Rare-earth single-atom mediated twin S‑scheme homojunction-heterojunction for highly selective photocatalytic C-N coupling toward urea synthesis

Lattice-matched hetero-phase interfaces suppress defect charge transport resistance. • Dual built-in fields boost the separation and migration of photogenerated carriers, and interfacial kinetics. • Rare-earth single atoms' 4f electrons tune active-site electron density and coordination for N 2 activation and C-N coupling. • Er/BiVO 4 -ZnCdS single atom twin S-scheme homojunction-heterojunction catalyst: urea rate 136.78 μmol·g -1 ·h -1 . Engineering twin S-scheme heterojunctions is a promising strategy for photocatalytic systems. Nevertheless, constructing such dual S‑scheme architectures with three distinct catalysts often induces lattice mismatch and weak interfacial coupling, which invariably erects formidable charge-transfer barriers that compromise deep N 2 activation kinetics and selective C-N coupling efficiency. Herein, a novel strategy based on rare-earth single-atom introduction to induce phase transformation and construct single-atom twin S‑scheme homojunction-heterojunction catalysts is developed. The lattice-matched hetero-phase interfaces minimize defect-induced charge transport resistance, whereas dual built-in electric fields cooperatively expedite photogenerated carrier separation and migration, and concurrently optimize interfacial charge transfer dynamics. Er single atoms possess a distinctive 4 f electronic configuration, which enables precise modulation of the electron density distribution and coordination microenvironment of catalytic active sites, conferring remarkable advantages in boosting N 2 activation and steering selective directional C-N bond coupling. Remarkably, the optimized catalyst achieved a urea yield rate of 136.78 μmol·g −1 ·h −1 with 95.82% selectivity. This study demonstrates a synergistic integration strategy combining single-atom engineering with phase-junction and heterojunction design for high-efficiency solar-to-chemical conversion. Download: Download high-res image (125KB) Download: Download full-size image A novel rare-earth single-atom strategy is developed to induce phase transformation and construct twin S-scheme homo-heterojunctions. Lattice-matched interfaces and dual built-in electric fields accelerate carrier separation, while unique 4 f electronic structures modulate active sites for efficient N 2 activation and C-N coupling. The optimized catalyst achieves a urea yield of 136.78 μmol·g −1 ·h −1 with 95.82% selectivity.