Liquid Metals in Catalysis for Energy Applications

To keep up with the fast-paced transitioning of the global energy sector, which is constantly thriving to enable reliable, economic, and sustainable energy production, catalysis research has been required to continuously evolve in response. The challenges in the existing systems are predominantly due to dependencies on heterogeneous solid catalysts that are susceptible to coking. In this respect, liquid-metal (LM) catalysts have been demonstrated to have a critical advantage over conventional catalysts. Recently, LMs acquired a place in catalysis, with a reputation often synonymous with interesting properties and a remarkable ability to break trade-offs between homogeneous and heterogeneous catalysis. This review bridges the fundamental principles of LM research and the recent advances in LM-based thermal and electrochemical catalysis for energy applications. Moreover, emerging approaches for the improved utilization of LMs are outlined, and the concepts requiring greater research attention that could enable the development of exciting energy solutions are highlighted. The field of liquid-metal (LM) catalysts is attracting significant attention, owing to their unique properties and their exceptional ability to support homogeneous and heterogeneous catalysis. Nevertheless, LM chemistry is still in its infancy and substantial contributions are required to make the most of these catalysts. This review presents an overview of the fundamental properties of LMs that govern the applicability of these state-of-the-art catalysts. Due to the close association between catalytic activity and the phase and structure of the catalyst, current characterization and modeling methods that are available for LM-based process analysis are outlined. Moreover, the use of both supported and unsupported LM catalysts in thermal and electrochemical catalytic processes for energy applications is showcased, and factors underlying their efficacy are explored. To date, the most common reaction design approach in LM thermal catalysis involves the use of bubbling-column reactors. The dependence of current investigations on a single-design model instigates the need to reassess this approach and evaluate other attractive reactor models, such as spraying or pulsing. Future advancements in LM catalysis and progress toward commercialization in this field necessitate research on several fronts, including the development of new LM-characterization methods, to enable characterization of the LM bulk that is currently lacking and facilitate in situ analysis; deploying innovative reactor designs to maximize liquid-gas interactions; and refining catalyst design to improve catalytic activity and increase application specificity through alloying. Liquid metals have recently gained momentum in catalysis for energy applications. In this review, we detail the fundamental properties of liquid metals that promote their use as catalytic materials. We focus on the use of liquid metals in thermal and electrocatalysis and explore advancements in emerging catalytic approaches. This review outlines the future research avenues for the liquid-metal-catalysis field and serves to lay out a roadmap for the deployment of liquid-metal catalysts in energy applications.