Decomposition of formic acid over silica encapsulated and amine functionalised gold nanoparticles

- Small and uniform gold nanoparticles are encapsulated in amine functionalised silica.
- The catalyst is highly active for vapour phase decomposition of formic acid into H2.
- Kinetic isotope labelling indicates that the formation of H2 is rate-limiting.
- In situ ATR-FTIR indicates that the active site is an amine functionalised Au atom.

Formic acid has recently attracted considerable attention as a safe and convenient source of hydrogen for sustainable chemical synthesis and renewable energy storage. Here, we show that silica encapsulated and amine functionalised gold nanoparticles are highly active catalysts for the production of hydrogen by vapour phase decomposition of formic acid. The core-shell catalysts are prepared in a reverse micelle system that makes it possible to control the size of the Au nanoparticles and the thickness of the SiO2 shells, which has a large impact on the catalytic activity. The smallest gold nanoparticles are 2.2 ± 0.3 nm in diameter and have a turnover frequency (TOF) of up to 958 h−1 at a temperature of 130 °C. Based on detailed in situ ATR-FTIR studies and results from kinetic isotope labelling experiments we propose that the active site is a low-coordinated and amine functionalised Au atom, while H-assisted formate decomposition into CO2 and H2 is the rate limiting step.

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