Contemporary Progress on Single-Atom Electrocatalysts for H₂ Evolution and CO₂ Reduction Reaction: Insights,...

Single-atom catalysts (SACs) are perceived as the state-of-the-art of electrocatalysts for sustainable fuel-forming reactions like hydrogen evolution reaction (HER) and carbon dioxide reduction reactions (CO₂RR) on account of their exceptional atomic utilization efficiency, surged activity per loading, robust chemical interactions with coordination atoms, and product selectivity. Nevertheless, electrocatalysts based on SACs endure hurdles in terms of scalability and sustainability, as these catalysts may agglomerate during reactions. Additionally, issues related to cost-effectiveness, mass transfer limitations, and standardization render it particularly difficult to elucidate reaction mechanisms at the atomic level. This review ruminates on recent advancements in SACs for electrocatalytic HER and CO₂RR. Initially, the review explores an overview of the basic electrocatalytic processes and important electrochemical variables to evaluate HER and CO₂RR, followed by a brief overview of emergent advancements in SACs as electrocatalysts. Furthermore, different perspectives on synthetic pathways and specific optimization methods were emphasized, focusing on electronic structures, stabilization mechanisms, metal-support interactions, and coordination environments for addressing the potential bottlenecks linked to the types of multielectron processes adopted by the scientific community to boost the selectivity and efficiency of SACs. Ultimately, the challenges and viewpoints regarding the advancement of SACs within the HER and CO₂RR reactions are elucidated.