In electrocatalytic reactions, reactants react with the electrode surface and the catalyst existing on the surface of the electrode or in the solution can promote or inhibit the electron transfer reaction under the action of an electric field, while the catalyst itself does not change. Explaining the catalytic mechanism is of vital importance and the main goal is to find the optimal electrocatalysts and best conditions to perform the desired reactions with the highest efficiency. Theoretical calculations based on quantum chemistry are widely used to study various thermodynamic parameters of reactions in electrocatalytic reaction mechanism research.
Electrocatalytic Reactions
Oxygen evolution reaction and the hydrogen evolution reaction are two major electrocatalytic reactions taking place in the electrodes of a cell are the , which have been largely studied.
Figure 1. The oxygen evolution reaction (OER) mechanism in acid (blue line) and alkaline (red line) medium. (Zhong, H.H.; et al.)
- Oxygen evolution reaction (OER)
OER is a four-electron transfer process. In an OER process, the catalyst adsorbs the reactant on the surface to form an adsorption intermediate, thereby promoting the charge transfer between the electrode and the reactant. Various electrocatalytic kinetic parameters such as overpotential, exchange current density, and Tafel slope of the OER electrocatalyst can be used to calculate and predict the performance of the electrocatalytic reactions mechanism.
- Hydrogen evolution reaction (HER)
The HER takes place at the cathode, in which a hydrogen ion gets two electrons to produce hydrogen. The basic mechanism of HER is that protons obtain electrons to form adsorbed hydrogen atoms on the surface of the catalyst, and then they further combine with protons in the electrolyte. Finally, hydrogen evolution reaction and a composite desorption process occur.
Our services
Alfa Chemistry provides accurate electrocatalytic reaction mechanism calculation approaches including the density functional theory, quantum mechanics based method, non-equilibrium surface Green's function methodology. Our fast and high-quality services include the following:
- Density functional theory
We use a first principles-based density functional theory and periodic plate model to calculate the atomic and electronic structure of the electrode surface. Our scientists carry out an in-depth study on the adsorption process and electrocatalytic oxidation mechanism of small molecules, as well as discuss the electrode surface Internal relations between structure, adsorption, electrocatalysis and other properties. Combing the knowledge of solid-state physics and electrochemical theory, our experts construct a physical model of the electrode by changing the charge of the metal state surface model and simulating the electrode potential movement, and calculate the electrochemical characteristics of the electrode surface.
- Quantum mechanics based method
We introduce the quantum mechanics based multiscale simulations to identify the reaction mechanisms and use in silico methods to predict the best modifications to improve performance of electrocatalysts. Our well-designed quantum mechanics based molecular simulation metadynamics at the standard PBE-D3 level of DFT allow us to determine the fundamental reaction mechanisms and kinetics on low index surfaces of electrocatalysts.
- Non-equilibrium surface Green's function methodology (surface NEGF)
At Alfa Chemistry, we apply the non-equilibrium surface Green's function methodology to simulate the surface structure under an external electric field. The surface NEGF method takes into account the charge transfer effects, ensuring that adsorbed species may be charged with charges from the bulk electrode region without changing the chemical potential of the surface. Our NEGF method can therefore provide precise studies of mechanisms of electrocatalytic reactions on surfaces.
Advantages of Our Services
- Based on DFT calculations, we establish the relationship between the activation free energy of all the elementary reaction steps of the HER/HOR reaction on the electrode surface and the potential.
- In terms of the study of liquid-phase electrocatalytic reactions, our experts can calculate voltage, current density, Faraday efficiency, Gibbs free energy correlation. We are also capable of building solid-liquid interface electrical double layer and proton-electron pair models, in which the effect of temperature, concentration, pH and other reaction conditions are fully considered.
- Our computational simulation of the electron transfer process at the electrode−electrolyte interface can help to elucidate the accurate electrocatalytic reaction mechanism of electrocatalysts while overcoming the difficulties faced by the in vivo spectroscopic analysis.
Alfa Chemistry provides high-quality electrocatalytic reaction mechanism calculation services for our customers. Our capabilities include the density functional theory, quantum mechanics based method, non-equilibrium surface Green's function methodology. We help to study the reaction results and mechanisms for your innovative scientific research. If you have any questions, please feel free to contact us.
Reference
- Zhong, H.H.; et al. Recent Advances of Cobalt-Based Electrocatalysts for Oxygen Electrode Reactions and Hydrogen Evolution Reaction. Catalysts. 2018, 8, 559.