Performances and structural evolution of a new critical raw materials-free catalyst, synthesized from spent lithium-ion batteries, for solar-driven CO₂ conversion

Abstract

The development of next-generation catalysts is crucial for advancing sustainable CO₂ conversion technologies and addressing pressing environmental challenges. This work integrates green chemistry principles by combining CO₂ valorization, waste recovery, and renewable energy use, demonstrating a sustainable and circular approach to catalyst discovery and application. This study investigates the functional and structural properties of a novel malate-based catalyst synthesized starting from spent lithium-ion battery waste, developed after lithium recovery. Under solar photothermo-catalytic conditions, the catalyst showed excellent CO₂-to-solar fuel conversion (CO and CH₄) at low temperatures, with a CH₄ selectivity > 80%, compared to classical catalysts based on critical raw materials. X-ray pair distribution function analysis was used for the first time to reveal a significant structural transformation: the catalyst undergoes a transition from a crystalline resting state to an amorphous, catalytically active shell during reaction, significantly enhancing the material efficiency. A preliminary sustainability analysis shows that the embodied energy and carbon footprint values associated with the synthesis of the new malate are comparable with those of the classical catalysts used for this application, based on ceria, titania, and bismuth.