Photoelectrochemical (PEC) cells for solar‐energy conversion have received immense interest as a promising technology for renewable hydrogen production. Their similarity to natural photosynthesis, ...utilizing sunlight and water, has provoked intense research for over half a century. Among many potential photocatalysts, BiVO4, with a bandgap of 2.4–2.5 eV, has emerged as a highly promising photoanode material with a good chemical stability, environmental inertness, and low cost. Unfortunately, its charge transport properties are modest, at most a hole diffusion length (Lp) of ≈70 nm. However, recent rapid developments in multiple modification strategies have elevated it to a position as the most promising metal oxide photoanode material. This review summarizes developments in BiVO4 photoanodes in the past 10 years, in which time it has continuously broken its own performance records for PEC water oxidation. Effective modification techniques are discussed, including synthesis of nanostructures/nanopores, external/internal doping, heterojunction fabrication, surface passivation, and cocatalysts. Tandem systems for unassisted solar water splitting and PEC production of value‐added chemicals are also discussed.
Elaborately modified BiVO4‐based photoanodes and the evolution of their solar water oxidation photocurrent density are presented.
MoS2 becomes an efficient and durable nonprecious‐metal electrocatalyst for the hydrogen evolution reaction (HER) when it contains multifunctional active sites for water splitting derived from ...1T‐phase, defects, S vacancies, exposed Mo edges with expanded interlayer spacings. In contrast to previously reported MoS2‐based catalysts targeting only a single or few of these characteristics, the all‐in‐one MoS2 catalyst prepared herein features all of the above active site types. During synthesis, the intercalation of in situ generated NH3 molecules into MoS2 sheets affords ammoniated MoS2 (A‐MoS2) that predominantly comprises 1T‐MoS2 and exhibits an expanded interlayer spacing. The subsequent reduction of A‐MoS2 results in the removal of intercalated NH3 and H2S to form an all‐in‐one MoS2 with multifunctional active sites mentioned above (R‐MoS2) that exhibits electrocatalytic HER performance in alkaline media superior to those of all previously reported MoS2‐based electrocatalysts. In particular, a hybrid MoS2/nickel foam catalyst outperforms commercial Pt/C in the practically meaningful high‐current region (>25 mA cm−2), demonstrating that R‐MoS2‐based materials can potentially replace Pt catalysts in practical alkaline HER systems.
Defect‐rich, Mo‐edge‐exposed, S‐deficient, and interlayer‐expanded metallic 1T‐MoS2 (R‐MoS2) electrocatalysts are successfully synthesized using a unique melamine‐phosphomolybdate (MA‐PMo12) supermolecular structure as a precursor. The multifunctional active sites enhance the hydrogen evolution reaction activity of R‐MoS2.
The electrical conduction of polysilicon can be improved through the passivation of defects located at grain boundaries. Most passivation proceeds by hydrogen bonding to dangling bonds of silicon. ...However, more research is needed on the reliability of the Si-H bond. A process using deuterium instead of hydrogen can be expected to improve the performance of silicon devices because Si-D bonds have much higher stability than Si-H bonds. In this study, we have investigated how the isotope effect appears in polysilicon applications. For this purpose, a photodetector composed of a polysilicon film incorporated with hydrogen or deuterium was prepared, and then, current-voltage (<inline-formula> <tex-math notation="LaTeX">{I} </tex-math></inline-formula>-<inline-formula> <tex-math notation="LaTeX">{V} </tex-math></inline-formula>) characteristics, photo response, and degradation thereof were investigated. Hydrogen and deuterium incorporation was performed by both furnace annealing and ion implantation methods. It was found that in order for the isotope effect to occur in polysilicon grain structure, the density of grain boundary must be maintained properly, and there must be no additional damage during the hydrogen or deuterium process. Through this study, it was confirmed that the electrical characteristics and the reliability of the polysilicon based-photodetector were improved by forming a Si-D bond inside the polysilicon with the furnace annealing.
An ultrathin (ca. 2 nm) amorphous FeOOH overlayer was deposited conformally on a hematite nanostructure by a simple solution‐based precipitation method, to generate an oxygen evolution cocatalyst for ...efficient solar water splitting. This uniform and highly conformal coating of the ultrathin metal oxyhydroxide is rare and is distinguished from the layers prepared by other conventional methods. With the FeOOH overlayer as the cocatalyst, the water oxidation photocurrent of hematite increased by a factor of approximately two and the onset potential shifted in the cathodic direction by 0.12 V under 1 sun illumination. The enhanced performance was attributed to the improved water oxidation kinetics and the passivation of the surface states of the hematite.
Skinnymalinks: An ultrathin (ca. 2 nm) amorphous FeOOH overlayer was deposited conformally on a hematite nanostructure by a simple solution‐based precipitation method, to generate an oxygen evolution cocatalyst for efficient solar water splitting. With an FeOOH overlayer, the water oxidation performance of hematite increased as a result of improved water oxidation kinetics and passivation of the surface states.
Photoelectrochemical (PEC) water splitting is a promising way to produce clean and sustainable hydrogen fuel. Solar hydrogen production by using p‐type metal oxide semiconductor photocathodes has not ...been studied as extensively as that with n‐type metal oxide semiconductor photoanodes and p‐type photovoltaic‐grade non‐oxide semiconductor photocathodes. Copper‐based oxide photocathodes show relatively good conductivity, but suffer from instability in aqueous solution under illumination, whereas iron‐based metal oxide photocathodes demonstrate more stable PEC performance but have problems in charge separation and transport. Herein, an overview of recent progress in p‐type metal oxide‐based photocathodes for PEC water reduction is provided. Although these materials have not been fully developed to reach their potential performance, the challenges involved have been identified and strategies to overcome these limitations have been proposed. Future research in this field should address these issues and challenges in addition to the discovery of new materials.
Progressing p‐type performance: An overview of recent progress in the preparation of p‐type metal oxide‐based photocathodes for photoelectrochemical water reduction is provided. Although the materials have not yet reached their full performance potential, the challenges involved have been identified and strategies to overcome the limitations have been proposed.
This study aimed to investigate the biomechanical effects of a newly developed interspinous process device (IPD), called TAU. This device was compared with another IPD (SPIRE) and the pedicle screw ...fixation (PSF) technique at the surgical and adjacent levels of the lumbar spine.
A three-dimensional finite element model analysis of the L1-S1 segments was performed to assess the biomechanical effects of the proposed IPD combined with an interbody cage. Three surgical models-two IPD models (TAU and SPIRE) and one PSF model-were developed. The biomechanical effects, such as range of motion (ROM), intradiscal pressure (IDP), disc stress, and facet loads during extension were analyzed at surgical (L3-L4) and adjacent levels (L2-L3 and L4-L5). The study analyzed biomechanical parameters assuming that the implants were perfectly fused with the lumbar spine.
The TAU model resulted in a 45%, 49%, 65%, and 51% decrease in the ROM at the surgical level in flexion, extension, lateral bending, and axial rotation, respectively, when compared to the intact model. Compared to the SPIRE model, TAU demonstrated advantages in stabilizing the surgical level, in all directions. In addition, the TAU model increased IDP at the L2-L3 and L4-L5 levels by 118.0% and 78.5% in flexion, 92.6% and 65.5% in extension, 84.4% and 82.3% in lateral bending, and 125.8% and 218.8% in axial rotation, respectively. Further, the TAU model exhibited less compensation at adjacent levels than the PSF model in terms of ROM, IDP, disc stress, and facet loads, which may lower the incidence of the adjacent segment disease (ASD).
The TAU model demonstrated more stabilization at the surgical level than SPIRE but less stabilization than the PSF model. Further, the TAU model demonstrated less compensation at adjacent levels than the PSF model, which may lower the incidence of ASD in the long term. The TAU device can be used as an alternative system for treating degenerative lumbar disease while maintaining the physiological properties of the lumbar spine and minimizing the degeneration of adjacent segments.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
The search for earth-abundant materials that can be used in solar water splitting cells remains an important goal for affordable and environmentally friendly methods for energy conversion and ...storage. The stability of photoelectrodes in solar water splitting cells is a major challenge in the development of efficient photoelectrodes. This article reviews state-of-the-art theoretical research activities mainly based on density functional theory (DFT) calculations in the development of efficient photoanode materials, focusing on the scientific and technological possibilities offered by photoanode materials, such as BiVO
4
, α-Fe
2
O
3
, WO
3
, TaON and Ta
3
N
5
. We start with a brief introduction to exploring suitable photoanode materials as well as optimizing their energy band configurations for specific applications. This introduction section is followed by the basic theory of photocatalysis. Finally, we discuss the current theoretical progress in the development of photoanode materials according to the DFT results available in the literature to date. This review also highlights crucial issues that should be addressed in future research activities in the summary and outlook section.
The search for earth-abundant materials that can be used in solar water splitting cells remains an important goal for affordable and environmentally friendly methods for energy conversion and storage.
Ultrasmall Co9S8 nanoparticles are introduced on the basal plane of MoS2 to fabricate a covalent 0D–2D heterostructure that enhances the hydrogen evolution reaction (HER) activity of electrochemical ...water splitting. In the heterostructure, separate phases of Co9S8 and MoS2 are formed, but they are connected by Co–S–Mo type covalent bonds. The charge redistribution from Co to Mo occurring at the interface enhances the electron‐doped characteristics of MoS2 to generate electron‐rich Mo atoms. Besides, reductive annealing during the synthesis forms S defects that activates adjacent Mo atoms for further enhanced HER activity as elucidated by the density functional theory (DFT) calculation. Eventually, the covalent Co9S8–MoS2 heterostructure shows amplified HER activity as well as stability in all pH electrolytes. The synergistic effect is pronounced when the heterostructure is coupled with a porous Ni foam (NF) support to form Co9S8–MoS2/NF that displays superior performance to those of the state‐of‐the‐art non‐noble metal electrocatalysts, and even outperforms a commercial Pt/C catalyst in a practically meaningful, high current density region in alkaline (>170 mA cm−2) and neutral (>60 mA cm−2) media. The high HER performance and stability of Co9S8–MoS2 heterostructure make it a promising pH universal alternative to expensive Pt‐based electrocatalysts for practical water electrolyzers.
Co9S8 nanoparticles grow on the MoS2 sheet via covalent bonds of the Co–S–Mo type. The charge redistribution at the interface makes the Mo sites electron‐rich and abundant S defects on MoS2 activate the inert basal plane. The strong connection and interaction with S defects of 0D–2D heterostructure eventually lead to amplified hydrogen evolution reaction activity as well as stability in all pH electrolytes.
Attenuation correction (AC) is essential for the generation of artifact-free and quantitatively accurate positron emission tomography (PET) images. PET AC based on computed tomography (CT) frequently ...results in artifacts in attenuation-corrected PET images, and these artifacts mainly originate from CT artifacts and PET-CT mismatches. The AC in PET combined with a magnetic resonance imaging (MRI) scanner (PET/MRI) is more complex than PET/CT, given that MR images do not provide direct information on high-energy photon attenuation. Deep-learning (DL)-based methods for the improvement of PET AC have received significant research attention as alternatives to conventional AC methods. Many DL studies were focused on the transformation of MR images into synthetic pseudo-CT or attenuation maps. Alternative approaches that are not dependent on the anatomical images (CT or MRI) can overcome the limitations related to current CT- and MRI-based ACs and allow for more accurate PET quantification in stand-alone PET scanners for the realization of low radiation doses. In this article, a review is presented on the limitations of the PET AC in current dual-modality PET/CT and PET/MRI scanners, in addition to the current status and progress of DL-based approaches, for the realization of improved performance of PET AC.
The electrocatalytic conversion of CO2 to value‐added hydrocarbons is receiving significant attention as a promising way to close the broken carbon‐cycle. While most metal catalysts produce C1 ...species, such as carbon monoxide and formate, the production of various hydrocarbons and alcohols comprising more than two carbons has been achieved using copper (Cu)‐based catalysts only. Methods for producing specific C2 reduction outcomes with high selectivity, however, are not available thus far. Herein, the morphological effect of a Cu mesopore electrode on the selective production of C2 products, ethylene or ethane, is presented. Cu mesopore electrodes with precisely controlled pore widths and depths were prepared by using a thermal deposition process on anodized aluminum oxide. With this simple synthesis method, we demonstrated that C2 chemical selectivity can be tuned by systematically altering the morphology. Supported by computational simulations, we proved that nanomorphology can change the local pH and, additionally, retention time of key intermediates by confining the chemicals inside the pores.
I pity the pore intermediate: Nanomorphology‐directed C2‐product selectivity was demonstrated on a Cu mesopore electrode. A local flow field is generated on the electrode surface and confines reaction intermediates inside the pore. The prolonged retention time of the intermediates affects the kinetics of protonation and C−C bond formation, determining the final C2 product.
PDF
