Electrochimica ActaPub Date : 2024-11-16DOI: 10.1016/j.electacta.2024.145363
Rok Šmerc, Damijan Miklavčič, Samo Mahnič-Kalamiza
{"title":"AN EXPERIMENTALLY VALIDATED NUMERICAL MODEL OF PH CHANGES IN SURROGATE TISSUE INDUCED BY ELECTROPORATION PULSES","authors":"Rok Šmerc, Damijan Miklavčič, Samo Mahnič-Kalamiza","doi":"10.1016/j.electacta.2024.145363","DOIUrl":"https://doi.org/10.1016/j.electacta.2024.145363","url":null,"abstract":"Electroporation often leads to electrochemical reactions at the electrode-electrolytic solution interface, particularly when using monophasic pulses of considerable duration (typically on the order of several microseconds or longer) that cause not only capacitive charging of the double-layer, but also faradaic charge transfer between the electrodes and the solution. Applications, where the electrochemical changes are to be either avoided or actively exploited to benefit the treatment, range from gene electrotransfer to electrolytic ablation of tissue. Through numerical modelling and experimental validation, our study explores the extent of pH changes induced by faradaic currents in a surrogate tissue. A mechanistic multiphysics model of pH changes was developed based on first principles, incorporating hydrolysis reactions at the anode and cathode, and the Nernst-Planck model of ion transport. The model was validated using agarose gel tissue phantoms designed to simulate unbuffered and buffered (mimicking <em>in vivo</em> tissue buffering capacity) conditions. An imaging system with pH-sensitive dyes was developed and used to visualise and quantify pH front formation and migration. The model predictions qualitatively aligned well with experimental data, differentiating pH front behaviour between unbuffered and buffered media. However, the quantitative accuracy in predicting the temporal and spatial evolution of the pH fronts can be further improved. Experimental observations emphasise the need for more advanced models. Nevertheless, the developed model provides a sound theoretical foundation for predicting pH changes due to high-voltage electric pulse delivery, such as encountered in electroporation-based treatments and therapies.","PeriodicalId":305,"journal":{"name":"Electrochimica Acta","volume":"247 1","pages":""},"PeriodicalIF":6.6,"publicationDate":"2024-11-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142642670","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Electrochimica ActaPub Date : 2024-11-16DOI: 10.1016/j.electacta.2024.145340
Fiyanshu Kaka, Kalyan Sundar Krishna Chivukula
{"title":"Deciphering the influence of multi-component blends and their electronic band structure on the performance of All-Solid-State Batteries","authors":"Fiyanshu Kaka, Kalyan Sundar Krishna Chivukula","doi":"10.1016/j.electacta.2024.145340","DOIUrl":"https://doi.org/10.1016/j.electacta.2024.145340","url":null,"abstract":"The emergence of all-solid-state batteries (ASSBs) introduces a paradigm shift in energy storage technology, offering enhanced safety compared to conventional liquid-based metal-ion batteries. Significant effort is directed toward optimizing the solid-electrolyte blend composition to enhance the battery’s electrochemical performance. Despite some promising results, a lack of guidelines persists, particularly for optimizing multicomponent solid electrolytes given their large parameter window. This study aims to address this challenge by implementing a unified diffuse-interface approach to model and simulate the solid electrolyte morphologies and their corresponding electrochemical performance when incorporated in a battery. The electrolyte microstructures are simulated using the Cahn-Hilliard formulation while a diffuse-interface framework formulated in terms of electrochemical potential is utilized for exploring Li-ion transport across the battery. It is found that, while the variegated microstructures arising from various solid electrolyte blend compositions influence the power density of the battery, the electronic band structure of the blend phases is an important consideration. The proposed model is versatile and can be adapted for various battery technologies beyond ASSBs. This expands its potential impact and could lead to innovations in energy storage technology.","PeriodicalId":305,"journal":{"name":"Electrochimica Acta","volume":"64 1","pages":""},"PeriodicalIF":6.6,"publicationDate":"2024-11-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142642667","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Low-Loaded Catalyst Layers For Proton Exchange Membrane Fuel Cell Dynamic Operation Part 1: Experimental Study","authors":"Florent Vandenberghe, Fabrice Micoud, Pascal Schott, Arnaud Morin, Clémence Lafforgue, Marian Chatenet","doi":"10.1016/j.electacta.2024.145364","DOIUrl":"https://doi.org/10.1016/j.electacta.2024.145364","url":null,"abstract":"In the past decades, the proton exchange membrane fuel cell (PEMFC) components, cell/stack designs and system architecture have been significantly improved. However, despite great initial performance, PEMFC systems still suffer technological limitations, such as their initial cost, partly due to the use of expensive Pt-based electrocatalyst, which prevents widespread industrial deployment. Lowering the cathode catalyst loading while keeping high (and durable) catalytic activity has been intensively studied. In this work, low-loaded catalyst layers (20 and 100 µg<sub>Pt</sub> cm<sub>geo</sub><sup>−2</sup>) are tested in PEMFC differential single-cell (DC) under high reactant stoichiometry to characterize their intrinsic electrochemical properties under various ideal and well-controlled operating conditions of cell temperature (<em>T</em>) and relative humidity (<em>RH</em>). Particularly, the change of the membrane hydration state, via the ohmic resistance measurement, and the Pt-oxides surface coverage are investigated to gather information on the physico-chemical and electrochemical mechanisms involved in the cathode active layer, and the typical performance hysteresis observed during dynamic operation such as polarization curves. These specific electrochemical measurements further enable to build a dataset, that can be used to improve PEMFC models taking into account the complex ORR mechanism, and the role of the Pt oxides in catalyst layer transient operation and degradation.","PeriodicalId":305,"journal":{"name":"Electrochimica Acta","volume":"1 1","pages":""},"PeriodicalIF":6.6,"publicationDate":"2024-11-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142642666","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Enhanced Long-Term Stability of Zinc-Air Batteries Using a Quaternized PVA-Chitosan Composite Separator with Thin-Layered MoS2","authors":"Nuttapon Suppanucroa, Warunyoo Yoopensuk, Jirapha Pimoei, Wacharapisuth Thanapong-a-morn, Wathanyu Kao-Ian, Phakkhananan Pakawanit, Falko Mahlendorf, Soorathep Kheawhom, Anongnat Somwangthanaroj","doi":"10.1016/j.electacta.2024.145361","DOIUrl":"https://doi.org/10.1016/j.electacta.2024.145361","url":null,"abstract":"Due to their high energy density and cost-effectiveness, rechargeable zinc-air batteries (ZABs) are increasingly recognized for their potential as long-duration energy storage solutions. A crucial component for maximizing their efficiency is the membrane separator, which must exhibit high hydroxide-ion conductivity and long-term stability. This study introduces an innovative hybrid composite separator, created by embedding thin-layered molybdenum disulfide (MoS<sub>2</sub>), known for its intrinsic negative charge, into a polycationic quaternized PVA-chitosan (CS) matrix. Polyvinyl alcohol (PVA) is functionalized with quaternary ammonium (QA) groups before being combined with CS and MoS<sub>2</sub>, using a solvent blending technique. The separator's three-dimensional structure and morphology is analyzed via synchrotron radiation X-ray tomographic microscopy (SR-XTM). Results demonstrate that the ZAB equipped with a quaternized PVA/CS/0.5 wt.% MoS<sub>2</sub> composite separator achieved a high conductivity of 87.3 mS cm<sup>-1</sup> and exceptional stability, enduring over 465 cycles. This performance is attributed to the synergistic interaction between the quaternized PVA-CS matrix and the MoS<sub>2</sub> surface, forming robust polymer complexes through electrostatic interactions. These findings suggest that the developed separators hold significant promise for advanced ZAB applications.","PeriodicalId":305,"journal":{"name":"Electrochimica Acta","volume":"13 1","pages":""},"PeriodicalIF":6.6,"publicationDate":"2024-11-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142637832","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Electrochimica ActaPub Date : 2024-11-15DOI: 10.1016/j.electacta.2024.145333
Lei Zhang, Bing Sun, Qinghua Liu, Lin Song, Teibang Zhang, Xiaobo Duan
{"title":"Corrigendum to the author information of “Solvent-derived inorganic F and N-rich solid electrolyte interface for stable lithium metal batteries” [Electrochimica Acta, Volume 503, 2024, 144909]","authors":"Lei Zhang, Bing Sun, Qinghua Liu, Lin Song, Teibang Zhang, Xiaobo Duan","doi":"10.1016/j.electacta.2024.145333","DOIUrl":"https://doi.org/10.1016/j.electacta.2024.145333","url":null,"abstract":"It has come to our attention that we misspelled the name of the corresponding author,","PeriodicalId":305,"journal":{"name":"Electrochimica Acta","volume":"18 1","pages":""},"PeriodicalIF":6.6,"publicationDate":"2024-11-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142637646","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Electrochimica ActaPub Date : 2024-11-15DOI: 10.1016/j.electacta.2024.145360
Mirjam Rogler, Richard Wagner, Simon Thiele, Michel Suermann
{"title":"Guidance for targeted degradation analysis of OER kinetics of low-loading iridium-based catalysts in PEM water electrolysis cells","authors":"Mirjam Rogler, Richard Wagner, Simon Thiele, Michel Suermann","doi":"10.1016/j.electacta.2024.145360","DOIUrl":"https://doi.org/10.1016/j.electacta.2024.145360","url":null,"abstract":"This paper critically evaluates three methods for determining metrics of the oxygen evolution reaction (OER) describing the performance and stability of low-loading iridium-based anode catalyst layers (CLs) in proton exchange membrane water electrolysis (PEMWE) cells. The methods applied are OER mass activity, voltage breakdown analysis (VBA), and constant Tafel slope VBA (CT-VBA). They are used to assess the OER metrics as a function of anode CL configurations, potential cycling, and level of degradation. Therefore, various accelerated stress tests (ASTs) are carried out for a targeted degradation of different anode CLs based on Ir black or Ir oxide. It turns out that the OER mass activity method is robust, straightforward and an ideal method for e.g., in-house screening tasks. On the other hand, the VBA method is suitable for comparative analysis across laboratories by distinguishing between the three main overpotentials. The CT-VBA method, however, offers improved accuracy, as it accounts for mass transport overpotential at low current density, and is particularly suitable for determining apparent exchange current density values further used in modelling approaches. This benefit comes with a drawback, as commonly accepted reference Tafel slopes for respective catalyst type and PTL configurations would be required within the PEMWE community. This guidance therefore helps to choose the right method for determining OER metrics depending on the research question.","PeriodicalId":305,"journal":{"name":"Electrochimica Acta","volume":"25 1","pages":""},"PeriodicalIF":6.6,"publicationDate":"2024-11-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142637833","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Electrochimica ActaPub Date : 2024-11-15DOI: 10.1016/j.electacta.2024.145347
Zhi Liu , Ningning Chen , Wanying Guo , Yinshuang Pang , Nailu Shen , Hong Chen , Wanying Zhang , Feichang Feng , Jingxiang Zhao , Yanyu Liang
{"title":"Facile sulfur chemistry assisted carbon reconfiguration for efficient potassium ion electrochemical storage","authors":"Zhi Liu , Ningning Chen , Wanying Guo , Yinshuang Pang , Nailu Shen , Hong Chen , Wanying Zhang , Feichang Feng , Jingxiang Zhao , Yanyu Liang","doi":"10.1016/j.electacta.2024.145347","DOIUrl":"10.1016/j.electacta.2024.145347","url":null,"abstract":"<div><div>Carbon-based materials are commonly used as anodes for potassium-ion batteries due to their high conductivity and stable cycling performance. However, their practical application is greatly hindered by their low capacity. Herein, we introduce facile sulfur chemistry including thioether bonds and CoS₂ into a nitrogen-oxygen co-doped partially graphitized carbon skeleton (NOGC), while the extra reconfiguration process of carbon assists forming the CoS₂@R-NOGC composites. The reconfigured NOGC (R-NOGC), enriched with highly electronegative elements (N, O, S), significantly enhances the reversible potassium ion storage capacity. The ordered carbon structure provides more efficient ionic transport pathways, thereby improving K⁺ transport efficiency. Moreover, layered CoS₂ acts as additional ion transport channels and active sites, further enhancing ion mobility and storage capacity. R-NOGC also promotes the reconstruction and repair of the solid electrolyte interface (SEI) layer to form a more robust interface. As a result of the synergistic effect between R-NOGC and CoS₂, it exhibits excellent anode performance, including a high reversible capacity (314.0 mAh/g at 0.1 A/g) and long-term stability (250.3 mAh/g at 0.5 A/g after 1,000 cycles). This work presents a novel strategy for designing and synthesizing high-performance anode materials for potassium-ion batteries, significantly enhancing both capacity and cycling stability.</div></div>","PeriodicalId":305,"journal":{"name":"Electrochimica Acta","volume":"509 ","pages":"Article 145347"},"PeriodicalIF":5.5,"publicationDate":"2024-11-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142637647","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Electrochimica ActaPub Date : 2024-11-15DOI: 10.1016/j.electacta.2024.145359
José A. Tamayo, Carolina Ramírez-Sánchez, Jorge A. Calderón
{"title":"Effect of ammoniacal thiosulfate solution composition on the gold dissolution rate: An electrochemical study","authors":"José A. Tamayo, Carolina Ramírez-Sánchez, Jorge A. Calderón","doi":"10.1016/j.electacta.2024.145359","DOIUrl":"https://doi.org/10.1016/j.electacta.2024.145359","url":null,"abstract":"The electrochemical behavior of ammoniacal thiosulfate solutions (S<sub>2</sub>O<sub>3</sub><sup>2-</sup>- NH3-Cu<sup>2+</sup> -EDTA) has been studied for varying electrolyte compositions in the gold electro-dissolution. A gold rotating disk electrode (RDE) was employed to measure anodic and cathodic polarization curves in alkaline thiosulfate solutions. Potentiodynamic polarization showed how thiosulfate, ammonia, and copper concentration influence the cathodic and anodic behavior of the electrolyte. Likewise, the influence of oxygen on the electrochemical behavior system was evidenced from the analysis of polarization curves, and using Koutecky – Levich equation (slope of 59.60 mV/decade), it was possible to determine the peroxide pathway for oxygen reduction reaction (ORR) with two-electron transference. Additionally, gold dissolution and thiosulfate degradation were evaluated using the gold foil leaching tests. It was found solutions with a 0.2 mol L<sup>-1</sup> thiosulfate concentration favored the dissolution of gold and by maintaining an adequate ratio between thiosulfate/ammonium (1:3) or thiosulfate/copper (4:1) enable the attainment high gold dissolution and lower degradation of thiosulfate.","PeriodicalId":305,"journal":{"name":"Electrochimica Acta","volume":"38 1","pages":""},"PeriodicalIF":6.6,"publicationDate":"2024-11-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142637831","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Electrochimica ActaPub Date : 2024-11-14DOI: 10.1016/j.electacta.2024.145357
Megan C. Davis, Wilton J.M. Kort-Kamp, Edward F. Holby, Piotr Zelenay, Ivana Matanovic
{"title":"Computational Screening of Transition Metal-Nitrogen-Carbon Materials as Electrocatalysts for CO2 Reduction","authors":"Megan C. Davis, Wilton J.M. Kort-Kamp, Edward F. Holby, Piotr Zelenay, Ivana Matanovic","doi":"10.1016/j.electacta.2024.145357","DOIUrl":"https://doi.org/10.1016/j.electacta.2024.145357","url":null,"abstract":"Atomically dispersed M-N-C catalysts are a promising, cost-effective class of materials for reducing CO<sub>2</sub> to value-added products through the CO<sub>2</sub> reduction reaction (CO<sub>2</sub>RR). However, complex multi-objective optimization of several properties including catalyst stability, activity, and selectivity for target products are necessary to make CO<sub>2</sub>RR more efficient with this class of catalysts. We systematically investigate activity and selectivity for carbon monoxide, formic acid, and hydrogen evolution pathways on model M-N<sub>4</sub>C<sub>10</sub> active sites for 26 transition metal species. Our work shows that under acidic conditions, all the considered M-N<sub>4</sub>C<sub>10</sub> sites except M=Fe, Co, Cr, Cd, and Pt should have CO<sub>2</sub>RR onset potentials lower than the hydrogen evolution reaction. We identify the transition metal active sites that should catalyze the CO pathway, leading to gaseous CO production, CO poisoning, or reduction to further products. To understand the reasons for predicted activity and selectivity, we furthermore correlate atomic features for the transition metals with the calculated onset potential of each pathway, showing moderate correlation between both electronegativity and atomic radii with the CO<sub>2</sub>RR onset potentials. The high-throughput and feature-based approach in this work not only serves as a guide for present experimental efforts but can also serve as a starting point for machine learning efforts to accelerate active site modeling and catalyst discovery.","PeriodicalId":305,"journal":{"name":"Electrochimica Acta","volume":"163 1","pages":""},"PeriodicalIF":6.6,"publicationDate":"2024-11-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142610086","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Electrochimica ActaPub Date : 2024-11-14DOI: 10.1016/j.electacta.2024.145351
Shi Li, Maokai Yin, Pirong Shi, Xiangnan Wang, Peng Qiu, Jie Wu, Ye Han
{"title":"Effect of Sr2+ doping on the structure and electrical properties of hexagonal perovskite Ba7-xSrxNb4MoO20-δ electrolyte: experimental and DFT modeling studies","authors":"Shi Li, Maokai Yin, Pirong Shi, Xiangnan Wang, Peng Qiu, Jie Wu, Ye Han","doi":"10.1016/j.electacta.2024.145351","DOIUrl":"https://doi.org/10.1016/j.electacta.2024.145351","url":null,"abstract":"Ba<sub>7</sub>Nb<sub>4</sub>MoO<sub>20</sub> exhibits excellent oxygen ion transport properties and is a promising electrolyte material for solid oxide fuel cell (SOFC). To further enhance its oxygen ionic conductivity, element doping is an effective strategy. However, few studies have delved into the impact mechanism of doping strategies on the electrolyte's conductivity properties from the perspective of electronic structure. Here, the enhancement mechanism of oxygen ionic conductivity in Ba<sub>7</sub>Nb<sub>4</sub>MoO<sub>20</sub> was analyzed using the the methods of density of states (DOS) and Crystal Orbital Hamilton Populations (COHP). Since the electronic conductivities of the electrolytes are negligible, their total conductivies can essentially be regarded as the conductivies of oxygen ions. As the Sr doping amount increases, the oxygen ionic conductivities of the electrolytes also increase. The bulk conductivity shows a negative correlation with the Sr doping amount, which is due to the higher bond energy of Sr-O compared to Ba-O. On the other hand, Sr promotes grain growth and reduces the number of grain boundaries, thereby decreasing the resistance to oxygen diffusion at the grain boundaries and thus enhancing the grain boundary conductivity. In the Ba<sub>7-</sub><em><sub>x</sub></em>Sr<em><sub>x</sub></em>Nb<sub>4</sub>MoO<sub>20-δ</sub> (<em>x</em>=0, 0.1, 0.2, 0.3, and 0.4) perovskite oxides, Ba<sub>6.6</sub>Sr<sub>0.4</sub>Nb<sub>4</sub>MoO<sub>20-δ</sub> has the highest conductivity, reaching 1.12 × 10<sup>-4</sup>S cm<sup>-1</sup> at 500°C. This work not only develops a SOFC electrolyte material with promising application prospects, but also provides theoretical guidance for its doping modification.","PeriodicalId":305,"journal":{"name":"Electrochimica Acta","volume":"38 1","pages":""},"PeriodicalIF":6.6,"publicationDate":"2024-11-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142610087","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}