On-off control for on-demand H2 evolution upon Si-H bond hydrolysis: A combined experimental and theoretical study

Although significant advances are achieved in the exploration of new and high-efficiency catalysts for H2 pro-duction from the hydrolysis of B-H bonds, such as NH3BH3 and NaBH4, it is still a severe challenge to explore controllable H2 evolution upon Si-H bond hydrolysis. Herein, we report unprecedented on-offswitch of the controlled nanocatalyzed H2 evolution upon hydrolysis of Si-H bond in tetramethyldisiloxane (TMDS) including mechanistic and DFT studies of this reaction. A series of carbon nanotube-stabilized Pd, Au, Rh, Pt and Ru nanohybrid are utilized as highly efficient nanocatalysts for the controlled H2 evolution upon Si-H bond hy-drolysis. Among them, the optimal Pd/carbon nanotube (CNT) nanohybrid exhibits the highest catalytic per-formance, with a TOF of 4164 h-1, in H2 evolution upon TMDS hydrolysis at 30 degrees C. Kinetic studies including Kinetic Isotope Effect with D2O and DFT calculations are in favor of concerted Si-H and O-H cleavages in the rate -determining step involving SiO-H-OH hydrogen bonding that facilitates water activation. A new and highly selective on-off switch is achieved via a Zn2}/EDTA-2Na system for on-demand H2 evolution upon Si-H bond hydrolysis; this system proceeds by inhibition and activation regulation of surface-active sites on the catalyst. The detailed physical characterizations (particularly XRD and XPS) and DFT calculations have confirmed that Zn2} ions are bound to the PdNP surface, inhibiting surface-active sites by stereo-electronic interaction, which results in H2 evolution switch off. H2 evolution is then switched back on by using EDTA-2Na due to its excellent coordination to Zn2} ions, reactivating these surface-active sites.

Automated summary

A controllable nanocatalytic switch for H2 evolution via hydrolysis of Si-H bonds is reported. Carbon nanotube-stabilized Pd, Au, Rh, Pt, and Ru nanohybrids are utilized as highly efficient nanocatalysts. The switch is achieved using a Zn2+/EDTA-2Na system, which inhibits or activates surface-active sites on the catalyst.