CO2 diffusion is the rate-determining step for electrochemical CO2 reduction at large current densities. Herein, we develop a microfluidic spectroelectrochemical approach to measure the diffusion coefficients of CO2 in bicarbonates in operando for the first time. Our results establish the critical role of cation-affected electrolyte chemistry on the measured CO2 concentration profiles, which leads to erroneous measurements of CO2 diffusion coefficients in electrolytes during the reaction. After isolating the effect of cations using crown ethers, we find that CO2 diffusion follows the classical theory. With our approach, we quantify that the HCO3-/CO2(aq) equilibrium constant can be modulated by more than 3 orders of magnitude under electrolysis conditions. From these results, we further generalize the potential-dependent mechanisms of CO2 supply to the electrode. The local CO2 supply is dominated by CO2 diffusion in the weak steric effect regime and by the HCO3-/CO2(aq) equilibrium reaction in the strong steric effect regime.

X-to-chemical energy conversion efficiency (XTC efficiency, where X refers to thermal, electrical, and solar, etc., as well as the combinations of more than one of them) is an important metric for comparisons between various technologies in the chemical sector, so its definition is fundamental. However, conceptual issues still exist in the definition. Here, we establish a unified definition and apply it in the fields of thermo- and electrochemistry where conventional definitions vary. Particularly, this unified definition can delineate the energy level of the input energies. We further propose the concept of thermodynamics ideality, defined as the ratio of measured XTC efficiency to the corresponding thermodynamic limit; it tells the potential for improvement of chemical systems. This Viewpoint thus encourages the communities to report XTC efficiency using our established definition, to report thermodynamics ideality alongside, and to turn their attention to the investigations in the thermodynamic limit for cutting-edge chemical technologies.

We shed light, using an exergy balance model, on limiting efficiency, underlying mechanisms, current status and prospective directions for photothermal catalysis, which particularly is not a simple summation of photo- and thermo-catalysis.

In our proposed structure, a self-similar chain of metal nanoparticles (NPs) with gradually shrinking size and interspace distance was incorporated within the active layer of a perovskite solar cell (PSC), and critical parameters were identified. By leveraging localized surface plasmon resonance modes, the electric field within the host medium was amplified up to 18-fold between the metal NPs at the surface of the smallest nanoparticle. To achieve a broad range of incident and polarization angles, the chain model symmetrically was combined and coated with a thin layer, which exhibits symmetry along both the Z and X axes. The results indicate a substantial improvement in short-circuit current, increasing from 22.8 mA to 27.5 mA, representing a 20.6

To respond to the goal of "carbon peaking and carbon neutrality", this paper establishes a multiphysics macroscopic model of a flow electrolyzer based on a gas diffusion electrode in the context of electrocatalytic CO2 reduction and combines the established microscopic model of Ag-based catalytic surface density function theory and mesoscopic model of transition state theory to realize the multiscale coupling of electroreduction of CO2 in a flow electrolyzer. The experimental system of CO2 reduction in a flow electrolyzer is designed and built to verify the reliability of the theoretical calculations. In the range designed by the model, the CO faradaic efficiency is maintained at a high level, and the CO2 conversion increases rapidly with the increase of the cell voltage; the coverage of intermediates *CO2δ- and **COOH increases continuously with the rise of the cell voltage, and the coverage of *CO intermediates decreases continuously, which indicate that the increase of CO production leads to the rise of CO2 conversion; the excessive inlet flow rate leads to the rapid dilution of CO2; the rise of inlet CO2 concentration significantly enhances the reduction reaction rate, but the relatively higher CO2 concentration in the gas channel leads to a decrease in the conversion. The optimal operating parameters are: flow rate of 5 to 10 sccm, cell voltage of 2.8 V to 3.2 V, and inlet CO2 molar fraction of 10% to 20%, where the CO2 conversion and CO faradaic efficiency can exceed 10% and 90%, respectively.

Plasmonic photocatalysts provide means to efficient solar water splitting.Recently, researchers proposed that high-energy hot carriers generated by plasmon resonance can be transferred directly to the adsorbates, driving photochemistry, which differs from the previous indirect charge transfer forming electronhole pairs.This study analysed underlying mechanism of charge transition channel in plasmon-driven photochemistry at the atomic scale, and evidence was provided for distinguishing between different modes of charge transfer.A specific example, where a cluster of six gold atoms interacts with one water molecule, was investigated.Based on combined density functional theory (DFT), Linear-Response time-dependent density functional (LR-TDDFT) and Ehrenfest dynamics simulations, the results revealed that hot electrons selectively transfer to high-energy unoccupied orbitals through indirect single-particle excitations or direct plasmon decay excitations.Direct transition was more conducive to photochemical reactions due to its higher energy.

The photoelectrochemical redox battery (PRB) has been regarded as an alternative candidate for large-scale solar energy capture, conversion, and storage as it combines the superior advantages of photoelectrochemical devices and redox batteries. As an emerging solar energy utilization technology, significant progress has been made towards promoting and proliferating the practical applications of PRBs. However, wide market penetration of PRBs is still being significantly inhibited by limited photocatalytic activity, low efficiency, among other critical issues. Furthermore, the integration of each component, including solar materials, redox couples, and membranes and their interaction in PRBs play vital roles towards achieving smooth operation and high performance. Herein, the materials, mechanisms, recent advances, and challenges in the use of PRBs are presented. The crucial influence of redox couples, photoelectrode materials, membranes on the performance of the system including how they affect solar energy capture, reaction kinetics, and internal losses are systematically discussed. In addition, the recent advances of a single-battery of photoelectrode mode and an integrated device of solar cell mode are summarized. Furthermore, the state of the art performance of PRBs and their upscaling progress are also discussed. Finally, the challenges and perspectives for the future development of PRBs are highlighted.

Electrochemical CO2 reduction reaction (CO2RR) involves complicated processes spanning multiple scales, so understanding their effects on device performance is highly desired.Here, we present a multiscale strategy to predict the performance of an Ag-based H-type cell.The multiscale model consists of 1-D macro model, microkinetic model, and density functional theory (DFT) model.Free energy and barriers for CO2RR and hydrogen evolution reaction (HER) over Ag(111) surface are first obtained from the DFT model.These energy values are then used to determine the reaction rates for CO2RR and HER in the microkinetic model.These reaction rate values are finally imported into the macro model containing aqueous species.Using this multiscale model, we predicted the distribution of products and the partial current densities.We also described how factors such as CO2 coverage, the adsorption energy of H2O, and cathodic voltage affect electrochemical performance.Simulations under different CO2 pressures are being implemented, which is of great significance for understanding the mechanism of high-pressure electrochemical reduction of CO2.The investigation of electrochemical CO2RR presented in this work is helpful for the rational design of a high-performance CO2RR system.