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

Mielby, Jerrik, Kunov-Kruse, Andreas Jonas, Kegnæs, Søren
Journal of catalysis 2017 v.345 pp. 149-156
Fourier transform infrared spectroscopy, active sites, carbon dioxide, catalysts, catalytic activity, formates, formic acid, gold, hydrogen, isotope labeling, micelles, nanogold, renewable energy sources, silica, synthesis, temperature, vapors
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±0.3nm in diameter and have a turnover frequency (TOF) of up to 958h⁻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.