Das Debarati, Prakash Jyoti, Bandyopadhyay Anisha, Balhara Annu, Goutam U K, Acharya Raghunath, Gupta Santosh K, Sudarshan Kathi
Radiochemistry Division, Bhabha Atomic Research Centre Mumbai-400085 India
Homi Bhabha National Institute Anushaktinagar Mumbai - 400094 India.
RSC Adv. 2024 Jun 3;14(25):17801-17813. doi: 10.1039/d4ra03360d. eCollection 2024 May 28.
Aliovalent doping in ceria and defect engineering are important aspects in tuning the properties of ceria for advanced technological applications, especially in the emerging field of electrocatalytic water-splitting for harvesting renewable energy. However, the ambiguity regarding the choice of dopants/co-dopants and ways to deal with the size difference between dopants and lattice hosts remains a long-standing problem. In this study, ceria was aliovalently codoped with Sc and La while keeping the total concentration of dopants constant; the ionic radius of the former is smaller and that of the latter is larger than Ce. Variations in the relative amounts of these dopants helped to modulate the effective ionic radii and match that of the host. A systematic study on the role of these aliovalent dopants in defect evolution in ceria and in modulating the Ce fraction using powder XRD, Rietveld refinement, positron annihilation lifetime spectroscopy, X-ray photoelectron spectroscopy, Eu photoluminescence, and Raman spectroscopy is presented here. The evolved defects and their dependence on subtle factors other than charge compensation are further correlated with their electrocatalytic activity towards oxygen evolution reaction (OER) in alkaline medium. The catalyst with an optimum defect density, maximum Ce fraction at the surface and the least effective ionic radius difference between the dopants and the host demonstrated the best performance towards the OER. This study demonstrates how effective ionic radius modulation in defect-engineered ceria through a judicious choice of codopants can enhance the catalytic property of ceria and provides immensely helpful information for designing ceria-based heterogeneous catalysts with desired functionalities.
在二氧化铈中进行异价掺杂和缺陷工程是调整二氧化铈性能以用于先进技术应用的重要方面，特别是在新兴的用于获取可再生能源的电催化水分解领域。然而，关于掺杂剂/共掺杂剂的选择以及处理掺杂剂与晶格主体之间尺寸差异的方法仍存在长期的模糊问题。在本研究中，二氧化铈被异价共掺杂了Sc和La，同时保持掺杂剂的总浓度不变；前者的离子半径小于Ce，后者的离子半径大于Ce。这些掺杂剂相对含量的变化有助于调节有效离子半径并使其与主体相匹配。本文利用粉末XRD、Rietveld精修、正电子湮没寿命谱、X射线光电子能谱、Eu光致发光和拉曼光谱，对这些异价掺杂剂在二氧化铈缺陷演化以及调节Ce含量方面的作用进行了系统研究。所产生的缺陷及其对除电荷补偿之外的细微因素的依赖性，进一步与它们在碱性介质中对析氧反应（OER）的电催化活性相关联。具有最佳缺陷密度、表面最大Ce含量以及掺杂剂与主体之间最小有效离子半径差的催化剂对OER表现出最佳性能。本研究展示了通过明智地选择共掺杂剂在缺陷工程化的二氧化铈中进行有效离子半径调制如何能够增强二氧化铈的催化性能，并为设计具有所需功能的二氧化铈基非均相催化剂提供了极为有用的信息。
