Reversible ultrafast switching of surface thermodynamics is highly desirable for hydrogen storage and catalysis yet remains elusive at the nanoscale. Here we demonstrate that photoinduced ferroic-order switching in two-dimensional ionic ferroelectric monolayers enables rapid, reversible control of hydrogen binding. In TiGeSe3, carrier-density-driven redistribution of transition-metal 3\textit{d} orbital occupations triggers a sequential evolution from the ferroelectric ground state to paraelectric phases with staggered or Zig-Zag antiferromagnetic order. This switch continuously tunes the hydrogen adsorption free energy from 0.33 to 1.11 eV, shifting the interface from near-thermoneutrality to spontaneous desorption. Nonadiabatic dynamics indicate that electron-phonon coupling promotes nonthermal H release, while picosecond carrier recombination rapidly restores the initial ferroic order, closing an ultrafast reversible cycle. Generality is further validated in AgBiP2Se6 and CuInP2S6, establishing ferroic order as an optically addressable knob for dynamic thermodynamic reconfiguration beyond static design.
@article{arxiv.2605.24378,
title = {Light-Driven Ferroic Switching Enables Reversible Control of Hydrogen Adsorption Thermodynamics},
author = {Xueqing Wan and Zhenlong Zhang and Charles Paillard and Jian Zhou and Jinyang Ni and Chuanlu Yang and Zhijun Jiang and Laurent Bellaiche},
journal= {arXiv preprint arXiv:2605.24378},
year = {2026}
}