Converting solar energy into hydrogen via photoelectrochemical (PEC) water splitting is one of the most promising approaches for a sustainable energy supply. Highly active, cost‐effective, and robust ...photoelectrodes are undoubtedly crucial for the PEC technology. To achieve this goal, transition‐metal‐based electrocatalysts have been widely used as cocatalysts to improve the performance of PEC cells for water splitting. Herein, this Review summarizes the recent progresses of the design, synthesis, and application of transition‐metal‐based electrocatalysts as cocatalysts for PEC water splitting. Mo, Ni, Co‐based electrocatalysts for the hydrogen evolution reaction (HER) and Co, Ni, Fe‐based electrocatalysts for the oxygen evolution reaction (OER) are emphasized as cocatalysts for efficient PEC HER and OER, respectively. Particularly, some most efficient and robust photoelectrode systems with record photocurrent density or durability for the half reactions of HER and OER are highlighted and discussed. In addition, the self‐biased PEC devices with high solar‐to‐hydrogen efficiency based on earth‐abundant materials are also addressed. Finally, this Review is concluded with a summary and remarks on some challenges and opportunities for the further development of transition‐metal‐based electrocatalysts as cocatalysts for PEC water splitting.
Photoelectrochemical water splitting for hydrogen production is regarded as a promising way to harvest and store the intermittent solar energy. Highly efficient photoelectrodes require integrating of electrocatalysts onto the light absorbers. In this Review, the recent applications of transition‐metal‐based hydrogen evolution reaction and oxygen evolution reaction electrocatalysts as cocatalyst to be incorporated into photoelectrochemical systems for solar water splitting are summarized.
The conversion and storage of solar energy to chemical energy
artificial photosynthesis holds significant potential for optimizing the energy situation and mitigating the global warming effect. ...Photocatalytic water splitting utilizing particulate semiconductors offers great potential for the production of renewable hydrogen, while this cross-road among biology, chemistry, and physics features a topic with fascinating interdisciplinary challenges. Progress in photocatalytic water splitting has been achieved in recent years, ranging from fundamental scientific research to pioneering scalable practical applications. In this review, we focus mainly on the recent advancements in terms of the development of new light-absorption materials, insights and strategies for photogenerated charge separation, and studies towards surface catalytic reactions and mechanisms. In particular, we emphasize several efficient charge separation strategies such as surface-phase junction, spatial charge separation between facets, and polarity-induced charge separation, and also discuss their unique properties including ferroelectric and photo-Dember effects on spatial charge separation. By integrating time- and space-resolved characterization techniques, critical issues in photocatalytic water splitting including photoinduced charge generation, separation and transfer, and catalytic reactions are analyzed and reviewed. In addition, photocatalysts with state-of-art efficiencies in the laboratory stage and pioneering scalable solar water splitting systems for hydrogen production using particulate photocatalysts are presented. Finally, some perspectives and outlooks on the future development of photocatalytic water splitting using particulate photocatalysts are proposed.
Precise control over the size, shape, composition, structure, and crystal phase of random alloy and intermetallic nanocrystals has been intensively explored in technologically important applications ...in recent years. Different from the monometallic nanocrystals and other types of structural nanocrystals such as core–shell and heterostructured nanocrystals, well-defined multimetallic random alloy and intermetallic nanocrystals exhibit unique and intriguing physicochemical properties, serving as ideal models for benefiting the structure-to-property studies. As such, random alloy and intermetallic nanocrystals have attracted extensive attention and interest in scientific research and shown huge potential in various fields. In this review, we focus specifically on summarizing the synthetic principles and strategies developed to form random alloy and intermetallic nanocrystals with enhanced performance. Some representative examples are purposely selected for emphasizing basic concepts and mechanistic understanding. We then highlight the fascinating properties and widespread applications of random alloy and intermetallic nanocrystals in electrocatalysis, heterogeneous catalysis, optical and photocatalysis, as well as magnetism and conclude the review by addressing the prospects and current challenges for the controlled synthesis of random alloy and intermetallic nanocrystals.
Fatty acid oxidation (FAO) dysfunction is one of the important mechanisms of renal fibrosis. Sirtuin 3 (Sirt3) has been confirmed to alleviate acute kidney injury (AKI) by improving mitochondrial ...function and participate in the regulation of FAO in other disease models. However, it is not clear whether Sirt3 is involved in regulating FAO to improve the prognosis of AKI induced by cisplatin. Here, using a murine model of cisplatin‐induced AKI, we revealed that there were significantly FAO dysfunction and extensive lipid deposition in the mice with AKI. Metabolomics analysis suggested reprogrammed energy metabolism and decreased ATP production. In addition, fatty acid deposition can increase reactive oxygen species (ROS) production and induce apoptosis. Our data suggested that Sirt3 deletion aggravated FAO dysfunction, resulting in increased apoptosis of kidney tissues and aggravated renal injury. The activation of Sirt3 by honokiol could improve FAO and renal function and reduced fatty acid deposition in wide‐type mice, but not Sirt3‐defective mice. We concluded that Sirt3 may regulate FAO by deacetylating liver kinase B1 and activating AMP‐activated protein kinase. Also, the activation of Sirt3 by honokiol increased ATP production as well as reduced ROS and lipid peroxidation through improving mitochondrial function. Collectively, these results provide new evidence that Sirt3 is protective against AKI. Enhancing Sirt3 to improve FAO may be a potential strategy to prevent kidney injury in the future.
Photogenerated charge separation is one of the key factors determining the solar energy conversion efficiency in photocatalysis and photoelectrocatalysis. Fabrication of phase junction has been ...demonstrated to be an effective strategy to construct the internal electric field for the charge separation. Phase junction is essentially a heterojunction, but more common in semiconductor-based photoelectric conversion systems, because most semiconductors exhibit the polymorphous structures. Because of the similar crystal structure between the two phases, phase junctions are more easily formed. The application of phase junction in photocatalysis and photoelectrocatalysis, especially the anatase–rutile TiO2 and α–β Ga2O3 phase junction, are summarized in this Feature Article. The internal electrical field across the phase junction provides enough driving force for the improved charge separation, evidenced by the time and spatial resolved characterizations. We conclude with a summary and perspectives on the design and application of phase junction in solar energy conversion systems.
Since the 1970s, splitting water using solar energy has been a focus of great attention as a possible means for converting solar energy to chemical energy in the form of clean and renewable hydrogen ...fuel. Approaches to solar water splitting include photocatalytic water splitting with homogeneous or heterogeneous photocatalysts, photoelectrochemical or photoelectrocatalytic (PEC) water splitting with a PEC cell, and electrolysis of water with photovoltaic cells coupled to electrocatalysts. Though many materials are capable of photocatalytically producing hydrogen and/or oxygen, the overall energy conversion efficiency is still low and far from practical application. This is mainly due to the fact that the three crucial steps for the water splitting reaction: solar light harvesting, charge separation and transportation, and the catalytic reduction and oxidation reactions, are not efficient enough or simultaneously. Water splitting is a thermodynamically uphill reaction, requiring transfer of multiple electrons, making it one of the most challenging reactions in chemistry. This Account describes the important roles of cocatalysts in photocatalytic and PEC water splitting reactions. For semiconductor-based photocatalytic and PEC systems, we show that loading proper cocatalysts, especially dual cocatalysts for reduction and oxidation, on semiconductors (as light harvesters) can significantly enhance the activities of photocatalytic and PEC water splitting reactions. Loading oxidation and/or reduction cocatalysts on semiconductors can facilitate oxidation and reduction reactions by providing the active sites/reaction sites while suppressing the charge recombination and reverse reactions. In a PEC water splitting system, the water oxidation and reduction reactions occur at opposite electrodes, so cocatalysts loaded on the electrode materials mainly act as active sites/reaction sites spatially separated as natural photosynthesis does. In both cases, the nature of the loaded cocatalysts and their interaction with the semiconductor through the interface/junction are important. The cocatalyst can provide trapping sites for the photogenerated charges and promote the charge separation, thus enhancing the quantum efficiency; the cocatalysts could improve the photostability of the catalysts by timely consuming of the photogenerated charges, particularly the holes; most importantly, the cocatalysts catalyze the reactions by lowering the activation energy. Our research shows that loading suitable dual cocatalysts on semiconductors can significantly increase the photocatalytic activities of hydrogen and oxygen evolution reactions, and even make the overall water splitting reaction possible. All of these findings suggest that dual cocatalysts are necessary for developing highly efficient photocatalysts for water splitting reactions.
Precise control of the morphology and crystalline structure of semiconductor-based photocatalyst is crucial for improving the efficiency of solar energy conversion system. In this work, taking BiVO4 ...semiconductor photocatalyst as an example, we investigated the formation process for the regular decahedron BiVO4 crystals prepared by a convenient hydrothermal method and found that the synthesis is undergoing a dissolution–recrystallization process, concomitantly, the phase was transformed from tetragonal zircon type to monoclinic sheelite-type. By controlling the kinetics of crystal growth for BiVO4 through regulating acidity of the reaction solution, we rationally tune the morphology of monoclinic BiVO4 from regular decahedron crystals to short rod-like particles, particularly precisely modulate the proportion of {010}/{011} facets for the decahedron BiVO4. By tuning the crystalline phase and morphologies of BiVO4 crystal, we found that the photocatalytic water oxidation activity for the well-defined BiVO4 crystal with specific configuration of {010} and {011} exposed facets can be 50 times of tetragonal BiVO4 particles. Our work shows a convenient strategy for precise control of the growth process of semiconductor-based photocatalyst, based on the understanding of the crystal morphology evolution mechanism, which will be instructive for constructing semiconductor-based photocatalysts for solar energy conversion.
The efficiency of photoelectrocatalytic (PEC) water splitting is limited by the serious recombination of photogenerated charges, high overpotential, and sluggish kinetics of surface reaction. Herein ...we describe the recent progress on engineering the electrode–electrolyte and semiconductor–cocatalyst interfaces with cocatalysts, electrolytes, and interfacial layers (interlayers) to increase the PEC efficiency. Introducing cocatalysts has been demonstrated to be the most efficient way to lower the reaction barrier and promote charge injection to the reactants. In addition, it has been found that electrolyte ions can influence the surface catalysis remarkably. Electrolyte cations on the surface can influence the water splitting and backward reactions, and anions may take part in the proton transfer processes, indicating that fine-tuning of the electrolyte parameters turns out to be an important strategy for enhancing the PEC efficiency. Moreover, careful modification of the interface between the cocatalysts and the semiconductor via suitable interlayers is critical for promoting charge separation and transfer, which can indirectly influence the surface catalysis. The mechanisms of surface catalysis are assumed to involve transfer of photogenerated holes to the surface active sites to form high-valent species, which then oxidize the water molecules. Many key scientific issues about the generation of photovoltage, the separation, storage, and transfer of carriers, the function of cocatalysts, the roles of electrolyte ions, and the influences of other parameters during PEC water splitting will be discussed in detail with some perspective views.
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•An electrochemical sensor for SARS-CoV-2 was constructed based on a smartphone.•The signal amplification of the sensor was based on supersandwich-type recognition strategy.•The ...detectable ratios of the sensor were higher than those obtained by RT-qPCR.•The sensor has the lowest limit of detection among the published approaches to date.•The sensor showed high specificity and selectivity.
The recent pandemic outbreak of COVID-19 caused by a novel severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), poses a threat to public health globally. Thus, developing a rapid, accurate, and easy-to-implement diagnostic system for SARS-CoV-2 is crucial for controlling infection sources and monitoring illness progression. Here, we reported an ultrasensitive electrochemical detection technology using calixarene functionalized graphene oxide for targeting RNA of SARS-CoV-2. Based on a supersandwich-type recognition strategy, the technology was confirmed to practicably detect the RNA of SARS-CoV-2 without nucleic acid amplification and reverse-transcription by using a portable electrochemical smartphone. The biosensor showed high specificity and selectivity during in silico analysis and actual testing. A total of 88 RNA extracts from 25 SARS-CoV-2-confirmed patients and eight recovery patients were detected using the biosensor. The detectable ratios (85.5 % and 46.2 %) were higher than those obtained using RT-qPCR (56.5 % and 7.7 %). The limit of detection (LOD) of the clinical specimen was 200 copies/mL, which is the lowest LOD among the published RNA measurement of SARS-CoV-2 to date. Additionally, only two copies (10 μL) of SARS-CoV-2 were required for per assay. Therefore, we developed an ultrasensitive, accurate, and convenient assay for SARS-CoV-2 detection, providing a potential method for point-of-care testing.
A new topological crystalline insulator material, SnSe in the rock‐salt structure, is obtained using molecular beam epitaxy. The thermodynamically unstable rock‐salt SnSe phase is stabilized in ...epitaxial films up to 20 nm by a Bi2Se3 substrate. Dirac surface states are observed at both the Γ¯ and the M¯ points using angle‐resolved photoemission spectroscopy; this confirms the topological crystalline insulator phase of the films.
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