Dynamic Tuning of a Thin Film Electrocatalyst by Tensile Strain

Abstract

We report the ability to tune the catalytic activities for the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) by applying mechanical stress on a highly n-type doped rutile TiO2 films. We demonstrate through operando electrochemical experiments that the low HER activity of TiO2 can reversibly approach those of the state-of-the-art non-precious metal catalysts when the TiO2 is under tensile strain. At 3% tensile strain, the HER overpotential required to generate a current density of 1 mA/cm2 shifts anodically by 260 mV to give an onset potential of 125 mV, representing a drastic reduction in the kinetic overpotential. A similar albeit smaller cathodic shift in the OER overpotential is observed when tensile strain is applied to TiO2. Results suggest that significant improvements in HER and OER activities with tensile strain are due to an increase in concentration of surface active sites and a decrease in kinetic and thermodynamics barriers along the reaction pathway(s). Our results highlight that strain applied to TiO2 by precisely controlled and incrementally increasing (i.e. dynamic) tensile stress is an effective tool for dynamically tuning the electrocatalytic properties of HER and OER electrocatalysts relative to their activities under static conditions.

Nanoscale Design of Pd‐Based Electrocatalysts for Oxygen Reduction Reaction Enhancement in Alkaline Media

“…This could weaken the binding affinity of oxygen species to the surface atoms and accelerate the overall reaction rate. [147][148][149][150][151] Such ORR activity improvement on a tensile-strained surface was claimed by Huang and coworkers using a unique class of PdÀPb@Pd core-shell nanosheets and nanocubes that they constructed with tensile strain on the (100) of both the top-Pd and the edge-Pd surfaces. [152] The mass activities of the resultant Figure 5.…”

Strain Influences the Hydrogen Evolution Activity and Absorption Capacity of Palladium

“…[3,8] We instead elected to use mechanical force to stretch polymer-supported palladium thin films to induce strain throughout the bulk of the electrode.External force was delivered to the 50 nm-thick palladium film using af lexible polymer support that was mechanically stretched. This method of stretching af lexible substrate with a1 0-50 nm layer of metal electrocatalyst on the surface has been used to correlate activity to strain for various electrochemical reactions (e.g., HER, [18][19][20][21][22] OER, [17] ORR [23][24][25][26] and others [27][28][29][30] ), but not for HER at ap alladium electrode.…”

Multiple Reaction Pathways for the Oxygen Evolution Reaction May Contribute to IrO2 (110)’s High Activity

“…9,55,56 In general, the relative differences in energy between reaction steps of adsorbed species are less at room temperature than the energy differences reported here, when including vibrational contributions to the zero point energy and the entropy. Likewise, the trends observed in adsorption energy will also typically correspond to adsorption free energies at moderate temperatures of ∼300 K. 57 We attempt to consider thermal effects by utilizing statistical mechanical arguments related to the Boltzmann populations of various isomers at the room temperature of 300 K: This a simplifying approximation, which does not include the stability and dynamics of hydrogen-bonding networks of the solvent, the potential gradient, or the possible chemical-Coulombic effects of electrolyte ions. However, the incorporation of these effects across dozens of isomers is non-trivial to compute.…”