Observation of an Inverse Kinetic Isotope Effect in Oxygen Evolution Electrochemistry

Abstract

Earth-abundant and inexpensive catalysts with low overpotential and high durability are central to the development of efficient water splitting electrolyzers. However, improvements in catalyst design and preparation are currently hampered by the lack of detailed understanding of the reaction mechanisms of the oxygen evolution reaction (OER) facilitated by non-precious metal (NPM) catalysts. In this manuscript, we conducted a kinetic isotope effect (KIE) study in an effort to identify the rate-determining step (RDS) of these intricate electrocatalytic reactions involving multiple proton-coupled electron transfer (PCET) processes. We observed an inverse KIE for OER catalyzed by Ni and Co electrodes. These results contribute to a more complete understanding of the OER mechanism and allow for the future development of improved NPM catalysts.

Oxygen Evolution Reaction at Carbon Edge Sites: Investigation of Activity Evolution and Structure–Function Relationships with Polycyclic Aromatic Hydrocarbons

“…Thek inetic isotope effect (KIE) is an effective experimental technique to study chemical reactions involving protons. [13] As displayed in Figure 3a,t he OER activity decreases significantly when the OER is operated in aK OH/D 2 Om edium. TheT afel slopes also increase from 66 mV dec À1 in protic solution to 81 mV dec À1 in deuterated solution (Figure 3b), which indicates there is ad ifference in the Gibbs free energy of the intermediate that affects the reaction rate.…”

Direct oxygen isotope effect identifies the rate-determining step of electrocatalytic OER at an oxidic surface

“…Second, 18 O KIEs have mostly been determined via density measurements 41 , 42 , later via mass spectrometric analysis of CO 2 after combustion 43 and rarely on the O 2 molecule itself. Third, isotopic labelling as usually performed for the determination of 2 H KIEs, is significantly less feasible as commercial sources are expensive 46 .…”

Nature-inspired electrocatalysts and devices for energy conversion

“…230 Hence, extensive research is conducted on the synthesis and design of efficient and cost-effective electrocatalysts based on transition metals and layered double hydroxide materials. 213,[231][232][233][234][235][236][237][238][239][240][241][242][243][244] The design of new electrocatalysts for OER is focused on three scale levels: (i) at the atomic scale, the alteration of oxidation state, 245 coordination, 246,247 electron density, 245 and composition of metal composites 245,248 leads to an improvement of their electronic structure and an increase in OER activity; (ii) at the nano-scale, different material combinations (such as metal oxides), 249,250 chalcogenide, 249 boride, 251 nitride, 252 phosphide 250 supported on nanostructures (e.g. nanowires, 253,254 nanosheets, 251,254 nanotubes 255,256 ) have increased activity toward OER due to their high surface area and number of active sites; and (iii) at the meso-scale, the creation of a porous architecture of the support can enhance mass transport of the electrolyte, improving the activity and conductivity of the electrocatalyst.…”