Formate-Selective CO2 Electrochemical Reduction with a Hydrogen-Reduction-Suppressing Bronze Alloy Hollow-Fiber Electrode

Engineering Flow-Through Hollow Fiber Gas-Diffusion Electrodes for Unlocking High-Rate Gas-Phase Electrochemical Conversion

Designing advanced electrodes with efficient contact with gas, electrolytes, and catalysts presents significant opportunities to enhance the accessibility of concentrated gas molecules to the catalytic sites while mitigating undesirable side reactions such as the hydrogen evolution reaction (HER), which advances the gas-phase electrochemical reduction toward industrial-scale applications. Traditional planar electrodes face challenges, including limited gas solubility and restricted mass transport. Although commercial flow-by gas-diffusion electrodes can reduce mass transfer resistance by enabling direct diffusion of gas molecules to active sites, the reliance on diffusive gas flow becomes insufficient to meet the rapid consumption demands of gas reactants at high current density. Flow-through hollow fiber gas-diffusion electrodes (HFGDEs) or hollow fiber gas penetration electrodes (HFGPEs) provide a promising solution by continuously delivering convective gas flow to active sites, resulting in enhanced mass transport and superior gas accessibility near the catalytic sites. Notably, HFGDEs have demonstrated the ability to achieve current densities exceeding multiple amperes per square centimeter in liquid electrolytes. This review provides a comprehensive overview of the design criteria, fabrication methods, and design strategies for porous metallic HFGDEs. It highlights the state-of-the-art advancements in HFGDEs composed of various metals (e.g., Cu, Ni, Ag, Bi, Ti, and Zn), with a particular focus on their utilization in the electrochemical conversion of CO2. Finally, future research directions are discussed, underscoring the potential of porous metallic HFGDEs as a versatile and scalable electrode architecture for diverse electrochemical applications.

The ZnO-SiO2 Composite Phase with Dual Regulation Function Enables Uniform Zn2+ Flux and Fast Zinc Deposition Kinetics Toward Zinc Metal Batteries

As an important candidate for rechargeable energy storage devices, the large-scale development of aqueous zinc ion batteries has been hindered by hydrogen evolution and uncontrollable dendrites of metal anodes. A novel ZnO-SiO2 composite interface phase (Zn@ZSCP) with a double protective effect based on in situ synthesis by hydrothermal method is used to improve these difficulties. The hydrophilic SiO2 layer is beneficial to the dissolution of hydrated zinc ions and reduces the nucleation barrier during zinc deposition, while the stable ZnO layer helps to adjust the electric field distribution on the surface of the metal anode to further induce uniform zinc nucleation. The cycle life of the Zn@ZSCP||Zn@ZSCP symmetric battery based on this innovative interface phase modification is up to 2500 h. Even at a high current density of 8 mA cm-2, the symmetric battery still has a stable cycle life of more than 2000 h. The zinc-iodine full battery based on Zn@ZSCP anode and low-cost biomass-derived porous carbon exhibits an excellent specific capacity and outstanding cycle stability. This simple and reasonable battery structure design not only improves the practicability of aqueous zinc ion batteries to a certain extent but also helps to develop more efficient and environmentally friendly zinc metal batteries.

CuBi electrocatalysts modulated to grow on derived copper foam for efficient CO2-to-formate conversion

Electrochemical reduction of CO₂ to fuels and chemicals is an effective way to reduce greenhouse gas emissions and alleviate the energy crisis, but the highly active catalysts necessary for this reaction under mild conditions are still rare. In this work, we grew CuBi bimetallic catalysts on derived copper foam substrates by co-electrodeposition, and then investigated the correlation between co-electrodeposition potential and electrochemical performance in CO₂-to-formate conversion. Results showed that the bimetallic catalyst formed at a low potential of - 0.6 V vs. AgCl/Ag electrode achieved the highest formate Faradaic efficiency (FE_formate) of 94.4% and a current density of 38.5 mA/cm² at a low potential of - 0.97 V vs. reversible hydrogen electrode (RHE). Moreover, a continuous-flow membrane electrode assembly reactor also enabled the catalyst to show better performance (a FE_formate of 98.3% at 56.6 mA/cm²) than a traditional H-type reaction cell. This work highlights the vital impact of co-electrodeposition potential on catalyst performance and provides a basis for the modulated growth of bimetallic catalysts on substrates. It also shows the possibility of preparing Bi-based catalysts with no obvious decrease in catalytic activity that have been partially replaced with more economic copper.

Highly efficient electrochemical reduction of carbon dioxide to formate on Sn modified Bi2O3 heterostructure

In this work, Sn species are deposited onto the surface of a Bi₂O₃ material by a facile disproportionated reaction and the prepared catalyst shows a superior electrocatalytic performance towards CO₂ reduction. The deposition of Sn atoms can donate electrons to the Bi₂O₃ material and increase its electrical conductivity. The Sn_M-Bi₂O₃ catalyst with the optimal Sn content delivers a high faradaic efficiency of 95.8% at -1.0 V for formate production. In addition, the partial current density of formate can reach 41.8 mA cm^-2. The Sn_M-Bi₂O₃ catalyst also exhibits superior stability towards long-term electrolysis. The modification of Sn species not only helps to stabilize the reaction intermediate but also inhibits the hydrogen evolution reaction (HER) pathway, achieving the synergetic enhancement of catalytic activity.

Hollow fibers: from fabrication to applications

Hollow fibers have attracted more and more attention due to their broad range of applications in numerous fields. We review the latest advance and summarize the fabrication methods, types and applications of hollow fibers. We mainly introduce the fabrication methods of hollow fibers, including co-extrusion/co-axial spinning methods, template methods, 3D printing methods, electrospinning methods, self-crimping methods and gas foaming process. Meanwhile, we summarize four types of hollow fibers: one-layered hollow fibers, multi-layered hollow fibers, multi-hollow fibers and branched hollow fibers. Next, we focus on the main applications of hollow fibers, such as gas separation, cell culture, microfluidic channels, artificial tubular tissues, etc. Finally, we present the prospects of the future trend of development. The review would promote the further development of hollow fibers and benefit their advance in sensing, bioreactors, electrochemical catalysis, energy conversion, microfluidics, gas separation, air purification, drug delivery, functional materials, cell culture and tissue engineering. This review has great significance for the design of new functional materials and development of devices and systems in the related fields.

Pyridine Grafted on SnO2 -Loaded Carbon Nanotubes Acting as Cocatalyst for Highly Efficient Electroreduction of CO2

Sn-based electrocatalysts have shown great potential in the future industrial application of CO₂ electroreduction (CO₂ ER) to C₁ products due to their non-toxicity and low price. However, it is a great challenge to fabricate a Sn-based electrocatalytic system with high performance and stability. Herein, grafted pyridine was innovatively coupled with SnO₂ to construct an organic-inorganic composite (SnO₂ /Py-CNTO) for highly efficient CO₂ ER. The detailed studies showed that pyridine and protonated pyridine coexist on the surface of SnO₂ /Py-CNTO, and both play distinctive roles in promoting the selectivity of CO₂ ER. Benefiting from the merits, SnO₂ /Py-CNTO delivered an excellent faradaic efficiency (FE) of 96 % for CO₂ ER at -1.29 V_RHE where the HCOOH production with 85 % FE dominated, and good stability for 32 h electrolysis. The theoretical calculations showed that protonated pyridine not only facilitates the CO₂ adsorption and HCOOH desorption, but also significantly reduces the limiting potential for the conversion of CO₂ to HCOOH.