ABSTRACT

Oxygen reduction reactions (ORRs) are unanimously a key factor of system performances in bioelectrochemical systems (BESs), low-temperature fuel cells, and generally in several electrochemical platforms. Platinum (Pt)-based catalyst is the finest electrocatalyst for ORR in BESs; however, it is constrained by its low abundance, high price, and poor catalytic durability in an electrochemical setup for cathodic reaction kinetics. In recent years, significant efforts in trimming the metal-based catalyst up to nanoscale to cater high performance of ORR have been explored. Still, there are many opportunities to improve catalyst performance at cathode through proper selection of an efficient low-cost metal-based ORR catalyst. Molybdenum (Mo) with its multi-dimensional form as 2D and 3D layers and synergistic combination with other non-metals offers prospects of extraordinary performance as low-cost metal-based ORR catalyst over the Pt in delivering enhanced ORR potential. The present review throws light on current requirements of a sturdier catalyst material and thus provides a comprehensive review on the continuing efforts in exploring the possibility of Mo as a low-cost metal-based ORR catalyst. This literature analysis would enlighten the significance of ORR in BESs, followed by the electrochemistry of Mo-based cathodic catalyst, its underlying mechanism and performance limiting factors in the operation of ORR. Moreover, the extensive and systematic acumen in the context of Mo-based catalytic formulations for increased ORR potentials including nano-composite Mo-cathode catalyst; development of Mo-catalyst with varied configurations; carbon-supported Mo-catalyst; morphological changes; surface area modifications; and Mo-coupling with other transition metal and its derivatives were discussed in great detail to provide prospective application of Mo-based catalyst. Lastly, numerous opportunities and projections for future research in fabrication, juxtaposition, and implementation of Mo-based cathodic catalysts and consequent recommendations were discussed as conclusive remarks for bringing out the state-of-the-art review on this subject.

摘要

氧还原反应 (ORR) 一致是生物电化学系统 (BES)、低温燃料电池以及多种电化学平台中系统性能的关键因素。铂（Pt）基催化剂是 BES 中最好的 ORR 电催化剂；然而，它受到丰度低、价格高以及在阴极反应动力学电化学装置中催化耐久性差的限制。近年来，为了满足 ORR 的高性能，人们在将金属基催化剂缩小到纳米尺度方面做出了重大努力。尽管如此，通过正确选择高效、低成本的金属基 ORR 催化剂，仍有很多机会提高阴极催化剂的性能。钼 (Mo) 以其 2D 和 3D 层的多维形式以及与其他非金属的协同组合，作为低成本金属基 ORR 催化剂，比 Pt 具有卓越的性能前景，可提供增强的 ORR 潜力。本综述阐明了当前对更坚固的催化剂材料的需求，从而对探索 Mo 作为低成本金属基 ORR 催化剂的可能性的持续努力进行了全面回顾。该文献分析将阐明 ORR 在 BES 中的重要性，随后介绍钼基阴极催化剂的电化学、其基本机制以及 ORR 运行中的性能限制因素。而且，在钼基催化配方方面具有广泛而系统的智慧，可提高 ORR 潜力，包括纳米复合钼阴极催化剂；不同构型Mo催化剂的开发；碳载钼催化剂；形态变化；表面积修改；并对Mo与其他过渡金属及其衍生物的偶联进行了详细的讨论，为Mo基催化剂的应用提供了前景。最后，讨论了钼基阴极催化剂的制造、并置和实施方面的未来研究的大量机会和预测以及随之而来的建议，作为对这一主题进行最新审查的结论性评论。