Metal-free hydrogen generation from seawater and silicon waste: a circular approach

Hydrogen is a primordial energy carrier and industrial raw material that will play a crucial role in future energy transition and de-fossilization ambitions. Silane hydrolysis represents an underexplored approach to hydrogen generation, yet most known systems have thus far focused on noble-metal catalysis. Herein we report a highly active transition metal-free method for the production of hydrogen from (sea)water and hydrosilanes, relying on the unique combination of simple bases as catalyst, and dimethyl sulfoxide as promoting solvent, assisted by mechanistic and computational studies. Remarkably, the hydrolysis of phenylsilane achieved a turnover frequency (TOF) of 5116 min–1, far superior to existing metal-free systems (TOF ≤ 8 min–1), and even surpassing noble-metal catalysts (TOF ≤ 170 min–1). The developed method rapidly generates hydrogen directly from seawater, applying polymethylhydrosilane (PMHS), a silicon industry waste, with rates up to 70.2 molH2/gcat/h. Notably, we have demonstrated the recyclability of the solvent, and re-use of the by-products formed during PMHS hydrolysis. Thus, the polysiloxane by-products were efficiently depolymerized into functional chlorosilane monomers, which are suitable for the design of new high-value silicon polymers. These findings highlight the broader applicability and circularity of our integrated approach.