Three-Dimensional FTO/TiO₂/BiVO₄ Composite Inverse Opals Photoanode with Excellent Photoelectrochemical Performance

A poor electron transport property, short charge carrier diffusion lengths, and slow water oxidation kinetics severely limit the photoelectrochemical (PEC) performance of the BiVO₄ photoelectrodes. To address these problems, we report the design and fabrication of a three-dimensional FTO/TiO₂/BiVO₄ core–shell inverse opals photoanode for PEC hydrogen production by combining atomic layer deposition and electrodeposition routes for TiO₂ and BiVO₄ layer deposition on F:SnO₂ (FTO) inverse opal skeletons, respectively. Benefiting from the highly conductive transparent FTO invese opal networks providing fast electron pathways and TiO₂/BiVO₄ heterojunctions, the as-fabricated 3D FTO/TiO₂/BiVO₄ inverse opals photoanode delivers excellent PEC performance with a maximum photocurrent density of 4.11 mA/cm² at 1.23 V vs a reversible hydrogen electrode in the presence of a hole scavenger in contrast to that of the counterparts FTO/TiO₂ and FTO/BiVO₄ inverse opals electrodes, respectively, which could be attributed to the significantly improved charge transport and separation efficiency

ALD TiO₂‑Coated Flower-like MoS₂ Nanosheets on Carbon Cloth as Sodium Ion Battery Anode with Enhanced Cycling Stability and Rate Capability

We report the fabrication of 3D flower-like MoS₂ nanosheets arrays on carbon cloth as a binder-free anode for sodium ion battery. Ultrathin and conformal TiO₂ layers are used to modify the surface of MoS₂ by atomic layer deposition. The electrochemical performance measurements demonstrate that the ALD TiO₂ layer can improve the cycling stability and rate capability of MoS₂. The MoS₂ nanosheets with 0.5-nm TiO₂ coating electrode show the highest initial discharge capacity of 1392 mA h g^–1 at 200 mA g^–1, which is increased by 53% compared with that of bare MoS₂. After 150 cycles, the capacity retention rate of the TiO₂-coated MoS₂ achieves 75.8% of its second cycle’s capacity at 200 mA h g^–1 in contrast to that of 59% of pure MoS₂. Furthermore, the mechanism behind the experimental results is revealed by ex situ scanning electron microscope (SEM), X-ray powder diffraction (XRD), and electrochemical impedance spectroscopy (EIS) characterizations, which confirms that the ultrathin TiO₂ modifications can prevent the structural degradation and the formation of SEI film of MoS₂ electrode

Three-Dimensional CdS-Sensitized Sea Urchin Like TiO₂‑Ordered Arrays as Efficient Photoelectrochemical Anodes

We demonstrate the fabrication of a 3D ordered sea urchin like TiO₂ structure by combining colloidal spheres template, atomic layer deposition (ALD), and hydrothermal growth method. The 3D sea urchin like TiO₂ arrays as photoanode present improved photoelectrochemical performance in contrast to 2D TiO₂ hollow microspheres and 1D TiO₂ nanowires arrays. With CdS quantum dots sensitization, the sea urchin like TiO₂ array photoanode yields a photocurrent of 5.4 mA cm^–2 at 0 V vs Ag/AgCl. The performance improvement is attributed to the increased specific surface area and porosity, light trapping effect by multiscattering of the hierarchical structure, as well as direct charge transportation paths from the nanorods to the microspheres

Three-dimensional Ordered Macroporous Flexible Electrode Design toward High-Performance Zinc-Ion Batteries

Flexible zinc-ion batteries (ZIBs) have been considered to have huge potential in portable and wearable electronics due to their high safety, cost efficiency, and considerable energy density. Therein, the design and construction of flexible electrodes significantly determine the performance and lifespan of flexible battery devices. In this work, an ultrathin flexible three-dimensional ordered macroporous (3DOM) Sn@Zn anode (60 μm in thickness) is presented to relieve dendrite growth and expand the lifespan of flexible ZIBs. The 3DOM structure can ensure uniform electric field distribution, guide oriented zinc plating/stripping, and extend the lifespan of anodes. The rich zincophilic Sn sites on the electrode surface significantly facilitate Zn nucleation. Accordingly, a lowered nucleation overpotential of 8.9 mV and an ultralong cycling performance of 2400 h at 0.1 mA cm–2 and 0.1 mAh cm–2 are achieved in symmetric cells, and the 3DOM Sn@Zn anode can also operate in deep cycling for over 200 h at 10 mA cm–2 and 5 mAh cm–2. A flexible 3DOM MnO2/Ni cathode with a high structural stability and a high mass-specific capacity is fabricated to match with the anode to form a flexible ZIB with a total thickness of 200 μm. The flexible device delivers a high volumetric energy density of 11.76 mWh cm–3 at 100 mA gMnO2–1 and a high average open-circuit voltage of 1.5 V and exhibits high-performance power supply under deformation in practical application scenarios. This work may shed some light on the design and fabrication of flexible energy-storage devices

Three-Dimensional NiCo₂O₄@Polypyrrole Coaxial Nanowire Arrays on Carbon Textiles for High-Performance Flexible Asymmetric Solid-State Supercapacitor

In this article, we report a novel electrode of NiCo₂O₄ nanowire arrays (NWAs) on carbon textiles with a polypyrrole (PPy) nanosphere shell layer to enhance the pseudocapacitive performance. The merits of highly conductive PPy and short ion transport channels in ordered NiCo₂O₄ mesoporous nanowire arrays together with the synergistic effect between NiCo₂O₄ and PPy result in a high specific capacitance of 2244 F g^–1, excellent rate capability, and cycling stability in NiCo₂O₄/PPy electrode. Moreover, a lightweight and flexible asymmetric supercapacitor (ASC) device is successfully assembled using the hybrid NiCo₂O₄@PPy NWAs and activated carbon (AC) as electrodes, achieving high energy density (58.8 W h kg^–1 at 365 W kg^–1), outstanding power density (10.2 kW kg^–1 at 28.4 W h kg^–1) and excellent cycling stability (∼89.2% retention after 5000 cycles), as well as high flexibility. The three-dimensional coaxial architecture design opens up new opportunities to fabricate a high-performance flexible supercapacitor for future portable and wearable electronic devices

Composition-Graded Zn_<i>x</i>Cd_{_1–<i>x</i>}Se@ZnO Core–Shell Nanowire Array Electrodes for Photoelectrochemical Hydrogen Generation

One-dimensional oxide nanostructure arrays are widely investigated as photoelectrodes in solar cells or photoelectrochemical (PEC) solar hydrogen generation applications, for which it is highly desirable for the electrode to have a broad light absorption and an efficient charge separation. In this work, a composition-graded Zn_<i>x</i>Cd_1–<i>x</i>Se@ZnO core–shell nanowire array is prepared through temperature-gradient chemical vapor deposition (CVD) of Zn_<i>x</i>Cd_1–<i>x</i>Se layer onto the pregrown ZnO nanowires. The core–shell nanowire array photoelectrodes yield a continuous absorption edge from 2.7 (460 nm) to 1.77 eV (700 nm) across the sample surface. The core–shell heterostructure facilitates the photogenerated electron–hole pair separation and the electron transfer from ZnCdSe to ZnO. By using such core–shell nanowire arrays as photoanodes for solar hydrogen generation via a PEC cell, a photocurrent density of ∼5.6 mA/cm² is achieved under 1 sun solar light illumination at zero bias versus Ag/AgCl. This method may be useful in the design of multijunction nanostructured semiconductor photoelectrodes toward more efficient solar fuel devices