Correlations between Synthesis and Performance of Fe-Based PGM-Free Catalysts in Acidic and Alkaline Media: Evolution of Surface Chemistry and Morphology
Correlations between Synthesis and Performance of Fe-Based PGM-Free Catalysts in Acidic and Alkaline Media: Evolution of Surface Chemistry and Morphology
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DOI：
10.1021/acsaem.9b00331
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发表时间：
2019-08-01
影响因子：
6.4
通讯作者：
Atanassov, Plamen
中科院分区：
文献类型：
--
作者：
Artyushkova, Kateryna;Rojas-Carbonell, Santiago;Atanassov, Plamen
研究了无铂族金属（PGM-free）催化剂的合成步骤对表面化学、形貌以及在酸性和碱性介质中对氧还原反应（ORR）的电化学活性的影响。每个步骤都对催化剂活性产生积极影响。在酸性介质中，二氧化硅模板的蚀刻是半波电位增强的主要贡献者，因为在第一热解过程中形成的ORR活性位点变得更容易接近。进一步的处理步骤甚至导致4 e-转移位点的更高的可访问性和利用率。在碱性介质中，第二热解是有利于氧完全还原为水的关键步骤，因为过氧化物的产生显著减少。在每个合成步骤的孔隙率的大的不均匀性表明，该参数需要进一步研究，以达到更好地控制的PGM-自由的催化剂的形态，因为它是一个重要的因素，有助于活性位点的利用率。酸蚀和二次热解增加了介孔和大孔孔隙率。了解每个合成步骤对不含PGM的催化剂的化学组成、形态和ORR活性的影响，为设计提高催化剂性能的合成方案提供了必要的反馈。
The effects of the synthesis steps of a platinum group metal-free (PGM-free) catalyst on the surface chemistry, morphology, and electrochemical activity in acidic and alkaline media toward the oxygen reduction reaction (ORR) were studied. Each step exhibits a positive impact on catalyst activity. In acid media, etching of the silica template is the major contributor to the enhancement of the half-wave potential, as the ORR active sites formed during the first pyrolysis become more accessible. Further processing steps result even in higher accessibility and utilization of the 4e - transfer sites. In alkaline media, the second pyrolysis is a critical step that favors the complete reduction of oxygen to water, as the peroxide production is significantly diminished. The large heterogeneity in the porosity at each synthesis step indicates that this parameter needs to be further studied to attain better control of the morphology of the PGM-free catalyst, as it is an important factor that contributes to the active site utilization. The acid etching and second pyrolysis increase the meso- and macroporosity. Understanding the effects of each of the synthesis steps on the chemical composition, morphology and ORR activity of the PGM-free catalyst provides the necessary feedback for the design of synthetic schemes that increase the catalysts' performance.