  Simple, yet versatile, methods to functionalize graphene flakes with metal
(oxide) nanoparticles are in demand, particularly for the development of
advanced catalysts. Herein, based on light-induced electrochemistry, a
laser-assisted, continuous, solution route for the simultaneous reduction and
modification of graphene oxide with catalytic nanoparticles is reported.
Electrochemical graphene oxide (EGO) is used as starting material and
electron-hole pair source due to its low degree of oxidation, which imparts
structural integrity and an ability to withstand photodegradation. Simply
illuminating a solution stream containing EGO and metal salt (e.g., H2PtCl6 or
RuCl3) with a 248 nm wavelength laser produces reduced EGO (rEGO, oxygen
content 4.0 at%) flakes, decorated with Pt (~2.0 nm) or RuO2 (~2.8 nm)
nanoparticles. The RuO2-rEGO flakes exhibit superior catalytic activity for the
oxygen evolution reaction, requiring a small overpotential of 225 mV to reach a
current density of 10 mA cm-2. The Pt-rEGO flakes (10.2 wt% of Pt) show
enhanced mass activity for the hydrogen evolution reaction, and similar
performance for oxygen reduction reaction compared to a commercial 20 wt% Pt/C
catalyst. This simple production method is also used to deposit PtPd alloy and
MnOx nanoparticles on rEGO, demonstrating its versatility in synthesizing
functional nanoparticle-modified graphene materials.
