Position-controlled non-metal single atoms on MXene enable high-performance oxygen reduction electrocatalysis

Strategic localization of catalytically active sites within single-atom catalyst (SAC) architectures represents a pivotal determinant of material performance, particularly in two-dimensional (2D) substrates like MXenes, which offer intricate structural complexity and multifarious anchoring potentialities. Despite the burgeoning interest in non-metallic single-atom catalysts, a comprehensive understanding of site-specific loading mechanisms and their consequential catalytic implications remains substantially unexplored. Herein, we systematically investigate the precise incorporation of economically viable non-metallic elements—tellurium (Te) and arsenic (As)—onto Ti₃C₂ MXene, a prototypical 2D material characterized by exceptional structural versatility. Our methodology delineates a nuanced approach to controllable single-atom immobilization, strategically differentiating between vacancy-embedded and surface-supported configurations. Through meticulous experimental design, we demonstrate that Te single atoms strategically integrated within titanium vacancies (C-TeSA-T) manifest superior Oxygen Reduction Reaction (ORR) electrocatalytic performance compared to surface-anchored counterparts (W-TeSA-T). Comprehensive characterization revealed remarkable electrocatalytic metrics, including a half-wave potential of 0.88 V vs. RHE and a limiting current density of 5.65 mA/cm². Synergistic Density Functional Theory (DFT) computations and multi-potential X-ray Photoelectron Spectroscopic (XPS) analyses elucidated the intrinsic mechanistic landscape, conclusively identifying Te single atoms as primary catalytic centers and delineating the rate-determining reaction trajectory. This systematic investigation not only introduces an innovative paradigm for designing cost-effective non-metallic catalysts but also provides fundamental mechanistic insights into the intricate relationship between active site localization and catalytic performance, thereby advancing our fundamental understanding of site-specific catalysis in two-dimensional materials.