Rate-dependent morphology of Li2O2 growth in Li-O2 batteries

Compact solid discharge products enable energy storage devices with high gravimetric and volumetric energy densities, but solid deposits on active surfaces can disturb charge transport and induce mechanical stress. In this Letter we develop a nanoscale continuum model for the growth of Li2O2 crystals in lithium-oxygen batteries with organic electrolytes, based on a theory of electrochemical non-equilibrium thermodynamics originally applied to Li-ion batteries. As in the case of lithium insertion in phase-separating LiFePO4 nanoparticles, the theory predicts a transition from complex to uniform morphologies of Li2O2 with increasing current. Discrete particle growth at low discharge rates becomes suppressed at high rates, resulting in a film of electronically insulating Li2O2 that limits cell performance. We predict that the transition between these surface growth modes occurs at current densities close to the exchange current density of the cathode reaction, consistent with experimental observations.Comment: 8 pages, 6 fig

Salicylate method for ammonia quantification in nitrogen electroreduction experiments: The correction of iron III interference

[EN] The salicylate method is one of the ammonia quantification methods that has been extensively used in literature for quantifying ammonia in the emerging field of nitrogen (electro)fixation. The presence of iron in the sample causes a strong negative interference on the salicylate method. Today, the recommended method to deal with such interferences is the experimental correction method: the iron concentration in the sample is measured using an iron quantification method, and then the corresponding amount of iron is added to the calibration samples. The limitation of this method is that when a batch of samples presents a great iron concentration variability, a different calibration curve has to be obtained for each sample. In this work, the interference of iron III on the salicylate method was experimentally quantified, and a model was proposed to capture the effect of iron III interference on the ammonia quantification result. This model can be used to correct the iron III interferences on ammonia quantification. The great advantage of this correction method is that it only requires three experimental curves in order to correct the iron III interference in any sample provided the iron III concentration is below the total peak suppression concentration.This work was supported by the Toyota Research Institute through the Accelerated Materials Design and Discovery program. This work made use of the MRSEC Shared Experimental Facilities at MIT (SEM) supported by the National Science Foundation under award number DMR-1419807 as well as the HZDR Ion Beam Center TEM facilities. J.J.G.S. is very grateful to the Generalitat Valenciana and to the European Social Fund, for their economic support in the form of Vali+d postdoctoral grant (APOSTD-2018-001). G.M.L. was partially supported by a Natural Sciences and Engineering Research Council of Canada (NSERC) PGS-D.Giner-Sanz, JJ.; Leverick, G.; Pérez-Herranz, V.; Shao-Horn, Y. (2020). Salicylate method for ammonia quantification in nitrogen electroreduction experiments: The correction of iron III interference. Journal of The Electrochemical Society. 167(13):1-10. https://doi.org/10.1149/1945-7111/abbdd6S11016713Kibsgaard, J., Nørskov, J. K., & Chorkendorff, I. (2019). The Difficulty of Proving Electrochemical Ammonia Synthesis. ACS Energy Letters, 4(12), 2986-2988. doi:10.1021/acsenergylett.9b02286Wang, Q., Guo, J., & Chen, P. (2020). The Power of Hydrides. Joule, 4(4), 705-709. doi:10.1016/j.joule.2020.02.008Wang, Y., Shi, M., Bao, D., Meng, F., Zhang, Q., Zhou, Y., … Jiang, Q. (2019). Generating Defect‐Rich Bismuth for Enhancing the Rate of Nitrogen Electroreduction to Ammonia. Angewandte Chemie International Edition, 58(28), 9464-9469. doi:10.1002/anie.201903969Andersen, S. Z., Čolić, V., Yang, S., Schwalbe, J. A., Nielander, A. C., McEnaney, J. M., … Chorkendorff, I. (2019). A rigorous electrochemical ammonia synthesis protocol with quantitative isotope measurements. Nature, 570(7762), 504-508. doi:10.1038/s41586-019-1260-xKim, K., Lee, N., Yoo, C.-Y., Kim, J.-N., Yoon, H. C., & Han, J.-I. (2016). Communication—Electrochemical Reduction of Nitrogen to Ammonia in 2-Propanol under Ambient Temperature and Pressure. Journal of The Electrochemical Society, 163(7), F610-F612. doi:10.1149/2.0231607jesMurakami, T., Nishikiori, T., Nohira, T., & Ito, Y. (2005). Investigation of Anodic Reaction of Electrolytic Ammonia Synthesis in Molten Salts Under Atmospheric Pressure. Journal of The Electrochemical Society, 152(5), D75. doi:10.1149/1.1874752Yang, J., Li, T., Zhong, C., Guan, X., & Hu, C. (2016). Nitrogen Fixation in Water Using Air Phase Gliding Arc Plasma. Journal of The Electrochemical Society, 163(10), E288-E292. doi:10.1149/2.0221610jesWang, P., Chang, F., Gao, W., Guo, J., Wu, G., He, T., & Chen, P. (2016). Breaking scaling relations to achieve low-temperature ammonia synthesis through LiH-mediated nitrogen transfer and hydrogenation. Nature Chemistry, 9(1), 64-70. doi:10.1038/nchem.2595Nash, J., Yang, X., Anibal, J., Wang, J., Yan, Y., & Xu, B. (2017). Electrochemical Nitrogen Reduction Reaction on Noble Metal Catalysts in Proton and Hydroxide Exchange Membrane Electrolyzers. Journal of The Electrochemical Society, 164(14), F1712-F1716. doi:10.1149/2.0071802jesWang, Q., Guo, J., & Chen, P. (2019). Recent progress towards mild-condition ammonia synthesis. Journal of Energy Chemistry, 36, 25-36. doi:10.1016/j.jechem.2019.01.027Li, D., Xu, X., Li, Z., Wang, T., & Wang, C. (2020). Detection methods of ammonia nitrogen in water: A review. TrAC Trends in Analytical Chemistry, 127, 115890. doi:10.1016/j.trac.2020.115890Searle, P. L. (1984). The berthelot or indophenol reaction and its use in the analytical chemistry of nitrogen. A review. The Analyst, 109(5), 549. doi:10.1039/an9840900549Song, Y., Johnson, D., Peng, R., Hensley, D. K., Bonnesen, P. V., Liang, L., … Rondinone, A. J. (2018). A physical catalyst for the electrolysis of nitrogen to ammonia. Science Advances, 4(4). doi:10.1126/sciadv.1700336Ivancic, I. (1984). An optimal manual procedure for ammonia analysis in natural waters by the indophenol blue method. Water Research, 18(9), 1143-1147. doi:10.1016/0043-1354(84)90230-6Ayyub, O. B., Behrens, A. M., Heligman, B. T., Natoli, M. E., Ayoub, J. J., Cunningham, G., … Kofinas, P. (2015). Simple and inexpensive quantification of ammonia in whole blood. Molecular Genetics and Metabolism, 115(2-3), 95-100. doi:10.1016/j.ymgme.2015.04.004Prieto-Blanco, M. C., Jornet-Martinez, N., Verdú-Andrés, J., Molíns-Legua, C., & Campíns-Falcó, P. (2019). Quantifying both ammonium and proline in wines and beer by using a PDMS composite for sensoring. Talanta, 198, 371-376. doi:10.1016/j.talanta.2019.02.001Prieto-Blanco, M. C., Jornet-Martínez, N., Moliner-Martínez, Y., Molins-Legua, C., Herráez-Hernández, R., Verdú Andrés, J., & Campins-Falcó, P. (2015). Development of a polydimethylsiloxane–thymol/nitroprusside composite based sensor involving thymol derivatization for ammonium monitoring in water samples. Science of The Total Environment, 503-504, 105-112. doi:10.1016/j.scitotenv.2014.07.077Prieto-Blanco, M. C., Ballester-Caudet, A., Souto-Varela, F. J., López-Mahía, P., & Campíns-Falcó, P. (2020). Rapid evaluation of ammonium in different rain events minimizing needed volume by a cost-effective and sustainable PDMS supported solid sensor. Environmental Pollution, 265, 114911. doi:10.1016/j.envpol.2020.114911McEnaney, J. M., Blair, S. J., Nielander, A. C., Schwalbe, J. A., Koshy, D. M., Cargnello, M., & Jaramillo, T. F. (2020). Electrolyte Engineering for Efficient Electrochemical Nitrate Reduction to Ammonia on a Titanium Electrode. ACS Sustainable Chemistry & Engineering, 8(7), 2672-2681. doi:10.1021/acssuschemeng.9b05983Schiffer, Z. J., Lazouski, N., Corbin, N., & Manthiram, K. (2019). Nature of the First Electron Transfer in Electrochemical Ammonia Activation in a Nonaqueous Medium. The Journal of Physical Chemistry C, 123(15), 9713-9720. doi:10.1021/acs.jpcc.9b00669Moliner-Martínez, Y., Herráez-Hernández, R., & Campíns-Falcó, P. (2005). Improved detection limit for ammonium/ammonia achieved by Berthelot’s reaction by use of solid-phase extraction coupled to diffuse reflectance spectroscopy. Analytica Chimica Acta, 534(2), 327-334. doi:10.1016/j.aca.2004.11.044López Pasquali, C. E., Fernández Hernando, P., & Durand Alegría, J. S. (2007). Spectrophotometric simultaneous determination of nitrite, nitrate and ammonium in soils by flow injection analysis. Analytica Chimica Acta, 600(1-2), 177-182. doi:10.1016/j.aca.2007.03.015Kashima, H., & Regan, J. M. (2015). Facultative Nitrate Reduction by Electrode-Respiring Geobacter metallireducens Biofilms as a Competitive Reaction to Electrode Reduction in a Bioelectrochemical System. Environmental Science & Technology, 49(5), 3195-3202. doi:10.1021/es504882fCaballo-López, A., & Luque de Castro, M. D. (2006). Continuous Ultrasound-Assisted Extraction Coupled to Flow Injection−Pervaporation, Derivatization, and Spectrophotometric Detection for the Determination of Ammonia in Cigarettes. Analytical Chemistry, 78(7), 2297-2301. doi:10.1021/ac051115uBietz, J. A. (1974). Micro-Kjeldahl analysis by an improved automated ammonia determination following manual digestion. Analytical Chemistry, 46(11), 1617-1618. doi:10.1021/ac60347a040Lazouski, N., Schiffer, Z. J., Williams, K., & Manthiram, K. (2019). Understanding Continuous Lithium-Mediated Electrochemical Nitrogen Reduction. Joule, 3(4), 1127-1139. doi:10.1016/j.joule.2019.02.003McEnaney, J. M., Singh, A. R., Schwalbe, J. A., Kibsgaard, J., Lin, J. C., Cargnello, M., … Nørskov, J. K. (2017). Ammonia synthesis from N2and H2O using a lithium cycling electrification strategy at atmospheric pressure. Energy & Environmental Science, 10(7), 1621-1630. doi:10.1039/c7ee01126aCerdà, A., Oms, M. T., Forteza, R., & Cerdà, V. (1995). Evaluation of flow injection methods for ammonium determination in wastewater samples. Analytica Chimica Acta, 311(2), 165-173. doi:10.1016/0003-2670(95)00182-yMolins-Legua, C., Meseguer-Lloret, S., Moliner-Martinez, Y., & Campíns-Falcó, P. (2006). A guide for selecting the most appropriate method for ammonium determination in water analysis. TrAC Trends in Analytical Chemistry, 25(3), 282-290. doi:10.1016/j.trac.2005.12.002Verdouw, H., Van Echteld, C. J. A., & Dekkers, E. M. J. (1978). Ammonia determination based on indophenol formation with sodium salicylate. Water Research, 12(6), 399-402. doi:10.1016/0043-1354(78)90107-0Kempers, A. J., & Kok, C. J. (1989). Re-examination of the determination of ammonium as the indophenol blue complex using salicylate. Analytica Chimica Acta, 221, 147-155. doi:10.1016/s0003-2670(00)81948-0Yu, H., Yang, L., Li, D., & Chen, Y. (2021). A hybrid intelligent soft computing method for ammonia nitrogen prediction in aquaculture. Information Processing in Agriculture, 8(1), 64-74. doi:10.1016/j.inpa.2020.04.002Wang, C., Li, Z., Pan, Z., & Li, D. (2018). Development and characterization of a highly sensitive fluorometric transducer for ultra low aqueous ammonia nitrogen measurements in aquaculture. Computers and Electronics in Agriculture, 150, 364-373. doi:10.1016/j.compag.2018.05.011Fernandez, C. A., Hortance, N. M., Liu, Y.-H., Lim, J., Hatzell, K. B., & Hatzell, M. C. (2020). Opportunities for intermediate temperature renewable ammonia electrosynthesis. Journal of Materials Chemistry A, 8(31), 15591-15606. doi:10.1039/d0ta03753bGuo, J., & Chen, P. (2017). Catalyst: NH3 as an Energy Carrier. Chem, 3(5), 709-712. doi:10.1016/j.chempr.2017.10.004Sclafani, A., Augugliaro, V., & Schiavello, M. (1983). Dinitrogen Electrochemical Reduction to Ammonia over Iron Cathode in Aqueous Medium. Journal of The Electrochemical Society, 130(3), 734-736. doi:10.1149/1.2119794Zhou, F., Azofra, L. M., Ali, M., Kar, M., Simonov, A. N., McDonnell-Worth, C., … MacFarlane, D. R. (2017). Electro-synthesis of ammonia from nitrogen at ambient temperature and pressure in ionic liquids. Energy & Environmental Science, 10(12), 2516-2520. doi:10.1039/c7ee02716hMcdonald, M., Fuller, J., Fortunelli, A., Goddard, W. A., & An, Q. (2019). Highly Efficient Ni-Doped Iron Catalyst for Ammonia Synthesis from Quantum-Mechanics-Based Hierarchical High-Throughput Catalyst Screening. The Journal of Physical Chemistry C, 123(28), 17375-17383. doi:10.1021/acs.jpcc.9b04386Chen, S., Perathoner, S., Ampelli, C., Mebrahtu, C., Su, D., & Centi, G. (2017). Electrocatalytic Synthesis of Ammonia at Room Temperature and Atmospheric Pressure from Water and Nitrogen on a Carbon-Nanotube-Based Electrocatalyst. Angewandte Chemie International Edition, 56(10), 2699-2703. doi:10.1002/anie.201609533Wang, H.-B., Wang, J.-Q., Zhang, R., Cheng, C.-Q., Qiu, K.-W., Yang, Y., … Du, X.-W. (2020). Bionic Design of a Mo(IV)-Doped FeS2 Catalyst for Electroreduction of Dinitrogen to Ammonia. ACS Catalysis, 10(9), 4914-4921. doi:10.1021/acscatal.0c00271Bower, C. E., & Holm-Hansen, T. (1980). A Salicylate–Hypochlorite Method for Determining Ammonia in Seawater. Canadian Journal of Fisheries and Aquatic Sciences, 37(5), 794-798. doi:10.1139/f80-106Le, P. T. T., & Boyd, C. E. (2012). Comparison of Phenate and Salicylate Methods for Determination of Total Ammonia Nitrogen in Freshwater and Saline Water. Journal of the World Aquaculture Society, 43(6), 885-889. doi:10.1111/j.1749-7345.2012.00616.xPym, R. V. E., & Milham, P. J. (1976). Selectivity of reaction among chlorine, ammonia, and salicylate for determination of ammonia. Analytical Chemistry, 48(9), 1413-1415. doi:10.1021/ac50003a035Krom, M. D. (1980). Spectrophotometric determination of ammonia: a study of a modified Berthelot reaction using salicylate and dichloroisocyanurate. The Analyst, 105(1249), 305. doi:10.1039/an9800500305Viollier, E., Inglett, P. ., Hunter, K., Roychoudhury, A. ., & Van Cappellen, P. (2000). The ferrozine method revisited: Fe(II)/Fe(III) determination in natural waters. Applied Geochemistry, 15(6), 785-790. doi:10.1016/s0883-2927(99)00097-9Yegorov, D. Y., Kozlov, A. V., Azizova, O. A., & Vladimirov, Y. A. (1993). Simultaneous determination of Fe(III) and Fe(II) in water solutions and tissue homogenates using desferal and 1,10-phenanthroline. Free Radical Biology and Medicine, 15(6), 565-574. doi:10.1016/0891-5849(93)90158-qBAG, H., TÜRKER, A. R., TUNÇELI, A., & LALE, M. (2001). Determination of Fe(II)and Fe(III)in Water by Flame Atomic Absorption Spectrophotometry after Their Separation with Aspergillus niger Immobilized on Sepiolite. Analytical Sciences, 17(7), 901-904. doi:10.2116/analsci.17.901Kaasalainen, H., Stefánsson, A., & Druschel, G. K. (2016). Determination of Fe(II), Fe(III) and Fetotal in thermal water by ion chromatography spectrophotometry (IC-Vis). International Journal of Environmental Analytical Chemistry, 96(11), 1074-1090. doi:10.1080/03067319.2016.1232717Pu, X., Hu, B., Jiang, Z., & Huang, C. (2005). Speciation of dissolved iron(ii) and iron(iii) in environmental water samples by gallic acid-modified nanometer-sized alumina micro-column separation and ICP-MS determination. The Analyst, 130(8), 1175. doi:10.1039/b502548

Methods for nitrogen activation by reduction and oxidation

The industrial Haber-Bosch process to produce ammonia (NH3) from dinitrogen (N2) is crucial for modern society. However, N2 activation is inherently challenging and the Haber-Bosch process has significant drawbacks, as it is highly energy intensive, not sustainable due to substantial CO2 emissions primarily from the generation of H2 and requires large-centralized facilities. New strategies of sustainable N2 activation, such as low-temperature thermochemical catalysis and (photo)electrocatalysis, have been pursued, but progress has been hindered by the lack of rigor and reproducibility in the collection and analysis of results. In this Primer, we provide a holistic step-by-step protocol, applicable to all nitrogen-transformation reactions, focused on verifying genuine N2 activation by accounting for all contamination sources. We compare state-of-the-art results from different catalytic reactions following the protocol’s framework, and discuss necessary reporting metrics and ways to interpret both experimental and density functional theory results. This Primer covers various common pitfalls in the field, best practices to improve reproducibility and cost-efficient methods to carry out rigorous experimentation. The future of nitrogen catalysis will require an increase in rigorous experimentation and standardization to prevent false positives from appearing in the literature, which can enable advancing towards practical technologies for the activation of N2

Water electrolysis: from textbook knowledge to the latest scientific strategies and industrial developments

International audienceReplacing fossil fuels with energy sources and carriers that are sustainable, environmentally benign, and affordable is amongst the most pressing challenges for future socio-economic development. To that goal, hydrogen is presumed to be the most promising energy carrier. Electrocatalytic water splitting, if driven by green electricity, would provide hydrogen with minimal CO2 footprint. The viability of water electrolysis still hinges on the availability of durable earth-abundant electrocatalyst materials and the overall process efficiency. This review spans from the fundamentals of electrocatalytically initiated water splitting to the very latest scientific findings from university and institutional research, also covering specifications and special features of the current industrial processes and those processes currently being tested in large-scale applications. Recently developed strategies are described for the optimisation and discovery of active and durable materials for electrodes that ever-increasingly harness first-principles calculations and machine learning. In addition, a technoeconomic analysis of water electrolysis is included that allows an assessment of the extent to which a large-scale implementation of water splitting can help to combat climate change. This review article is intended to cross-pollinate and strengthen efforts from fundamental understanding to technical implementation and to improve the ‘junctions’ between the field's physical chemists, materials scientists and engineers, as well as stimulate much-needed exchange among these groups on challenges encountered in the different domains

Use of CO as a cleaning tool of highly active surfaces in contact with ionic liquids. Ni deposition on Pt(111) surfaces in IL

This work proposes a pretreatment strategy of a flame-annealed Pt(111) single crystal ensuring surface ordering and avoiding surface contamination for experiments in ionic liquid (IL) media,. A room temperature ionic liquid (RTIL) and a Deep Eutectic Solvent (DES) representative of two families of ionic liquids were selected as test electrolytes: The RTIL used was the 1-ethyl-2,3-dimethylimidazolium bis(trifluoromethyl)sulfonylimide ([Emmim][Tf2N]) and the DES was based on the eutectic mixture of choline chloride (ChCl) and urea (1ChCl:2urea molar ratio). The electrode was flame-annealed and cooled down in CO atmosphere until the surface was fully covered by a protective carbon monoxide (CO) layer. Prior to experiments, the removal of CO from the surface was performed by electrochemical oxidation. The CO reactivity on Pt(111) was different depending on the IL nature. While CO is oxidised easily to CO2 in [Emmim][Tf2N], in DES CO remains adsorbed on the substrate and restructures undergoing an order-disorder transition. For both liquids, the proposed method allows obtaining neat blank cyclic voltammograms, demonstrating that the adsorption of CO is a useful tool to protect the high catalytic surfaces such as Pt in contact with ILs. To illustrate the feasibility of the CO treatment in electrochemical work with ILs, the general trends for the modification of Pt(111) single crystal surface with metallic nickel nanostructures on both types of IL was investigated. Nickel electrodeposition on Pt(111) surface was explored in both [Emmim][Tf2N] and DES by using classical electrochemical techniques such as cyclic voltammetry and chronoamperometry, and the deposits were characterized by FE-SEM ,EDS and XPS

Reactivity with Water and Bulk Ruthenium Redox of Lithium Ruthenate in Basic Solutions

The reactivity of water with Li rich layered Li2RuO3 and partial exchange of Li2O with H2O within the structure has been studied under aqueous electro chemical conditions. Upon slow delithiation in water over long time periods, micron size Li2RuO3 particles structurally transform from an O3 structure to an O1 structure with a corresponding loss of 1.25 Li ions per formula unit. The O1 stacking of the honeycomb Ru layers is imaged using high resolution HAADF STEM, and the resulting structure is solved from X ray powder diffraction and electron diffraction. In situ X ray absorption spectroscopy suggests that reversible oxidation reduction of bulk Ru sites is realized on potential cycling between 0.4 VRHE and 1.25 VRHE in basic solutions. In addition to surface redox pseudocapacitance, the partially delithiated phase of Li2RuO3 shows high capacity which can be attributed to bulk Ru redox in the structure. This work demonstrates that the interaction of aqueous electrolytes with Li rich layered oxides, can result in the formation of new phases with electro chemical properties that are distinct from the parent material. This understanding is important for the design of aqueous batteries, electrochemical capacitors and chemically stable cathode materials for Li ion batterie

Towards Intelligent Crowd Behavior Understanding through the STFD Descriptor Exploration

Realizing the automated and online detection of crowd anomalies from surveillance CCTVs is a research-intensive and application-demanding task. This research proposes a novel technique for detecting crowd abnormalities through analyzing the spatial and temporal features of input video signals. This integrated solution defines an image descriptor (named spatio-temporal feature descriptor - STFD) that reflects the global motion information of crowds over time. A CNN has then been adopted to classify dominant or large-scale crowd abnormal behaviors. The work reported has focused on: 1) detecting moving objects in online (or near real-time) manner through spatio-temporal segmentations of crowds that is defined by the similarity of group trajectory structures in temporal space and the foreground blocks based on Gaussian Mixture Model (GMM) in spatial space; 2) dividing multiple clustered groups based on the spectral clustering method by considering image pixels from spatio-temporal segmentation regions as dynamic particles; 3) generating the STFD descriptor instances by calculating the attributes (i.e., collectiveness, stability, conflict and crowd density) of particles in the corresponding groups; 4) inputting generated STFD descriptor instances into the devised convolutional neural network (CNN) to detect suspicious crowd behaviors. The test and evaluation of the devised models and techniques have selected the PETS database as the primary experimental data sets. Results against benchmarking models and systems have shown promising advancements of this novel approach in terms of accuracy and efficiency for detecting crowd anomalies

Towards Intelligent Crowd Behavior Understanding through the STFD Descriptor Exploration

Realizing the automated and online detection of crowd anomalies from surveillance CCTVs is a research-intensive and application-demanding task. This research proposes a novel technique for detecting crowd abnormalities through analyzing the spatial and temporal features of input video signals. This integrated solution defines an image descriptor (named spatio-temporal feature descriptor - STFD) that reflects the global motion information of crowds over time. A CNN has then been adopted to classify dominant or large-scale crowd abnormal behaviors. The work reported has focused on: 1) detecting moving objects in online (or near real-time) manner through spatio-temporal segmentations of crowds that is defined by the similarity of group trajectory structures in temporal space and the foreground blocks based on Gaussian Mixture Model (GMM) in spatial space; 2) dividing multiple clustered groups based on the spectral clustering method by considering image pixels from spatio-temporal segmentation regions as dynamic particles; 3) generating the STFD descriptor instances by calculating the attributes (i.e., collectiveness, stability, conflict and crowd density) of particles in the corresponding groups; 4) inputting generated STFD descriptor instances into the devised convolutional neural network (CNN) to detect suspicious crowd behaviors. The test and evaluation of the devised models and techniques have selected the PETS database as the primary experimental data sets. Results against benchmarking models and systems have shown promising advancements of this novel approach in terms of accuracy and efficiency for detecting crowd anomalies