目前,电催化分解水制备氢气和氧气技术成为解决能源需求和环境污染问题的重要措施之一。电解水反应由两个核心半反应组成:阴极析氢反应(HER)和阳极析氧(OER)反应,然而相比于快速的阴极析氢反应,阳极析氧反应涉及四电子转移过程,动力学缓慢。因此,开发高催化活性,高稳定性电催化剂提高电解水氧析出效率受到科研工作者的广泛关注。一些贵金属氧化物,如Ru O2和Ir O2,在析氧领域表现出优异的电催化性能,但是由于贵金属储量稀少、价格昂贵,严重限制了其广泛应用。因此开发储量丰富、催化性能良好的非贵金属材料,如非金属(C、N、P),过渡金属(Ni、Co、Fe)等化合物均成为析氧电催化剂领域的研究热点。本工作基于研究非贵金属基电催化剂,通过简单的水热反应得到以导电石墨毡为基体,负载过渡金属钴、镍氢氧化物和钴磷酸盐,作为自支撑结构工作电极,在中性电解环境下对其OER电催化性能进行探究。首先,在石墨毡表面负载金属钴的氢氧化物,探究水热温度,反应时长,钴、镍摩尔比,氟化铵添加量对活性组分的影响,得到一系列电催化剂。通过物理表征和电化学测试,系统地证实过渡金属钴作为活性位点,氟化铵添加量0.3 g,水热温度120℃反应7 h的条件,得到Co(OH)F作为活性组分修饰石墨毡电催化剂(Co(OH)F@GF)在中性电解液(0.1 M PBS)中具有最高的电催化活性:到达电流密度5 m A cm-2所需过电位为580 m V,电子转移阻抗225Ω,在较高的析氧电位2.01 V(***)下长时间反应10 h保持20 m A cm-2不变。其次,以Co(OH)F@GF为前驱体材料,二次水热发生原位磷酸化反应,得到磷酸钴修饰石墨毡电催化剂(Co3(PO4)2@GF)。SEM表征显示二次磷酸化反应后,活性组分由层状结构转换为松针状,经过对磷酸化时长的探究,证明水热反应10小时生成磷酸钴,在中性电解液中,与碳纤维基体、前驱体材料相比,OER催化活性得到很大程度提高:到达电流密度5 m A cm-2所需过电位为530 m V,电子转移阻抗117Ω,在较高的析氧电位2.01 V(***)下长时间反应10 h保持25 m A cm-2不变。磷酸钴具有良好的导电性,且与导电基体结合良好,有利于电荷转移能力的提高,结合松针状表面形貌,因此获得了更高的电催化析氧性能。
The academic study of engagement has its roots in studies of happiness and of burnout. Happiness consists of three distinct dimensions, namely, pleasure, meaning and engagement. The dimension of engagement is highly r...
The academic study of engagement has its roots in studies of happiness and of burnout. Happiness consists of three distinct dimensions, namely, pleasure, meaning and engagement. The dimension of engagement is highly relevant to a working environment. The positive outcomes that have been linked to engagement have driven much of the research in this field. Living in an increasingly competitive world where performance and competitive advantage guide the thinking patterns it has become important to investigate this concept in a local setting in order to determine its roots, its predictors and the underlying processes that influence and determine engagement. This is because it is not clear what the levels of employee engagement are in Namibian organisations. It is also unclear what the psychological conditions and antecedents of engagement are in Namibian organisations and whether these are consistent with findings elsewhere. In addition to this it also is not clear what the effects of the psychological conditions, and antecedents thereof, are on employee engagement in Namibian organisations. The aim of this study was to investigate the levels of engagement in Namibian organisations as well as the antecedents and underlying psychological conditions that lead to engagement. In this study a cross-sectional survey design was used with a sample of 309 currently employed individuals. A biographical questionnaire together with the Antecedents Questionnaire, Psychological Conditions Questionnaire and Engagement Questionnaire were used as measuring instruments. Statistical analysis in terms of descriptive, factor, correlation, canonical, multiple regression and mediation analyses have been conducted. The results showed that Namibian employees showed higher levels of engagement than those of employees investigated in other areas. In addition, it was shown that rewards, co-worker relations, resources, supervisor relations, job enrichment, self- consciousness, work role fit and org
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