Potential Effects on the Catalytic Mechanisms of OER and ORR

Abstract

A fundamental understanding of the catalytic mechanisms of the oxygen evolution reaction (OER) and the oxygen reduction reaction (ORR) at applied electrode potentials is crucial for designing bifunctional catalysts. Here, we revisit the OER and ORR on single-atom catalysts (SACs) by using the grand canonical fixed-potential method. It is revealed that the charge states of reaction intermediates are linearly related to the potential through the capacitance and surface area, and different intermediates exhibit different charge states under the same potential, which arises from the adsorption-induced change in the work function and surface dipole. As a result, the charge transfer in each proton-coupled electron-transfer step is no longer 1e − , yielding a deviation of the potential-dependent relative free energy from the simple expression with a linear potential correction as in the conventional computational hydrogen electrode model, further affecting the evaluation of overpotential and catalytic activity. Importantly, the slopes of universal scaling relations decrease linearly with increasing electrode potential, resulting in distinct scaling relationships for the OER and ORR. These findings highlight the key role of the potential effects on the OER/ORR and update the understanding of the catalytic mechanisms and catalytic activity trends under working potential.

Bidirectional electron transfer boosts Li–CO2 electrochemistry

“…6d displays the relationship between energies and electrode potentials, which follows a quadratic function, consistent with the logical progression of as introduced in calculation methods. 51,52 The fitted parameters of capacitance ( C ), potential of zero charge (PZC), and system energy at PZC are summarized in Tables S5 and S6 †. It is seen that for Fe/Ti 17 B 18 , the surface area normalized capacitance C was fitted to be 12.13 μF cm −2 , while it was 12.33 μF cm −2 for the pristine TiB monolayer (expecting further experimental verification).…”

“…Note that a Li redox electrode (Li + + e − → Li) was taken as a reference electrode at an experimental potential of −1.39 V vs. the vacuum potential level, as shown in Fig. S1,† taken from previous work of Trasatti and Gao et al 50,51 In principle, the relationship between energy E and potential U q satisfies a quadratic function based on double electric layer theory, as expressed below 51,52 …”

Density Functional Theory Study of Single-Atom Transition Metal Catalysts Supported on Pyridine-Substituted Graphene Nanosheets for Oxygen Reduction Reaction

“…To analyze the ORR, we employed the widely accepted Norskov methodology . After considering different methodologies, such as the constant potential method proposed by Henkelman group, we ultimately chose Norskov’s approach due to its extensive use in studying the ORR. − In our investigation, we studied the ORR by incorporating an O 2 molecule into the TM–N 4 V 2 structure (referred to as O 2 @TM–N 4 V 2 ). Subsequently, we systematically introduced H atoms to elucidate the effects of TM on the ORR.…”

Recent Progress and Prospects of Manganese–Nitrogen–Carbon Electrocatalysts for Oxygen Reduction Reaction

“…Energy serves as the fundamental cornerstone of human progress and development . The continuous growth of the population is accompanied by an increase in energy demands. − Nevertheless, the dependence on conventional fossil fuels has led to escalating environmental pollution, encompassing global warming and rising sea levels due to increased carbon dioxide emissions. − Consequently, current research focuses on developing economical and effective technologies for innovative approaches to clean energy conversion and storage, such as water decomposition, metal-air batteries, hydrogen storage and fuel cells. − In metal-air batteries and proton exchange membrane fuel cells, oxygen reduction reaction (ORR), as an important chemical reaction, usually restricts their actual performance. , The ORR generally proceeds through a 4-electron (4e – ) pathway and displays sluggish kinetics, which results in high energy barriers for the reaction. ,− Therefore, it is imperative to advance the development of exceptional electrocatalysts to accelerate the electrochemical ORR kinetics. − Presently, the common commercial catalysts predominantly composed of Pt demonstrate high catalytic performance. , However, the substantial cost of Pt-based catalysts makes them unsuitable to meet future market demands. − Hence, there is an urgent need to explore nonplatinum group (NPG) catalysts with efficient and high performances to reduce the independence of expensive Pt-based materials. − …”