On-demand Hydrogen Production from Organosilanes at Ambient Temperature Using Heterogeneous Gold Catalysts

An environmentally friendly (“green”), H2-generation system was developed that involved hydrolytic oxidation of inexpensive organosilanes as hydrogen storage materials with newly developed heterogeneous gold nanoparticle catalysts. The gold catalyst functioned well at ambient temperature under aerobic conditions, providing efficient production of pure H2. The newly developed size-selective gold nanoparticle catalysts could be separated easily from the reaction mixture containing organosilanes, allowing an on/off-switchable H2-production by the introduction and removal of the catalyst. This is the first report of an on/off-switchable H2-production system employing hydrolytic oxidation of inexpensive organosilanes without requiring additional energy.

The GC-FID and GC-MS were performed on a Shimadzu GC-2014 instrument equipped with a Unisole-30T column and a GCMS-QP2010 SE instrument equipped with an Inert Cap WAX-HT capillary column (30 m × 0.25 mm i.d., 0.25 m. Gas-phase analysis was done with an on-line quadrupole mass spectrometer (BELMass-S, BEL Japan, Inc.). The 1 H and 13 C nuclear magnetic resonance (NMR) spectra were recorded on a JEOL JNM-ESC400 spectrometer and the chemical shifts reported in ppm from TMS as a reference. Transmission electron microscopy observations were obtained using an FEI Tecnai G2 20ST instrument operated at 200 kV.

2) Synthesis of Au/HAP
Supported gold NPs were synthesized as follows. The HAP (1.0 g) was soaked in 50 mL of an aqueous solution of HAuCl 4 (2 mM). After stirring for 2 min, 0.2 mL of aqueous NH 3 (10%) was added and the resulting mixture stirred at room temperature for 12 h in an air atmosphere. The obtained slurry was filtered, washed with deionized water, and then dried at room temperature in vacuo. Subsequently, the HAP solid containing Au ions was added to 50 mL of an aqueous solution of KBH 4 (18 mM) and stirred at room temperature for 1 h to yield Au/HAP as a purplish red powder.

5) Large-scale reaction
A large-scale reaction was performed under O 2 bubbling for 12 h. After the oxidation reaction, Au/HAP-NC was filtered and the yield determined by GC analysis. The product was isolated by Kugelrohr distillation.

6) Demonstration of on/off-switching of H 2 production by introduction and removal of Au/HAP-NC (0.5 wt%)
Please see Supplementary Movie 1. Demonstration of on/off-switching of H 2 production by introduction and removal of Au/HAP-NC (0.5 wt%).

7) Utilization of catalytic H 2 -generation system for portable fuel cell
Please see Supplementary Movie 2. Utilization of catalytic H 2 -generation system for portable fuel cell.

8) Comparison with previously reported catalysts 9) Hydrogen production through hydrolytic oxidation of PMHS and TMDS
The generation of equimolar amounts of H 2 through oxidation of PMHS and TMDS was confirmed by GC-TCD analyses. The 1 H NMR analyses indicated that the Si-H bonds of these substrates were completely oxidized after hydrogen production (Supplementaly Figures 6 and 7).