Electrochemical CO2 reduction to multicarbon products faces challenges of unsatisfactory selectivity, productivity, and long-term stability. Herein, we demonstrate CO2 electroreduction in strongly acidic electrolyte (pH ≤ 1) on electrochemically reduced porous Cu nanosheets by combining the confinement effect and cation effect to synergistically modulate the local microenvironment. A Faradaic efficiency of 83.7 ± 1.4% and partial current density of 0.56 ± 0.02 A cm−2, single-pass carbon efficiency of 54.4%, and stable electrolysis of 30 h in a flow cell are demonstrated for multicarbon products in a strongly acidic aqueous electrolyte consisting of sulfuric acid and KCl with pH ≤ 1. Mechanistically, the accumulated species (e.g., K+ and OH−) on the Helmholtz plane account for the selectivity and activity toward multicarbon products by kinetically reducing the proton coverage and thermodynamically favoring the CO2 conversion. We find that the K+ cations facilitate C-C coupling through local interaction between K+ and the key intermediate *OCCO.

No abstract

The electrocatalytic nitrogen reduction reaction (NRR) for NH 3 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 N 2 diffusion on the NRR selectivity and activity.The EDL, as the immediate reaction environment, remarkably impedes the diffusion of N 2 to the cathode surface at high electrode potentials, which explains experimental observations. This article also gives microscopic insights into the interplay between N 2 diffusion and reaction activity under the nano-confinement, providing theoretical guidance for future design of advanced NRR electrocatalytic systems.

Due to the complexity of thermal effects in porous electrodes, the process of temperature rise in supercapacitors is difficult to be quantified by some simple but physically meaningful formulas. Here, the stack-electrode model is applied to investigate this issue both analytically and numerically. The numerical results show the process has three relaxation times, which divide that into four stages controlled by heat generation (HG) or heat transfer (HT). Temperature rise is first controlled by HG in the bulk phase, then by HG in both porous electrodes and bulk phase, then mainly by HT, and finally all by HT. The analytical formulas of three relaxation times and temperature rise under different structural parameters and intensity of heat dissipation are obtained. These formulas are expected to indicate the contribution of the different stages to total temperature rise, thus to guide the design of cooling methods of supercapacitors during the different stages.

Selective electroreduction of carbon dioxide (CO 2 RR) into ethanol at an industrially relevant current density is highly desired. However, it is challenging because the competing ethylene production pathway is generally more thermodynamically favored. Herein, we achieve a selective and productive ethanol production over a porous CuO catalyst that presents a high ethanol Faradaic efficiency (FE) of 44.1 ± 1.0% and an ethanol-to-ethylene ratio of 1.2 at a large ethanol partial current density of 501.0 ± 15.0 mA cm −2 , in addition to an extraordinary FE of 90.6 ± 3.4% for multicarbon products. Intriguingly, we found a volcano-shaped relationship between ethanol selectivity and nanocavity size of porous CuO catalyst in the range of 0 to 20 nm. Mechanistic studies indicate that the increased coverage of surface-bounded hydroxyl species (*OH) associated with the nanocavity size-dependent confinement effect contributes to the remarkable ethanol selectivity, which preferentially favors the *CHCOH hydrogenation to *CHCHOH (ethanol pathway) via yielding the noncovalent interaction. Our findings provide insights in favoring the ethanol formation pathway, which paves the path toward rational design of ethanol-oriented catalysts.

Developing efficient electrocatalysts for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) is crucial for various sustainable energy devices like rechargeable Zn-air batteries. Phase engineering has been proven to...

No abstract

Ion transport through nanoporous materials is of fundamental importance for the design and development of filtration membranes, electrocatalysts, and electrochemical devices. Recent experiments have shown that ion transport across porous materials is substantially different from that in individual pores. Here, we report a new theoretical framework for ion transport in porous materials by combining molecular dynamics (MD) simulations at nanopore levels with the effective medium approximation to include pore network properties. The ion transport is enhanced with the combination of strong confinement and dominating surface properties at the nanoscale. We find that the overlap of electric double layers and ion–water interaction have significant effects on the ionic distribution, flux, and conductance of electrolytes. We further evaluate the gap between individual nanopores and complex pore networks, focusing on pore size distribution and pore connectivity. This article highlights unique mechanisms of ion transport in porous materials important for practical applications.