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•Ammonia synthesis through electrochemical nitrate reduction was summarized.•Mechanisms in electrochemical nitrate reduction to ammonia were briefly discussed.•Electrocatalysts used ...for nitrate reduction to ammonia were introduced.•Guidance can be provided for the design and development of advanced electrocatalysts.
Nitrate (NO3-) pollution has become increasingly prominent due to industry and agriculture. Electrochemical reduction can convert NO3- into high value-added ammonia (NH3) and remove NO3- pollution. This review focuses on the latest research progress in the field of electrochemical nitrate reduction reaction (NO3-RR) to NH3. The mechanism of NO3-RR is briefly discussed. Catalysts, as well as qualitative and quantitative methods for the detection of NH3 are also summarized. Finally, the challenges and prospects in this field are discussed. We hope this mini review aids researchers in the design and development of advanced research strategies for electrochemical NO3--to-NH3 processes.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Carbon dots (CDs) have attracted much attention due to their excellent photoelectric properties and potential applications. Although previous studies have shown that almost all organic molecules can ...be converted into CDs via chemical carbonization, the mechanism of the conversion process remains unclear. The hydrothermal/solvothermal method commonly used to prepare CDs is complicated and leads to the generation of many by-product CDs with similar structures. Considering that the purification of the synthesized by-products is difficult, the process of CDs formation cannot be readily analyzed and understood. Herein, we use ethanol as a carbon source to synthesize white-emitting CDs (W-CDs). Column chromatography separation shows that the synthesized W-CDs are composed of blue-, cyan-, and yellow-emitting CDs that fluoresce at wavelengths corresponding to the three emission centers of W-CDs. Although the samples have similar graphitic structure, they exhibit different surface states due to variations in the degree of oxidation and carbonization. Therefore, the red-shift in their emission peaks is attributed to an increased degree of carbonization in their polymer structure. Theoretical calculations verify the experimental results, and the prepared CDs are successfully used to develop multi-color and white light-emitting diodes (LEDs).
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
The Visual Question Answering (VQA) system is the process of finding useful information from images related to the question to answer the question correctly. It can be widely used in the fields of ...visual assistance, automated security surveillance, and intelligent interaction between robots and humans. However, the accuracy of VQA has not been ideal, and the main difficulty in its research is that the image features cannot well represent the scene and object information, and the text information cannot be fully represented. This paper used multi-scale feature extraction and fusion methods in the image feature characterization and text information representation sections of the VQA system, respectively to improve its accuracy. Firstly, aiming at the image feature representation problem, multi-scale feature extraction and fusion method were adopted, and the image features output of different network layers were extracted by a pre-trained deep neural network, and the optimal scheme of feature fusion method was found through experiments. Secondly, for the representation of sentences, a multi-scale feature method was introduced to characterize and fuse the word-level, phrase-level, and sentence-level features of sentences. Finally, the VQA model was improved using the multi-scale feature extraction and fusion method. The results show that the addition of multi-scale feature extraction and fusion improves the accuracy of the VQA model.
The detection of glucose has important significance in clinical medicine and the food industry, especially in the diagnosis of diabetes. In recent years, electrochemical non-enzymatic glucose sensors ...have attracted intensive attention to detect the glucose level with great progress. In this review, we summarize a variety of non-enzymatic glucose sensor materials, including precious metals Pt, Au and their alloy metals, non-precious transition metals and their metal oxides, composites and other functional materials. Moreover, fundamental insights into the reaction mechanism and influencing factors of materials are given. Finally, this review discusses the perspectives and challenges of future developments in electrochemical non-enzymatic glucose detection.
This review summarizes recent advances in the development of electrocatalysts for non-enzymatic glucose detection. The sensing mechanism and influencing factors are discussed, and the perspectives and challenges are also addressed.
Electrochemical nitrogen reduction reaction (NRR) is considered as an alternative to the industrial Haber-Bosch process for NH
3
production due to both low energy consumption and environment ...friendliness. However, the major problem of electrochemical NRR is the unsatisfied efficiency and selectivity of electrocatalyst. As one group of the cheapest and most abundant transition metals, iron-group (Fe, Co, Ni and Cu) electrocatalysts show promising potential on cost and performance advantages as ideal substitute for traditional noble-metal catalysts. In this minireview, we summarize recent advances of iron-group-based materials (including their oxides, hydroxides, nitrides, sulfides and phosphides, etc.) as non-noble metal electrocatalysts towards ambient N
2
-to-NH
3
conversion in aqueous media. Strategies to boost NRR performances and perspectives for future developments are discussed to provide guidance for the field of NRR studies.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
A challenging but pressing task to design and synthesize novel, efficient, and robust pH‐universal hydrogen evolution reaction (HER) electrocatalysts for scalable and sustainable hydrogen production ...through electrochemical water splitting. Herein, we report a facile method to prepare an efficient and robust Ru‐M (M=Ni, Mn, Cu) bimetal nanoparticle and carbon quantum dot hybrid (RuM/CQDs) for pH‐universal HER. The RuNi/CQDs catalysts exhibit outstanding HER performance at all pH levels. The unexpected low overpotentials of 13, 58, and 18 mV shown by RuNi/CQDs allow a current density of 10 mA cm−2 in 1 m KOH, 0.5 m H2SO4, and 1 m PBS, respectively, for Ru loading at 5.93 μgRu cm−2. This performance is among the best catalytic activities reported for any platinum‐free electrocatalyst. Theoretical studies reveal that Ni doping results in a moderate weakening of the hydrogen bonding energy of nearby surface Ru atoms, which plays a critical role in improving the HER activity.
How low can Ru go: A scalable and general synthetic method for the preparation of transition‐metal‐doped RuM/carbon quantum dots (CQDs; M=Ni, Mn, Cu) has been developed through metal‐mediated CQD condensation and carbonization. The low‐ruthenium‐content RuM/CQD catalysts exhibit outstanding activity and stability in catalyzing hydrogen evolution at all pH values.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Recently, heterogeneous photocatalysts have achieved much interest on account of their great potential applications in resolving many tough energy and environmental troubles around the world through ...an ecologically sustainable way. Heterogeneous nanocomposites composed of graphitic carbon nitride (g‐C3N4) and carbon dots (CDs) possess broad spectrum absorption, appropriate electronic band structures, rapid carrier mobility, abundant reserves, excellent chemical stability, and facile synthesis methods, which make them promising composite photocatalysts for suitable applications such as photocatalytic solar fuels production and contaminant decomposition. With the rapid development in photocatalysis by hybridization of g‐C3N4 and CDs, a systematic summary and prospection of performance improvement are urgent and meaningful. This review first focuses on various kinds of effectively synthetic methods of composites. Following, the strategies available for enhanced performance, including morphology optimization, spectral absorption improvement, ternary or quaternary composition hybrid, lateral or vertical heterostructures construction, heteroatom doping, and so forth, are fully discussed. Then, the applications mainly in efficient photocatalytic hydrogen generation, photocatalytic carbon dioxide reduction, and organic pollutants degradation are systematically demonstrated. Finally, the remaining issues and prospect of further development are proposed as some kind of guidance for powerful combination of g‐C3N4 and CDs with high efficiency to photocatalysis.
This review summarizes the recent progress of heterogeneous photocatalysts of g‐C3N4/carbon dot (CD)‐based nanocomposites and their applications mainly in efficient catalytic hydrogen generation, photocatalytic carbon dioxide reduction, and organic pollutants degradation. Finally, the challenges and opportunities for g‐C3N4/CD‐based photocatalysts are critically discussed to offer insight of this field.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
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•The principles of thermal promotion in photocatalysis were discussed.•The common thermal input patterns were summarized.•Thermally-assisted photocatalytic strategies in CO2 reduction ...were reviewed.•Challenges and prospects of thermally-assisted photocatalytic CO2 reduction were given.
Using heat or radiation as a single driving force for implementing carbon dioxide (CO2) conversion is usually limited by sluggish kinetics. Whereas the thermally-assisted photocatalysis by coupling utilization of solar energy and thermal energy has therefore provided a promising alternative strategy to boost the conversion of CO2 into high value-added synthetic fuels or chemicals under mild conditions. Herein, we will focus on the state-of-the-art advance in CO2 reduction to fuels by thermally-assisted photocatalysis, with emphases on the thermally-promoted principles, the thermal input patterns as well as the product distributions of CO2 reduction. In addition, some current challenges and perspectives will be discussed. This review not only gives a comprehensive and in-depth understanding of thermally-assisted photocatalytic CO2 reduction, but provides guidelines to other catalytic transformations (e.g. methane oxidation, nitrogen fixation, and organic coupling reactions) by integrating solar and thermal energy to enhance the reaction efficiency.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
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•This article summarizes the significant advances achieved in the past few years on synthesis, classification, mechanism and applications of CDs and CDs-based photocatalysts to give a ...thorough summary.•CDs-derived photocatalysts are devided into pure CDs and CDs composite photocatalysts and the photocatalytic efficiencies are compared.•Various kinds of mechanism during photocatalytic process in typical systems are concluded.•Applications in the fields of degradation of organics, water splitting for H2 and O2 evolution, CO2 conversion and photocatalytic chemical reactions are also reviewed to confirm the great potential of CDs-derived photocatalysts for environmental and energy issues.
With the rapid development of science and technology, environmental pollution and energy shortage become more and more prominent. To solve these problems, photocatalytic technology is regarded as one of the most efficient methods, allowing for both pollutant degradation and energy conversion. Compared with traditional group IIVI, IIIV quantum dots (QDs), carbon dots (CDs), as a newly emerging kind of fluorescent carbon-based material, possess many excellent properties, such as high aqueous solubility, low cost, low toxicity, abundant surface functional groups and good biocompatibility. In particular, the unique up-converted photoluminescence (PL) behavior and photo-induced electron transfer ability of CDs provide the new route to achieve efficient metal-free photocatalysts. This article reviews recent progress on CDs utilized for photocatalysis from different perspectives, including the following three parts: classification and synthesis, mechanism of CDs-derived photocatalysts as well as the applications for environmental issues (up-converted PL process) and energy conversion (photo-induced electron transfer process).
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
Designing bifunctional catalysts capable of driving the electrochemical hydrogen evolution reaction (HER) and also H2 evolution via the hydrolysis of hydrogen storage materials such as ammonia borane ...(AB) is of considerable practical importance for future hydrogen economies. Herein, we systematically examined the effect of tensile lattice strain in CoRu nanoalloys supported on carbon quantum dots (CoRu/CQDs) on hydrogen generation by HER and AB hydrolysis. By varying the Ru content, the lattice parameters and Ru‐induced lattice strain in the CoRu nanoalloys could be tuned. The CoRu0.5/CQDs catalyst with an ultra‐low Ru content (1.33 wt.%) exhibited excellent catalytic activity for HER (η=18 mV at 10 mA cm−2 in 1 M KOH) and extraordinary activity for the hydrolysis of AB with a turnover frequency of 3255.4 mol(H2)
mol−1(Ru) min−1 or 814.7 mol(H2)
mol−1(cat) min−1 at 298 K, respectively, representing one of the best activities yet reported for AB hydrolysis over a ruthenium alloy catalyst. Moreover, the CoRu0.5/CQDs catalyst displayed excellent stability during each reaction, including seven alternating cycles of HER and AB hydrolysis. Theoretical calculations revealed that the remarkable catalytic performance of CoRu0.5/CQDs resulted from the optimal alloy electronic structure realized by incorporating small amounts of Ru, which enabled fast interfacial electron transfer to intermediates, thus benefitting H2 evolution kinetics. Results support the development of new and improved catalysts HER and AB hydrolysis.
Ultra‐low Ru induced CoRu nanoalloy lattice strain for robust hydrogen evolution reaction (HER) and hydrolysis of ammonia borane (AB) bifunctional hydrogen production is introduced. The CoRu0.5/CQDs displayed excellent stability during each reaction, including seven alternating cycles of HER and AB hydrolysis.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
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