Robust Electrografting on Self-Organized 3D Graphene Electrodes

Abstract

Improving graphene-based electrode fabrication processes and developing robust methods for its functionalization are two key research routes to develop new high-performance electrodes for electrochemical applications. Here, a self-organized three-dimensional (3D) graphene electrode processed by pulsed laser deposition with thermal annealing is reported. This substrate shows great performance in electron transfer kinetics regarding ferrocene redox probes in solution. A robust electrografting strategy for covalently attaching a redox probe onto these graphene electrodes is also reported. The modification protocol consists of a combination of diazonium salt electrografting and click chemistry. An alkyne-terminated phenyl ring is first electrografted onto the self-organized 3D graphene electrode by in situ electrochemical reduction of 4-ethynylphenyl diazonium. Then the ethynylphenyl-modified surface efficiently reacts with the redox probe bearing a terminal azide moiety (2-azidoethyl ferrocene) by means of Cu(I)-catalyzed alkyne-azide cycloaddition. Our modification strategy applied to 3D graphene electrodes was analyzed by means of atomic force microscopy, scanning electron microscopy, Raman spectroscopy, cyclic voltammetry, and X-ray photoelectron spectroscopy (XPS). For XPS chemical surface analysis, special attention was paid to the distribution and chemical state of iron and nitrogen in order to highlight the functionalization of the graphene-based substrate by electrochemically grafting a ferrocene derivative. Dense grafting was observed, offering 4.9 × 10(-10) mol cm(-2) surface coverage and showing a stable signal over 22 days. The electrografting was performed in the form of multilayers, which offers higher ferrocene loading than a dense monolayer on a flat surface. This work opens highly promising perspectives for the development of self-organized 3D graphene electrodes with various sensing functionalities.

Nanoimpacts Reveal the Electron‐Transfer Kinetics of the Ferrocene/Ferrocenium Couple Immobilised on Graphene Nanoplatelets

“…Measurement of the half‐wave potential ( E 1/2 =+0.70 V) and formal potential ( =+0.35 V) from Figure yields the value for η 1/2 to be 0.35 V. Substitution of all known parameters gave k 0 =3±1 s −1 , which is consistent with prior literature estimations that range from 0.35 to 44 s −1 , either for direct charge transfer from ferrocene derivatives to carbon electrodes– or indirect charge transfer through multiwalled carbon nano‐ tubes . The value for k 0 was determined by assuming the absence of contact resistance between the particles and the electrode; hence, possible interference from contact resistance cannot be completely ruled out during nanoimpacts, and the value of 3±1 s −1 should be considered to be a lower limit for k 0 .…”

Pulsed Laser Deposited Films for Microbatteries

“…These films, however, were not used as electrodes. On the other hand, a N-doped graphene (NG) electrode prepared by PLD coupled with in-situ thermal annealing (PLD-TA) was achieved by Fortgang et al [338]. More recently, Bourquard et al used the PLD-TA process to form an N-doped graphene film by high temperature condensation of the laser-induced carbon plasma plume onto the Si electrode previously covered by an Ni catalytic film [339], using a protocol published by the same group [340] Carbon was ablated at 780 • C from the graphite target using a femtosecond laser (λ = 800 nm, pulse width of 60 ns, repetition rate of 1 kHz, and Φ = 5 J·cm −2 ) at a distance of 36 mm from the graphite target, with P N = 10 Pa in the vacuum chamber.…”

Progress in pulsed laser deposited two-dimensional layered materials for device applications

“…A similar method was applied to grow multi-layer, textured graphene films on n-doped Si substrate. 75 For the first step, an amorphous carbon film was deposited on a Ni layer buffered Si substrate using PLD. Subsequently, the graphene was converted from the carbon film using a post-annealing process.…”