1：Experimental Design and Method Selection:

The study involved synthesizing TiO2 nanosheets (NS) with exposed {001} facets via a solvothermal method using tetrabutyl titanate and hydrofluoric acid, and doping them into MgH2 via ball milling under hydrogen atmosphere. Commercial TiO2 nanoparticles (NP) were used as a comparative catalyst. Characterization included XRD, TEM/HRTEM, SAED, EDS, DSC, TPD, and isothermal de/hydrogenation tests. First-principle calculations (DFT with VASP) were employed to analyze electronic structures and desorption energies.

2：Sample Selection and Data Sources:

Samples included undoped MgH2, MgH2 doped with TiO2 NP (5 wt%), and MgH2 doped with TiO2 NS (3, 5, 10, 15 wt%). Raw materials: Mg powder (99%), TiO2 NP (anatase, 5-10 nm), tetrabutyl titanate (98%), hydrofluoric acid (>40%). Data were obtained from laboratory experiments and theoretical simulations.

3：List of Experimental Equipment and Materials:

Equipment: Planetary ball mill (QM-3SP4, Nanjing), X-ray diffractometer (X’Pert Pro, PANalytical), TEM (Tecnai G2 F20), DSC analyzer (Netzsch STA449F3), Sievert’s type apparatus for hydrogen sorption, Ar-filled glovebox (Mikrouna). Materials: Tetrabutyl titanate (Ti(OBu)4, 98%, aladdin), hydrofluoric acid (HF, >40%, Sinopharm), Mg powder (99%, Sinopharm), TiO2 nanoparticles (anatase, 5-10 nm, 99.8%, aladdin).

4：8%, aladdin). Experimental Procedures and Operational Workflow:

4. Experimental Procedures and Operational Workflow: Synthesis of TiO2 NS: Ti(OBu)4 and HF were mixed in a Teflon-lined autoclave, heated to 180°C for 24 h, washed with ethanol, NaOH, and deionized water, and dried. Synthesis of catalyzed MgH2: Ball milling of MgH2 with catalysts (weight ratios 3:97 to 15:85) under 2 MPa H2 for 4 h with ball-to-powder ratio 40:

5：Characterization:

XRD with Cu Kα radiation, TEM/HRTEM/SAED/EDS for microstructure, DSC and TPD for thermal analysis, isothermal de/hydrogenation tests at various temperatures and pressures.

6：Data Analysis Methods:

XRD data analyzed using Scherrer equation for crystal size. Kissinger method used to calculate activation energy from DSC data. First-principle calculations performed with VASP using DFT-PBE, GGA+U, and van der Waals corrections for electronic structure and desorption energy analysis.