Direct H2O2 synthesis

All the catalysts supported on TiO₂ were tested in the direct H₂O₂ synthesis. Direct H₂O₂ synthesis experiment was carried out in a stainless-steel semibatch autoclave with a volume of 50 mL. Briefly, 5 mg of supported catalyst, 5.54 g of MeOH, and 3.0 g of H₂O (both HPLC grade) were added to the autoclave. Then purged three times with O₂ (0.4 MPa) to the autoclave, and with filled with O₂ (0.4 MPa) and 5% H₂/Ar (3.6 MPa) until the total pressure of 4.0 MPa at room temperature. All experiments were performed in an ice-water bath and kept continuous stirring (1200 rpm) of reaction time for 15 min. The reaction was carried out at zero Celsius because it is much safer and easier to carry out in the lab. We also investigated the reactivity of the catalyst at room temperature for comparison. The producibility of the Pd_L/PdSn-NW catalyst at room temperature is slightly lower than that performed at zero Celcius in the direct H₂O₂ synthesis (Supplementary Fig. ³⁵). Control experiments are also performed by varying the stirring rate from 100-1200 rpm, and varying the catalyst mass from 3 to 10 mg using autoclaves having different volumes (50 mL and 100 mL). All these experiments show similar H₂O₂ producibility under these conditions. Therefore, it indicates that there are no interphase mass transfer constraints in the reaction under the present conditions (Supplementary Fig. ³⁶).