Enhanced visible-light hydrogen production from lactic acid using Cu-doped TiO2 photocatalysts synthesized via supercritical antisolvent process

Developing highly active TiO 2 -based photocatalysts capable of operating under visible light remains a key challenge for scalable solar-to-hydrogen conversion. In this work, we report a significant performance enhancement achieved by SAS micronization to produce Cu-doped TiO 2 photocatalysts with finely tuned structural and electronic properties. Comprehensive characterization (XRD, Raman, FESEM–EDX, FTIR, UV–vis, PL, SSA and XPS) reveals that SAS processing promotes homogeneous Cu incorporation, lattice distortion along the c-axis, and the generation of oxygen vacancies, collectively enabling band-gap narrowing and improved visible-light absorption. Among the investigated samples, 2Cu–TiO 2 SAS exhibited the highest H 2 production (4040 μmol L −1 after 4 h), outperforming both non-micronized analogues and literature benchmarks. Photocatalytic tests combined with D 2 O experiments demonstrate that lactic acid serves as the primary hydrogen source. A kinetic model derived from the Langmuir–Hinshelwood framework, incorporating substrate inhibition at high lactic-acid concentrations, accurately reproduces the experimental trends and predicts photocatalytic performance. When normalized to catalyst mass, lactic-acid moles, and irradiation power, the 2Cu–TiO 2 SAS photocatalyst achieves 941 μmol H 2 gcat −1 mol LA −1 W −1 , up to twenty times higher than reference CdS-based systems. The novelty of this work lies in the use of the supercritical antisolvent (SAS) process to achieve improved Cu incorporation into the TiO 2 lattice, enabling enhanced visible-light-driven hydrogen production from lactic acid compared to conventionally prepared materials.This study establishes SAS-micronized Cu–TiO 2 as a highly efficient platform for visible-light-driven hydrogen production.