A new operando surface restructuring pathway via ion-pairing of catalyst and electrolyte for water oxidation

The highly efficient and stable electrolysis needs the rational control of the catalytically active interface during the reactions. Here we report a new operando surface restructuring pathway activated by pairing catalyst and electrolyte ions. Using SrCoO3-δ-based perovskites as model catalysts, we unveil the critical role of matching the catalyst properties with the electrolyte conditions in modulating catalyst ion leaching and steering surface restructuring processes toward efficient oxygen evolution reaction catalysis in both pH-neutral and alkaline electrolytes. Our results regarding multiple perovskites show that the catalyst ion leaching is controlled by catalyst ion solubility and anions of the electrolyte. Only when the electrolyte cations are smaller than catalyst's leaching cations, the formation of an outer amorphous shell can be triggered via backfilling electrolyte cations into the cationic vacancy at the catalyst surface under electrochemical polarization. Consequently, the current density of reconstructed SrCoO3-δ is increased by 21 folds compared to the pristine SrCoO3-δ at 1.75 V vs. reversible hydrogen electrode and outperforms the benchmark IrO2 by 2.1 folds and most state-of-the-art electrocatalysts in the pH-neutral electrolyte. Our work could be a starting point to rationally control the electrocatalyst surface restructuring via matching the compositional chemistry of the catalyst with the electrolyte properties

Multiscale modeling of electrolytes in porous electrode: From equilibrium structure to non-equilibrium transport

Understanding the mechanisms and properties of various transport processes in the electrolyte, porous electrode, and at the interface between electrode and electrolyte plays a crucial role in guiding the improvement of electrolytes, materials and microstructures of electrode. Nanoscale equilibrium properties and nonequilibrium ion transport are substantially different to that in the bulk, which are difficult to observe from experiments directly. In this paper, we introduce equilibrium and no-equilibrium thermodynamics for electrolyte in porous electrodes or electrolyte–electrode interface. The equilibrium properties of electrical double layer (EDL) including the EDL structure and capacitance are discussed. In addition, classical non-equilibrium thermodynamic theory is introduced to help us understand the coupling effect of different transport processes. We also review the recent studies of nonequilibrium ion transport in porous electrode by molecular and continuum methods, among these methods, dynamic density functional theory (DDFT) shows tremendous potential as its high efficiency and high accuracy. Moreover, some opportunities for future development and application of the non-equilibrium thermodynamics in electrochemical system are prospected

Charging dynamics in a laminate-electrode model for graphene-based supercapacitors

Development of porous electrode materials for high-performance supercapacitors depends on the efficiency of pore utilization for charge storage. It remains an experimental and theoretical challenge to quantitatively relate the porous structure to charging dynamics. Here, based on a laminate-electrode model of graphene-based supercapacitors, we perform the equivalent circuit model to characterize the structure-charging dynamics relationship of porous electrodes by coupling key structural features in a mathematical expression for the Resistor-Capacitor (RC) time. This theoretical description is validated by direct numerical calculations of the Poisson-Nernst-Planck (PNP) equations. We discover that the charging dynamics of graphene-based supercapacitors is dominated by the ion diffusion from the electrolyte region into the layered structure. The predicted charging time compares well with the experimental investigations reported in the literature on graphene-based supercapacitors. Our work bridges nanoscopic transport behaviors with macroscopic devices, providing theoretical insights of the structure-dependent ion transport in two-dimensional materials-based films for compact energy storage

Enhancing electrocatalytic N-2 reduction via tailoring the electric double layers

The electrocatalytic nitrogen reduction reaction (NRR) for NH3 synthesis is still far from being practical and competitive with the common Haber–Bosch process. The rational design of highly selective NRR electrocatalyst is therefore urgently needed, which requires a deep understanding of both the electrode–electrolyte interface and the mass transport of reactants. Here, we develop a theoretical framework that includes electric double layer (EDL), mass transport, and the NRR kinetics. This allows us to evaluate the roles of near-electrode environment and N2 diffusion on the NRR selectivity and activity. The EDL, as the immediate reaction environment, remarkably impedes the diffusion of N2 to the cathode surface at high electrode potentials, which explains experimental observations. This article also gives microscopic insights into the interplay between N2 diffusion and reaction activity under the nano-confinement, providing theoretical guidance for future design of advanced NRR electrocatalytic systems

Enhancing electrocatalytic N-2 reduction via tailoring the electric double layers

The electrocatalytic nitrogen reduction reaction (NRR) for NH3 synthesis is still far from being practical and competitive with the common Haber–Bosch process. The rational design of highly selective NRR electrocatalyst is therefore urgently needed, which requires a deep understanding of both the electrode–electrolyte interface and the mass transport of reactants. Here, we develop a theoretical framework that includes electric double layer (EDL), mass transport, and the NRR kinetics. This allows us to evaluate the roles of near-electrode environment and N2 diffusion on the NRR selectivity and activity. The EDL, as the immediate reaction environment, remarkably impedes the diffusion of N2 to the cathode surface at high electrode potentials, which explains experimental observations. This article also gives microscopic insights into the interplay between N2 diffusion and reaction activity under the nano-confinement, providing theoretical guidance for future design of advanced NRR electrocatalytic systems

Multiscale modeling of electrolytes in porous electrode: From equilibrium structure to non-equilibrium transport

Understanding the mechanisms and properties of various transport processes in the electrolyte, porous electrode, and at the interface between electrode and electrolyte plays a crucial role in guiding the improvement of electrolytes, materials and microstructures of electrode. Nanoscale equilibrium properties and nonequilibrium ion transport are substantially different to that in the bulk, which are difficult to observe from experiments directly. In this paper, we introduce equilibrium and no-equilibrium thermodynamics for electrolyte in porous electrodes or electrolyte–electrode interface. The equilibrium properties of electrical double layer (EDL) including the EDL structure and capacitance are discussed. In addition, classical non-equilibrium thermodynamic theory is introduced to help us understand the coupling effect of different transport processes. We also review the recent studies of nonequilibrium ion transport in porous electrode by molecular and continuum methods, among these methods, dynamic density functional theory (DDFT) shows tremendous potential as its high efficiency and high accuracy. Moreover, some opportunities for future development and application of the non-equilibrium thermodynamics in electrochemical system are prospected

Enhancing electrocatalytic N-2 reduction via tailoring the electric double layers

The electrocatalytic nitrogen reduction reaction (NRR) for NH3 synthesis is still far from being practical and competitive with the common Haber–Bosch process. The rational design of highly selective NRR electrocatalyst is therefore urgently needed, which requires a deep understanding of both the electrode–electrolyte interface and the mass transport of reactants. Here, we develop a theoretical framework that includes electric double layer (EDL), mass transport, and the NRR kinetics. This allows us to evaluate the roles of near-electrode environment and N2 diffusion on the NRR selectivity and activity. The EDL, as the immediate reaction environment, remarkably impedes the diffusion of N2 to the cathode surface at high electrode potentials, which explains experimental observations. This article also gives microscopic insights into the interplay between N2 diffusion and reaction activity under the nano-confinement, providing theoretical guidance for future design of advanced NRR electrocatalytic systems