Hydrogen dissociative adsorption and Au(III) ions reduction on gold nanoparticles in aqueous solutions

B.G. Ershov, E.V. Abkhalimov, R.D. Solovov

A.N. Frumkin Institute of Physical Chemistry and Electrochemistry RAS

The shift of the localized surface plasmon resonance (LSPR) band of gold nanoparticles to shorter wavelengths upon saturation of the hydrosol with hydrogen is used as a tool to study the electrochemical processes on the particle surface. It is shown that dissociative adsorption of hydrogen takes place on the surface of a particle and results in a migration of a proton into the dispersion medium, while the electron remains on the nanoparticle, i.e., a hydrogen nanoelectrode is formed. It is shown that Au(III) ions can be reduced on the gold nanoelectrodes. A thermodynamic scheme explaining the shift of the LSPR band is used to explane the peculiarities of the Au(III) ions reduction. The reduction rate does not depend on the ion concentration and varies linearly with pH. The observed correlations are explained in terms of a simple model of electrochemical processes taking place on the nanoparticle as an electrode. It is shown that with increase in the particle size, its capacity for dissociative adsorption of hydrogen decreases and the Au(III) reduction slows down.