Laser Assisted Solution Synthesis of High Performance Graphene Supported Electrocatalysts

Abstract

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, we report a laser-assisted, continuous, solution route for the simultaneous reduction and modification of graphene oxide with catalytic nanoparticles. Electrochemical graphene oxide (EGO) was 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 photo-degradation. Simply illuminating a solution stream containing EGO and metal salt (e.g. H2PtCl6 or RuCl3) with a 248 nm wavelength laser produced 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 exhibited 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) shows 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 was also used to deposit PtPd alloy and MnOx nanoparticles on rEGO, demonstrating its versatility in synthesizing functional nanoparticle-modified graphene materials.

Laser solid-phase synthesis of single-atom catalysts

“…Unlike other chemical and thermal reduction methods, laser reduction is characterized by energy absorption by the GO films dependent on the radiation wavelength and pulse width. From the wavelength perspective, the photoreduction of GO generally can be achieved photochemically with radiation wavelength in the UV region 36 and photothermally using radiation from visible to IR 37 . From the temporal perspective, the laser–matter interaction occurs in a clear time sequence 38 : excitation of an electron by incident photon occurs in the first ~100 fs, following by electron–phonon coupling from 100 fs to 10 ps, finally from 100 ps or longer heat dissipate to the surrounding matrix.…”

“…When the ps UV laser was applied, photochemical removal of functional groups was expected 42 . The photon energy of the 355 nm light is 3.49 eV can excite single-photon-mediated valence-to-conduction band transition of EGO (with a direct bandgap range from 3.25 to 3.95 eV) 36 , 43 . While for the 1064 nm beam at a photon energy of ~1.17 eV, multiphoton process is required to excite EGO.…”

“…S10 ) reached 803.7 K at the laser fluence of 2.0 mJ cm −2 and the number of pulses of ~404, suggesting that both photochemical and photothermal heating took place simultaneously. Since the UV laser (355 nm, ~4.86 eV) photon energy is far below the resonant excitation of C–O or C=O bond 22 , direct excitation may occur through valence-to-conduction band transitions, which may lead to ejection of plasma in the material 43 and/or photoreduction of EGO film by photon excited electrons of residual water molecules 22 or EGO itself 36 . As the direct ionization occurs ahead of thermal accumulation 43 , 44 , the photoreduction of the EGO could occur via combined mechanisms with the following sub-processes: (i) removal of oxygen-containing functional groups, (ii) conversion of reduced carbon sp 3 into sp 2 structure, and (iii) restoration of sp 2 network.…”

Laser Synthesis and Microfabrication of Micro/Nanostructured Materials Toward Energy Conversion and Storage

“…While the 1064 nm laser mainly induced vibration of water molecules, then the stretched OH groups of water molecules facilitated the hydrolysis reaction of metal ions and led to the formation of ([Ni 0.15 Mn 0.15 Co 0.7 (OH) 2 ](NO 3 ) 0.2 ·H 2 O) hydroxide nanostructures. Recently, Liu et al [ 135 ] reported a laser-assisted, continuous, solution route for the simultaneous reduction and modification of graphene oxide with Pt, PtPd alloys, RuO 2 and MnO x nanoparticles, which demonstrated the versatility of PLICN in synthesizing functional nanoparticle-modified graphene materials.…”

Advances in the Applications of Graphene-Based Nanocomposites in Clean Energy Materials

“…X-ray photoelectron spectroscopy (XPS) is mainly used to study the elements on the surface of materials and their different valence states. Peng et al [41] synthesized high-performance graphenesupported electrocatalysts by laser-assisted solution. The valence state characterization of Ru by XPS showed that Ru mainly existed in the Ru 4+ state, while Pt mainly existed in the Pt 0 form, and a small part was Pt 2+ .…”