The role of mechanical force on the kinetics and dynamics of electrochemical redox reactions on graphene

Abstract

Electrochemical reactions are a critical class of processes strongly influenced by atomic scale effects, where the relationships between local chemical composition, stress, strain, and reactivity are not well understood. Here we investigate the relationship between applied stress and reaction rates for the oxygen evolution reaction on multi-layered graphene using conductive atomic force microscopy. During the reaction, oxygen groups accumulate on the surface and the oxygenation rate increases with applied load. The results also show that the rate is not uniform across the surface, where local edges and defects are more reactive than the basal plane. The results presented here are interpreted in the context of transition state theory, where applied load over the reaction coordinate linearly modifies the energy landscape. This work motivates the general efficacy of atomic force microscopy as a tool to study relationships between local mechanical surface effects and electrochemical reactivity.

Dynamic Tuning of a Thin Film Electrocatalyst by Tensile Strain

“…Examples of tunable substrates include elastic materials such as organic polymers 16–21 and metallic materials such as stainless steel 22 and pseudoelastic/shape-memory NiTi alloys 23,24 . Alternatively, external forces have been applied by an atomic force microscopy tip 25 , by introducing subsurface inert gas bubbles 26–28 or by Li-ion intercalation/deintercalation in battery materials 6,29–31 . Application of mechanical, thermal or electrical loading result in bending, compression or expansion of an elastic substrate, further inducing stress-strain response on the deposited material.…”

Kinetics of primary mechanochemical covalent-bond-forming reactions

“…Tip-induced force has also been used in combination with other stimuli, such as heat, 105 electrical potential, 140 and light 141 to study CBF reactions on surfaces, and these efforts have helped explain how mechanical energy operates within the complex energy landscape of CBF reactions. For example, Raghuraman et al studied the relationship between applied mechanical force and applied voltage on the rate of oxygenation of multilayered graphene using conductive AFM probes.…”

“…For example, Raghuraman et al studied the relationship between applied mechanical force and applied voltage on the rate of oxygenation of multilayered graphene using conductive AFM probes. 140 The reaction was monitored by tracking changes in the friction of the surface, which increased in oxygenated areas relative to unmodified graphene (Fig. 12A).…”