electrode in fibrous DSSCs. Electron transfer behavior of iodide/triiodide (I⁻/I3⁻) redox couple at counter electrode studied via cyclic voltammetry (CV) which revealed that the modified CNTs fiber electrode performs better as compared to Pt wire and pristine CNTs fiber. The lower value of charge transfer resistance was calculated via EIS (electrochemical impedance spectroscopy), which also suggested a facile reduction of triiodide to iodide at the counter electrode. The outcomes realized that the electrodeposited CoNi-oxide nanoparticles over the CNTs fiber significantly improve the device performance because of the harmonious effect of active sites and inner pathways facilitated by the NiCoO2 nanoparticles and CNTs fiber, respectively. This work recommends a facile method for the fabrication of efficient electrodes for flexible and wearable energy harvesting devices.
... Nanotubes have been a popular one-dimensional allotropic form of carbon in the scientific domain. Currently, a wide variety of nanotubes composed of various different elements, such as carbon, titanium, tungsten, zinc, etc., have attracted the attention of scientists [1][2][3][4]. It has been established that a wide range of layered materials can form nanotubes since the discovery of nanotube morphology [5]. ...
The present study demonstrates the thermal stability and photocatalytic activity of TiO2-based nanotubes with respect to post-hydrothermal treatment. Titanate nanotubes were synthesized by adapting an alkali hydrothermal method from TiO2 sol using NaOH as a catalyst. The effect of post-hydrothermal heating on the properties—such as structure, morphology, textural properties, and activity—of as-synthesized one-dimensional titania nanostructure is investigated in detail. The characterizations are carried out using SEM, EDX, TEM, XRD, and a BET surface area analyzer. When heated in the presence of water in an autoclave, the protonated titanate phase of the nanotubes converts to anatase phase. Meanwhile, the tubular morphology is gradually lost as the post-hydrothermal heating duration increases. The photocatalytic activity was assessed utilizing the photo-oxidation of an amaranth dye. It is discerned that the as-prepared nanotubes are photocatalytically inactive but become active after post-hydrothermal processing. The activity trend follows the formation of the active phase—the titanate phase crystallizes into a photocatalytically-active anatase phase during post-hydrothermal heating. The effect of experimental parameters, such as reaction pH, dye concentration, and amount of catalyst, on the dye removal is studied. The findings also highlight that the role of holes/OH• is more prominent as compared to conduction band electron/O2−• for the removal of the dye. In addition, the photocatalyst exhibited excellent stability and reusability.
Electrocatalytic water splitting (EWS) driven by renewable energy is widely considered an environmentally friendly and sustainable approach for generating hydrogen (H 2 ), an ideal energy carrier for the future. However, the efficiency and economic viability of large‐scale water electrolysis depend on electrocatalysts that can efficiently accelerate the electrochemical reactions taking place at the two electrodes. Wood‐derived nanomaterials are well‐suited for serving as EWS catalysts because of their hierarchically porous structure with high surface area and low tortuosity, compositional tunability, cost‐effectiveness, and self‐standing integral electrode configuration. Here, recent advancements in the design and synthesis of wood‐structured nanomaterials serving as advanced electrocatalysts for water splitting are summarized. First, the design principles and corresponding strategies toward highly effective wood‐structured electrocatalysts (WSECs) are emphasized. Then, a comprehensive overview of current findings on WSECs, encompassing diverse structural designs and functionalities such as supported‐metal nanoparticles (NPs), single‐atom catalysts (SACs), metal compounds, and heterostructured electrocatalysts based on engineered wood hosts are presented. Subsequently, the application of these WSECs in various aspects of water splitting, including the hydrogen evolution reaction (HER), oxygen evolution reaction (OER), overall water splitting (OWS), and hybrid water electrolysis (HWE) are explored. Finally, the prospects, challenges, and opportunities associated with the broad application of WSECs are briefly discussed. This review aims to provide a comprehensive understanding of the ongoing developments in water‐splitting catalysts, along with outlining design principles for the future development of WSECs.
Transition metal diborides represented by MoB2 have attracted widespread attention for their excellent acidic hydrogen evolution reaction (HER). Nevertheless, their electrocatalytic performance is generally unsatisfactory in high‐pH electrolytes. Heterogeneous interface engineering is one of the most promising methods for optimizing the composition and structure of electrocatalysts, thereby greatly affecting their electrochemical performance. Herein, a heterostructure, composed of MoB2 and carbon nanotubes (CNTs), is rationally constructed by boronizing precursors including (NH4)4[NiH6Mo6O24]·5H2O (NiMo6) and Co complexes on the carbon cloth (Co,Ni–MoB2@CNT/CC). In this method, NiMo6 is boronized to form MoB2 by a modified molten‐salt‐assisted borothermal reduction. Meanwhile, Co catalyzes extra carbon sources to grow CNTs on the surface of MoB2. Thanks to the successful production of the heterostructure, Co,Ni–MoB2@CNT/CC exhibits remarkable HER performance with a low overpotential of 98.6, 113.0, and 73.9 mV at 10 mA cm⁻² in acidic, neutral, and alkaline electrolytes, respectively. Notably, even at 500 mA cm⁻², the electrochemical activity of Co,Ni–MoB2@CNT/CC exceeds that of Pt/C/CC in an alkaline solution and maintains over 50 h. Theoretical calculations reveal that the construction of the heterostructure is beneficial to both water dissociation and reactive intermediate adsorption, resulting in superior alkaline HER performance.
Precise morphology design and electronic structure regulation are critically significant to promote catalytic activity and stability for electrochemical hydrogen production at high current density. Herein, the carbon nanotube (CNT) encapsulated Fe‐doped NiCoP nanoparticles is in‐situ grown in hierarchical carbonized wood (NCF0.5P@CNT/CW) for water splitting. Coupling merits of porous carbonized wood (CW) substrate, CNT encapsulating and Fe doping, the NCF0.5P@CNT/CW features remarkable and durable electrocatalytic activity. The overpotentials of NCF0.5P@CNT/CW at 50 mA cm⁻² mV and 205 mV for oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) and features high current density of 800 mA cm⁻² within 300 mV for both OER and HER. Moreover, NCF0.5P@CNT/CW displays outstanding overall water splitting performance (η50 = 1.62 V and η100 = 1.67 V), outperforming Pt/C║RuO2 (η50 = 1.74 V), and can achieve the current density of 700 mA cm⁻² at a lower cell voltage of 1.78 V. Overpotential is only 4.0 % decay after 120 h measurement at 50 mA cm⁻². Density functional theory (DFT) calculations reveals Fe doping optimizes the binding energy and Gibbs free energy of intermediates, and regulates d‐band center of NCF0.5P@CNT/CW. Such synergistic strategy of morphology manipulation and electronic structure optimization provides a spark for developing effective and robust bifunctional catalysts.
In recent years, there has been significant interest in the development of two-dimensional (2D) nanomaterials with unique physicochemical properties for various energy applications. These properties are often derived from the phase structures established through a range of physical and chemical design strategies. A concrete analysis of the phase structures and real reaction mechanisms of 2D energy nanomaterials requires advanced characterization methods that offer valuable information as much as possible. Here, we present a comprehensive review on the phase engineering of typical 2D nanomaterials with the focus of synchrotron radiation characterizations. In particular, the intrinsic defects, atomic doping, intercalation, and heterogeneous interfaces on 2D nanomaterials are introduced, together with their applications in energy-related fields. Among them, synchrotron-based multiple spectroscopic techniques are emphasized to reveal their intrinsic phases and structures. More importantly, various in situ methods are employed to provide deep insights into their structural evolutions under working conditions or reaction processes of 2D energy nanomaterials. Finally, conclusions and research perspectives on the future outlook for the further development of 2D energy nanomaterials and synchrotron radiation light sources and integrated techniques are discussed.
