Mastering the Electrified Interface Microenvironment for Selective Electrocatalysis

Conspectus Electrocatalysis plays a central role in sustainable energy conversion and chemical synthesis. However, practical efficiency is often limited by side reactions and mass transport constraints arising from poorly controlled electrode–electrolyte interfaces. While conventional approaches focus on optimizing intrinsic catalyst activity through composition and morphology, they frequently overlook the interfacial microenvironment, which critically governs reaction selectivity and kinetics. Our work is guided by a core principle: rational electrocatalyst design must be integrated with deliberate engineering of the interfacial microenvironment. Early experimental observations revealed that seemingly identical catalysts exhibit significantly different electrocatalytic performances under slightly altered electrolyte conditions. This phenomenon is attributed to changes in proton reactivity, ion distribution, and solvent structure at the interface following modifications of electrolyte composition. These insights have led us to advocate for a shift from static, catalyst-centric optimization toward dynamic regulation that takes into account the effects of the electrolyte. This Account combines our recent contributions with key advances from the field, focusing on three representative reactions: CO 2 reduction (CO 2 RR), oxygen reduction (ORR), and organic hydrogenation. A recurring theme is that effective microenvironment control operates across multiple spatial and temporal scales. We categorize direct interactions between isolated ions/solvents as short-range interactions, such as noncovalent ion–intermediate coordination, anion–H 2 O hydrogen bonding, and organic solvent molecule–H 2 O hydrogen bonding. These short-range interactions directly influence the stability of the reaction intermediates or participate in proton-coupled processes. On a larger scale, long-range effects (which are more akin to the cumulative effect of various short-range interactions) include interfacial pH gradients, electric field distributions, and hydrophilicity/hydrophobicity. Such long-range effects determine the concentration profiles of reactants or protons. To establish causal links between the designed interfacial modifications and catalytic outcomes, we use a combined approach of operando characterization and multiscale simulation. This includes in situ vibrational spectroscopy, electrochemical impedance, density functional theory (DFT), and ab initio molecular dynamics (AIMD) to visualize and quantify the dynamic, structural, chemical, and transport evolution of the interface under working conditions. Through systematic case studies, we demonstrate how electrolyte components can be utilized to reshape the interfacial microenvironment. The systems under investigation include alkali and organic cations, functional anions, organic cosolvents, surfactants, and polymers, which influence electrocatalytic reactions through direct electrode modification or adjustment of the solvent environment on the electrolyte side. These strategies enable the rational design of matched catalyst–electrolyte pairs that selectively promote desired proton-coupled electron transfer (PCET) pathways, steering selectivity toward valuable products (e.g., CO from CO 2, H 2 O 2 from O 2 ) while suppressing competing reactions. By emphasizing that mastering the stage (interface) is as important as designing the actor (catalyst), we aim to advance a mechanism-driven framework for next-generation electrochemical systems. We hope this perspective encourages more integrated strategies, accelerating progress toward carbon-neutral energy and sustainable synthesis.