A Universal Approach to Quantify Overpotential-Dependent Selectivity Trends for the Competing Oxygen Evolution and Peroxide Formation Reactions: A Case Study on Graphene Model Electrodes

Abstract

In this article, we study the competing oxygen evolution and hydrogen peroxide (H 2 O 2 ) formation reactions for periodic models of graphene with different active-site concentrations by means of density functional theory (DFT) calculations. Linking the DFT calculations to ab-initio thermodynamic considerations in conjunction with microkinetic modeling enables gaining deep insights into the activity and selectivity trends of graphene-based electrodes as a function of applied bias. We illustrate that both the coverage of intermediates on the electrode surface and the applied electrode potential have a significant effect on the Faradaic efficiency for the electrocatalytic production of H 2 O 2 . The presented approach to study overpotential-dependent selectivity trends allows deriving design criteria for peroxide formation, which may serve as a guideline for further studies to realize selective formation of H 2 O 2 using carbon-based materials.

Method to Determine the Bifunctional Index for the Oxygen Electrocatalysis from Theory

“…One might argue that the usage of adsorption free energies to model the reaction kinetics is an oversimplification of a complex problem. However, we would like to emphasize that the BEP relation has been justified in previous works, [54,55] and the usage of adsorption free energies rather than transition states (kinetics) enables application of our approach for a data-driven screening of the BI, which is in the foreground of this manuscript. In summary, eq.…”

“…Figure 2). As discussed in previous works of Exner, there is an internal Brønsted-Evans-Polanyi (BEP) relation [54] between the rds and the overpotentialdependent descriptor G max h ð Þ, [24,49,55] which reads:…”

Nanoparticle-Assisted Ni–Co Binary Single-Atom Catalysts Supported on Carbon Nanotubes for Efficient Electroreduction of CO2 to Syngas with Controllable CO/H2 Ratios

“…The reaction activity and selectivity toward competing products can be evaluated by the Gibbs free-energy change and binding energy from the perspective of thermodynamics. 36,37 Ni−N 4 and Co−N 4 are adopted as representative structures of single-atom sites on CNTs (Figure 6a,b), according to reported literature studies. 38,39 The reactivity toward CO 2 RR and HER can be reflected in the binding energy of the key intermediates *CO and *H, respectively.…”

“…DFT calculations were performed to get insight into the electrocatalytic mechanism of single-atom sites and NPs. The reaction activity and selectivity toward competing products can be evaluated by the Gibbs free-energy change and binding energy from the perspective of thermodynamics. , Ni–N 4 and Co–N 4 are adopted as representative structures of single-atom sites on CNTs (Figure a,b), according to reported literature studies. , The reactivity toward CO 2 RR and HER can be reflected in the binding energy of the key intermediates *CO and *H, respectively. The Ni–N 4 -CNT structure was calculated to have a positive binding energy of *CO (0.34 eV), while Co–N 4 -CNT, Ni(111), and Co(111) models present negative binding energies (Figure c), which suggests that the desorption of CO is more easi to occur on Ni–N 4 -CNT.…”

Mo3(C6O6)2 monolayer as a promising electrocatalyst for the CO2 reduction reaction: a first-principles study

“…The transition from the reaction intermediate with the lowest free energy to the reaction intermediate with the highest free energy in the free energy diagram is described using G max . 55–57 The difference between the G max values of the CRR and hydrogen evolution reaction (HER) is used to estimate the selectivity of the catalyst, which is expressed as: G sel = G max(HER) − G max(CRR) …”