Investigating The Influence Of Anions On The Electric Double Layer And Electrochemical PCET Reactions By Spectroelectrochemistry

Electrocatalytic reactions widely exist in many energy-related reactions,such as CO2 reduction,hydrogen evolution reaction,and methanol oxidation.Electrocatalytic reactions play a critical role in energy conversion and storage devices such as fuel cells,CO2 reduction.Broadly speaking,electrocatalysis is the study of electrode reactions whose kinetics strongly depend on the physicochemical properties of the electrochemical interface,including the properties of the electrode materials and the bilayer structure of the electrode surface.Altering the electrochemical interface by using the electrolyte effect or so-called "electrolyte engineering" provides a general approach to tune the electrochemical response.The proton-coupled electron transfer reaction(PCET)which exists in many electrocatalysis and electrosynthesis reactions can be controlled by adjusting the electrochemical interface structure by adjusting the hydrogen bond structure or solvent environment.Therefore,it is of great significance to deeply understand the electrolyte effect from the perspective of the interfacial properties of the electrode/electrolyte interface.This paper adopts the method of spectroelectrochemistry,mainly focuses on the influence of anions in the electrolyte solution on the bilayer structure and electrochemical PCET reaction,and explores the anion-interface interaction and the nature of the electrochemical PCET reaction adjusted by anions.The electrolyte-related structure-property relationships at the interface provide theoretical guidance.The work content and innovation points of this paper are mainly divided into the following two parts:1.Spectroscopic-electrochemical characterization of the special counter ion effect at the electrode-solution interface of the electrolyte commonly used in the four neutral electrochemical reaction systems was carried out by using surface-enhanced infrared absorption spectroscopy electrochemical technology combined with vibration Stark effect.Difference in distributions of anions as counter ions in the electric double layer due to the difference in the strength of the interaction with the electrode surface,and resultant different shielding of the local electric field at the interface is revealed through vibrational Stark probe with different molecular length.Anions that specifically interact with the electrode can be adsorbed in the Stern layer,significantly reducing the local effective electric field.This is of great significance for further understanding the structure of electrochemical double layer and the structure-activity relationship of electrocatalytic reaction.At the same time,we proposed an effective quantitative analysis method for analysis of electrode-electrolyte interface.2.We employ in situ surface-enhanced infrared spectroelectrochemistry and computational simulation to explore how kosmotropic and chaotropic anions regulate the hydrogen-bond environment in the electric double layer and their distinct effect on the proton-coupled electron transfer by using of 4-aminothiophenol(PATP)as a probe.We disclose that structure-making and structure-breaking anions greatly tune the ordering of water networks and the strength of hydrogen bond in a long range,and water with a long-range ordered tetrahedral structure could promote PCET during the electrochemical oxidation of PATP.This anion tuning strategies provides a general method for modulating water-assisted chemical reactions.