Pioneering sustainable energy solutions with rare-earth nanomaterials: Exploring pathways for energy conversion and storage

Rare-earth-nanomaterials (RE-NMs) have surged to the forefront of cutting-edge research, captivating scientists and engineers alike with their unprecedented potential and transformative applications with the primary sources for these materials being monazite (lanthanide concentrate) used to produce Rare Earth Oxides (REOs). RE-NMs are nanomaterials derived from the 17 Rare Earth Elements (REEs), encompassing the 15 lanthanides (similar to La, Ce, Nd, Ho, Pr, Eu, Tm, Sm, Yb, Er, Lu, Gd, Tb, Pm, and Dy), Sc and Y are employed in advanced technologies for their unique nanoscale properties in applications such as electronics, magnets and catalysts. Rare earth elements are classified into three distinct categories: light rare earth elements (LREE), medium rare earth elements (MREE), and heavy rare earth elements (HREE). These elements are prized for their unique electronic configurations, metal radii and atomic numbers, which endow them with extraordinary structural, electronic, chemical bonding, optical and electrical properties. Throughout the ages, there has been a tremendous and crossdisciplinary fascination with these exceptional materials, exploring their myriad applications from active doping and co-doping to tri-doping and innovative composites, all driven by the quest for groundbreaking solutions in energy conversion and storage towards a more sustainable world. This critical review provides a broad overview of recent progress in the design and development of rare-earth-based nanomaterials. It addresses: (1) the discovery and sources of rare-earth-based nanomaterials, (2) methods for synthesizing RE-NMs and fabricating RE-NM thin films and (3) the exploration of RE-NMs in applications including solar cells, electrochemical devices and supercapacitors, along with their diverse applications across multiple fields. To conclude, this review summarizes current advancements and offers stimulating perspectives on the challenges and future research directions in the realm of RE-NMs. This review aims to open new research pathways for developing recycling methods and cutting-edge renewable energy nanomaterials (RE-NMs) from residue waste. Utilizing these materials in renewable energy applications could minimize environmental impact and pave the way for innovative uses of photocatalysts, solar cells and supercapacitors contributing to sustainable energy solutions in the future.