Electrochemical Impedance Spectroscopy Study

Electrochemical Impedance Spectroscopy Study Electrochemical impedance spectroscopy An EIS study was carried out at different dc potentials in order to study the mechanism of ORR in O2 saturated alkaline solutions on prepared GDEs. The Nyquist plots of GDEs under different polarization potentials are shown in Fig. 5. The impedance diagrams show two different behaviors which depend on the applied dc potentials. In the other words, the shape of plots changed at different potentials, suggesting different electrochemical processes occurring on the electrode. The impedance spectra acquired at the potential lower than 0.7 V show one loop in the high frequency region associated with the time constant of a charge transfer process and semi-infinite diffusive manner related to Warburg component in the low frequency region. This semi-infinite diffusive character is related to the adsorption of reactants and intermediate products. The Nyquist plots of O2 reduction on GDEs at the E≠¥0.7 show two loops. The processes that could be involved on the electrode surface that would produce these changes include [37]: (1) Diffusion of O2 through the gas phase in the pores (of porous carbon supported catalyst) and the electrolyte to the reaction site. (2) Adsorption or heterogeneous surface reaction of the oxygen, together with oxygen diffusion. (3) Charge transfer. (4) Diffusion of reduction products into the bulk electrolyte Many reaction mechanisms have been proposed to describe ORR in aqueous electrolytes. Among these models, the Damjanovic model (Fig. 6) is one of the most extensively employed models, due to its applicability over a wide potential region. Damjanovic model describes the ORR as a multi-electron reaction which O2 molecules in the vicinity of the electrode are irreversibly reduced directly to H2O through 4-electron transfer (with a constant rate, k1) or to H2O2 through 2-electron transfer (constant rate, k2). The H2O2 formed can be reduced to H2O through 2-electron transfer (constant rate, k3) or diffuse into the bulk solution [38]. The ORR mechanism on transition metals has also been investigated by theoretical calculation based on the electronic structure [39-40]. The dissociative mechanism and the associative mechanism are proposed for a low current density range (more positive potentials) and a high current density range (more negative potentials), respectively [41]. Dissociative Mechanism (E≠¥0.7 V): In this mechanism, no H2O2 is produced. On a metal surface, O2 adsorption breaks the O-O bond and forms adsorbed atomic O, which further gains two electrons in the two consecutive steps, forming hydroxide ions. Since there is no adsorbed O2 on the catalyst surface, H2O2 cannot be formed. This mechanism can be considered a detailed form of the direct 4-electron pathway and can be written as follows: 1/2O2 + M(metal active sites) → O ºads (11) O ºads + e + H2O → OHads + OHaq (12) OHads + e → OHads → OHaq (13) Associative Mechanism (EË‚0.7 V): Since adsorbed O2 is present, the O-O bond may not be broken in the following steps, resulting in the formation of H2O2. The H2O2 could either be further reduced to H2O or be a final product. Therefore, the mechanism can be written as follows: O2,ads + 2H2O + 2e → H2O2 + 2OH (14) H2O2 + 2e → 2OH (15) The further reduction of H2O2(ads) to hydroxide ions occurs only once the enough overpotential has been reached and before the formed H2O2 diffuse into the bulk solution [41]. The two loop manner of GDEs in Nyquist plots may be related to two basic steps. On the other hand, for E ≠¥ 0.7 V, two time constants are detected during the impedance measurements (Fig. 5). The first time constant at high frequencies is associated with the charge transfer reaction according to Eq. 12, while the second may be associated with the further reduction of OHads to produce OH based Eq. 13. On the other hand, for EË‚0.7 V, the first time constant is related to H2O2 intermediate formation according to Eq. 14 and further semi-infinitive diffusive manner in the low frequency region can be explained by adsorption and diffusion of this intermediate into the bulk solution. In order to obtain quantitative information from impedance spectra in Fig. 5, two electric circuits were employed (Fig. 7). The electric circuit in Fig. 7a was used to simulate the impedance response of those spectra with OCP and E Using the equivalent circuits shown in Fig. 7, a constant phase element (CPE) is suggested instead of pure capacitance (C), due to the non-homogeneous surface of the electrodes. The impedance of CPE is defined as [Yo(jω)n]-1, where Yo is a constant with dimension (S.sn), while the exponent n denotes the correction factor pertaining to the roughness of the electrode and has values that range from 0 to 1. A pure capacitance yields n=1, a pure resistance yields n=0, while n=0.5 represents the ideal Warburg impedance. The true capacitance values can be calculated using the following equation [38]: C=[Yo Ãâ€" R (1-n)]1/n (14) According to equivalent circuits shown in Fig. 7, Rs is associated with the resistance of the solution, connectors, leads and wires. R1 is the charge transfer resistance of the reduction process from O2 to H2O2, R2 is the resistance of adsorbed species with H2O2 as the main intermediate or O2 adsorption into the GDE pores in the figure 7.a. The R1 and R2 circuit components in figure 7b are the charge transfer resistance of the reduction process of O ºads to OHads and the reduction process of OHads to OH, respectively. Parameters calculated from the equivalent circuits (Fig. 7) of O2 reduction on the GDEs are listed in Table 3. According to table 3, the Rs values change as a function of the potential, indicating that the contribution of the apparatus (connectors, leads and wires) from the total impedance of system shouldn’t be dismissed. So, the Rs values have a contribution function of both electrolyte and the apparatus resistance, i.e., connectors, leads and wires. R1 and R2 also show a dependence on the applied dc potentials (Fig. 8). By increasing the positive potential, the R1 values decrease. In the potential region of lower than 0.7 V, the adsorption of free O2 molecules happens on the metal catalyst and then O2,ads reduces to OHads (Eq.8). In the applied dc potential of E≠¥0.7 V, the adsorption of O ºads free radicals happens. By increasing the positive applied potentials, the adsorbed amount of O2,ads and O ºads increases and the further reduction process occurs more easily in the catalyst layer. So the R1 values will be decreased. The dependence of true capacitance values of the applied potentials is shown in Fig. 10. The adsorbed species enhancement by increasing the more positive potentials causes to decrease of C1 values. The R2 values for EË‚0.7 V are related to the adsorption of molecules like H2O2,ads into the GDE pores. When the potential is increased to more positive potentials, the adsorption of H2O2,ads spec ies by the oxygen atom orientation to the metal catalysts will be increased and R2 values became higher. In the potential region of E≠¥0.7 V, the OH,ads species which are reduced to OHaq, increase and charge transfer happens more easily. So the R2 values will be decreased. The C2 values also decrease because of more species adsorption (Fig. 10). Comparison of R values for GDEs shows that the Pt.Ru/C electrocatalyst has the lowest resistance in the whole range of applied dc potentials because of charge transferring occurring more easily and so ORR happens more rapidly at this electrocatalyst type. This behavior can be observed due to the synergistic effects of Pt and Ru catalyst species. The true capacitances of GDEs also show that the calculated of Pt.Ru/C and Ru/C electrocatalyst are higher than Pt.C ones. It is because the Ru species act as a protonic capacitor in the Pt.Ru/C and Ru/C GDEs. 3.5. Chronoamperometery The oxygen diffusion coefficients of GDEs were determined by chronoamperometry technique. Chronoamperograms were obtained by holding the potential of the electrodes at +1.2 V for 10 s and then holding it at +0.4 V relative to the Ag/AgCl electrode for 500 s with oxygen flowing along the electrolyte. With plotting i vs. t−1/2, the linear dependence relationship was obtained for different electrodes [42]: (16) Where I is the limited current, A the surface area of the electrode, D the diffusion coefficient, C the concentration of oxygen, n the number of electrons in the overall reaction of ORR, F the Faraday’s constant, t the time, and à ¯Ã‚ Ã‚ °Ãƒ ¯Ã¢â€š ¬Ã‚  is equal to 3.14. Fig. 11 shows the chronoamperograms of GDEs at +0.4V in relative to the Ag/AgCl in alkaline media. . Cottrell parameters are listed in Table 4, also. The results confirmed the higher Cottrell slope and D values for Pt.Ru/C electrode. So, the Pt.Ru/C cathode has more permeability and activity towards oxygen reduction reaction. Conclusion In this investigation, Pt/C, Ru/C and Pt.Ru/C bimetallic electrocatalysts were prepared by chemical reduction process. Then the resulted inks were coated on carbon paper and used as gas diffusion electrodes for oxygen reduction reaction in alkaline media. The surface structure of oxygen depolarized cathodes was studied by SEM and EDX analysis. The SEM results showed that all the cathodes consist of rough and porous structures. And Pt, Ru nanclusters were deposited quite uniformly onto/into Vulcan carbon supports with the average particle size of about 30-45 nm. The ORR activity of cathodes was evaluated in 0.1 M O2 saturated NaOH media. Comparison of cyclic voltamograms of Pt/C, Ru/C and Pt.Ru/C electrodes in O2 saturated solutions show that for Pt.Ru/C catalyst current increase induced by ORR is shifted towards more negative electrode potentials and only higher current values have been obtained within the ORR region. It can be concluded that the second metal addition has influenced the catalytic activity of electrocatalyst toward ORR. This matter can be related to synergistic effect, which is playing a critical role in ORR activity. The Pt.Ru/C cathodes showed lower Tafel slops and high current densities. An EIS study was carried out at different dc potentials in order to study the mechanism of ORR in O2 saturated alkalin e solutions on prepared GDEs. The Nyquist plots of GDEs under different polarization potentials show two different behaviors, suggesting different associative and dissociative electrochemical processes occurring on the electrode.

Workforce Diversity Definition

Workplace diversity is a people issue, focused on the differences and similarities that people bring to an organization. It is usually defined broadly to include dimensions beyond those specified legally in equal opportunity and affirmative action non-discrimination statutes. Diversity is often interpreted to include dimensions which influence the identities and perspectives that people bring, such as profession, education, parental status and geographic location.Benefits of workforce diversity. Best available talent.Older employees can bring experience and a strong work ethic to the university.Lecturers from other countries, often have an exceptional education, here or abroad, in science and more technical fields.Universities that provide equal opportunities to all workers can select, interview, screen and hire the most educated and experienced workers.More effective execution. Operate more effectively than less-diverse universities due to collective education and experience. Inspire their employees, lecturers and students to perform to the best of their ability.Experienced and educated people tend to be better at planning, time management, goal setting, work delegation and projects completed on time. Negative impacts of workforce diversity.Unresolved conflict.Lecturers and students that come from different cultural backgrounds have different perspectives on how to handle issues or concerns that arise. No parallel understandings between lecturers, students and workers prohi bit effective resolution of conflicts.Poor communication.Different countries and different native languages of students and lecturers prohibit clear and meaningful communication between them.Train the family of the university on cultural awareness and tolerance of differences to encourage them to openly discuss their different viewpoints on things as opposed to avoiding interaction or getting into conflict.Examples of workforce diversity in International Islamic University Malaysia.Lecturers. Many lecturers of IIUM come from different countries such as Russia, Japan, Uzbekistan, Bangladesh and so on. Workforce diversity allows IIUM to choose the IONbest lecturers to serve and educate their students.Students. Students of IIUM not only come from local citizens but also come from other countries such as Brunei Darussalam, Middle East countries and others. IIUM only selects the best students to be in this university. Workforce Diversity Definition Workplace diversity is a people issue, focused on the differences and similarities that people bring to an organization. It is usually defined broadly to include dimensions beyond those specified legally in equal opportunity and affirmative action non-discrimination statutes. Diversity is often interpreted to include dimensions which influence the identities and perspectives that people bring, such as profession, education, parental status and geographic location.Benefits of workforce diversity. Best available talent.Older employees can bring experience and a strong work ethic to the university.Lecturers from other countries, often have an exceptional education, here or abroad, in science and more technical fields.Universities that provide equal opportunities to all workers can select, interview, screen and hire the most educated and experienced workers.More effective execution. Operate more effectively than less-diverse universities due to collective education and experience. Inspire their employees, lecturers and students to perform to the best of their ability.Experienced and educated people tend to be better at planning, time management, goal setting, work delegation and projects completed on time. Negative impacts of workforce diversity.Unresolved conflict.Lecturers and students that come from different cultural backgrounds have different perspectives on how to handle issues or concerns that arise. No parallel understandings between lecturers, students and workers prohi bit effective resolution of conflicts.Poor communication.Different countries and different native languages of students and lecturers prohibit clear and meaningful communication between them.Train the family of the university on cultural awareness and tolerance of differences to encourage them to openly discuss their different viewpoints on things as opposed to avoiding interaction or getting into conflict.Examples of workforce diversity in International Islamic University Malaysia.Lecturers. Many lecturers of IIUM come from different countries such as Russia, Japan, Uzbekistan, Bangladesh and so on. Workforce diversity allows IIUM to choose the IONbest lecturers to serve and educate their students.Students. Students of IIUM not only come from local citizens but also come from other countries such as Brunei Darussalam, Middle East countries and others. IIUM only selects the best students to be in this university.

Rastafarian religion Essay

Rastafarian religion and everything it includes and goes around is under a strict eye of Jamaican people as well as anthropologists and sociologists on the island and from nearby countries. In fact, this culture splashed out of the current residents of Jamaica (its population) moved to this place mainly from Ethiopia. Noel Leo Erskine could talk about Rasta and followers of this cult, as this author has a clear idea of what it is entirely. He could duly count down a period of time to shape the prerequisites and consequences of Rastafarian culture on Jamaica and its impact on African race and the values of bringing in something ethnically pure and original. On the other side, Anthony F. C. Wallace provides a theoretical approach toward getting indigenous peoples right. It is all about the anthropological implementation in each among most applicable approaches. The book by Erskine is a so-called material to apply to Wallace’s anthropological perspective. It means that the overall analysis of Erskine, as a person who grew up and lived on Jamaica, encounters theoretical touches provided by Wallace. As far as might be seen, it would be fair to make it plain by dint of purely Jamaican suggestions and assumptions by Erskine proved or matched with the theoretical side of Rastafarian religion outlined by Wallace. First of all, it is vital to admit that the sociology of religion is of interest for Wallace in his anthropological research. The author sincerely points out that each among religions (especially those spread over indigenous people or ethnically unique communities) should be recognized and further analyzed through sociology and anthropology aligned to make out the gist of any religion influencing social equilibrium within the society. In this respect Wallace remarks the following idea: My own personal feeling is that sociological viewpoints (including much social anthropology) tend to focus on the scaffolding and milieu of religion rather than on religion itself, and that religion can best be understood from a combination of psychological and cultural points of view (Wallace, 1966, p. vii) Such idea is well provided by Erskine who tends to be accurate in identifying the so-called â€Å"stacks† of Rasta among Jamaican. As a matter of fact, when Wallace grabs more attention to the factors (anthropological and sociological) or environment in which a definite religion appears, Erskine highlights a historical as well as personal background to interpret it correctly. In this case one should keep it in mind that Noel Erskine covers in his book the social issue of Rastafarians in its ethical and religious parameters. Erskine admits that due to the start of the Rastafarian movement by Marcus Garvey and the summer of Rasta owing to Bob Marley this religion became remarkable worldwide (Erskine, 2007). Thus, it fulfilled beliefs of all African Ethiopian people on Jamaica, as Jamaicans by origin. To make it clear, one should understand that due to the religious pivot black people on Jamaica do not need to be repatriated to Ethiopia, as they have got their spiritual beginning on this island and in the Rastafarian peaceful ideology. The Wallace’s framework of the religions formation presupposes the fact that people should be apt at creating their values (Wallace, 1966). These ones bear specific traits peculiar to each among individuals (believers). â€Å"Scaffolding† of a religion is definitely a historical process which requires time and people’s efforts to make it grow in a right direction. Providing an idea of the God, as a black figure, was challenging in a country under British supervision since 1655 up to the period of decolonization (Erskine, 2007). By the way, like in many nations, there were people to raise the feeling of personal uniqueness of Jamaican. Garvey and Marley are symbolically identified in the book by Erskine, as the national heroes and holy people who could make the significance of Jah and Rasta higher amid Christian (Catholic) trends (Erskine, 2007). Wallace in his theoretical ramifications tries to investigate religion in its dynamics and characteristic features by means of finding out the â€Å"meaning of religion in some psychological or sociological function† (Wallace, 1966, p. 51). This corresponds to the way of Erskine’s discussion when he appeals to the mentality of Jamaican people and their strong will for freedom. Religion should unite people for some unique and cutting edge idea. In case with Rastafarians it is so, since it helps Jamaican people find their place â€Å"under the sun of Jamaica. † Religious prospects underlined in the research by Erskine go around the focal point stated as follows: â€Å"God is an African† (Erskine, 2007, p. 158). This strong claim has a background implemented solely in the Rastafarian beliefs and its philosophical and social meaning for Jamaican people. The psychological milieu of the aforementioned statement can be explained in some ways, because God is the manifestation of a definite people’s â€Å"attraction, desire, and union as the fulfillment of desire† (Allen, 1978). Hence, it is possible to say that Erskine has all grounds to state that for Africans God should be an African only. From the anthropological point of view this sounds quite logical, as it is full of characteristic features referred to the history, sociology, philosophy and psychology of Rasta since its formation into a separate religion of African residents on Jamaica. Thus, Wallace’s arguments in describing religion are appropriate to how Erskine points out Rastafarian religious framework and its cultural as well as social value for Jamaicans. This idea can be supported by the excerpt from the Bible where it is told about the importance of Ethiopian people who were in touch with Israeli people in ancient times. This fact cannot but boost the morale African people and their dedication to Christian God but in terms of Rasta. Erskine builds up a strong and biblically supported assumption growing into a statement that â€Å"the exodus will be a return to Ethiopia, the Promised Land† (Erskine, 2007, p. 38). It is when Wallace tries to avoid the issue of meaning in his academic research on the religion in its description and proper formation (Wallace, 1966). Interestingly to admit that the entire picture of Rastafarian religion and its place among the rest of religious trends and ideologies is fully developed and structured. To sum up, the theoretical approaches stated by Anthony F. C. Wallace promote an academic framework for the ideas on Rastafarian religion outlined in the book by Noel Leo Erskine. The anthropological and sociological views which Wallace made cornerstone in his observation of religion on the whole fit the claims and the approach (historical) chosen by Erskine. All in all, the philosophical treatment prescribed to Rasta does not go aside from philosophies included in most popular religions of the world. Reference Allen, D. (1978). Structure and creativity in religion: hermeneutics in Mircea Eliade’s phenomenology and new directions. New York, NY: Walter de Gruyter. Erskine, N. L. (2007). From Garvey to Marley: Rastafari Theology (History of African-American Religions). Boca Raton, FL: University Press of Florida. Wallace, A. F. (1966). Religion; an anthropological view. New York: Random House.

Self Perception Is Crippled From One s Image - 1197 Words

Studies show that some of the leading symptoms of depression are self-hatred and distortion of one’s image. In the United States alone, over six million men have depression each year. Usually media advertises the false images and standards of today’s society, which then leads to an alternation of one’s self-understanding. However, every once in a while a film breaks through with an accurate portrayal of the issues occurring in our nation. Through it’s authentic illustrations of modern-day culture and beliefs, Fight Club suggests that self-perception is crippled from one’s surrounding environment. To start off, the controversy behind stereotypical gender roles plays a large part in one’s character and self confidence. Men and women are thought to be very different from each other which proves that â€Å"culturally normative ideas of masculinity are sociologically constructed sets of rules that govern male behaviors, from authorizing male emot ions - tough emotions are okay; emotions of vulnerability are not - to authorizing male sex roles, the heterosexualization of desire, for instance†. This quote by Terry Lee perfectly explains the standards that men are expected to live up to due to popular belief. When Jack loses his apartment, he realizes he has nothing, not even a piece of furniture or material, to reassure him of his masculinity. This sends him into a downward spiral of self-misconception. One observes his reckless decision to fight instead of surrendering to emotions asShow MoreRelatedThe Love Song of J. Alfred Prufrock1729 Words   |  7 Pagesand befriended fellow expatriate Ezra Pound, who was very impressed with the quality of Eliot’s work. 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