Ki Tae Park

Electrochemical nitrate reduction (NO3RR) has emerged as a sustainable route for green ammonia (NH3) synthesis, simultaneously enabling the remediation of nitrate-contaminated wastewater and supporting carbon-neutral nitrogen cycling. However, achieving a delicate balance between suppressing the competitive hydrogen evolution reaction (HER) and ensuring sufficient protonation for NH3 formation remains a major challenge. Here, we present a bismuth-doped heterostructured oxide-derived copper (Bi/HOD-Cu) electrode that addresses this challenge through catalytic cooperation. The Cu2O/Cu heterostructure of HOD-Cu accelerates the initial electron transfer and promotes *NO3 to *NO2 conversion, while controlled Bi incorporation effectively suppresses HER and stabilizes the key *NO2 intermediate, confirmed by in situ Raman spectroscopy. This cooperative mechanism drives highly selective protonation toward NH3. Accordingly, the optimized Bi0.7/HOD-Cu electrode achieves an NH3 Faradaic efficiency (FE) of 94.3% with a partial current density of –278.3 mA·cm–2 at –1.4 V vs RHE. When integrated into a zero-gap membrane electrode assembly (MEA) electrolyzer, the electrode maintains an NH3 FE of 80.1% at a practical current density of 400 mA·cm–2 over 50 h of continuous operation, demonstrating its scalability toward sustainable ammonia production.

The application of a nickel foam-based macroporous structure with asymmetric binder engineering significantly enhances electrolyte transport and interfacial CO ₂ regeneration in liquid-fed electrochemical reactive carbon capture.

The electrochemical carbon dioxide reduction reaction (CO ₂ RR) represents a promising approach for the sustainable production of value‐added chemicals from CO ₂ . However, maintaining long‐term operational stability under industrially relevant high current densities remains a major challenge, primarily due to electrolyte flooding and the salt formation including carbonate and bicarbonate species, which severely compromise the performance of gas diffusion electrodes (GDEs). In this article, we present an advanced gas diffusion layer (GDL) design incorporating multiwalled carbon nanotubes (CNTs) into porous carbon‐based microporous layers. The resulting architecture facilitates the formation of a continuous, hydrophobic CNT–polytetrafluoroethylene (PTFE) network via preferential PTFE alignment along the CNT surfaces. This hydrophobic CNT–PTFE network effectively mitigates electrolyte flooding while maintaining efficient gas transport pathways. As a result, the CNT‐reinforced GDE demonstrated substantially enhanced CO ₂ RR performance, sustaining a CO Faradaic efficiency above 80% for 150 h at a current density of 400 mA cm ⁻² . In contrast, conventional carbon‐based GDEs exhibited rapid performance decay within 10 h under same conditions. These findings highlight that microstructural engineering of the GDL, via the formation of a hydrophobic CNT–PTFE network, provides a robust and scalable strategy for enhancing flooding resistance and operational durability in CO ₂ RR systems.

The electrochemical reduction of CO ₂ (CO ₂ RR) to liquid fuels and chemicals offers a sustainable route to close the carbon cycle. Solid‐state electrolyte (SSE) systems have recently emerged as a breakthrough platform, enabling the direct synthesis of high‐purity liquid products. Here, a novel Nafion‐based porous solid electrolyte (NPSE) with tunable thickness and porosity is presented, replacing conventional bead‐type ion‐exchange resins. The structural tunability of NPSEs plays a critical role in determining CO ₂ RR performance. Furthermore, a Nafion‐titanium dioxide (TiO ₂ ) composite NPSE (NPSE‐TiO ₂ ) is developed, in which TiO ₂ nanoparticles significantly enhance the selectivity and productivity of formic acid. The NPSE‐TiO ₂ achieves a record‐high Faradaic efficiency (FE _HCOOH ) of 98.6%, the highest value reported to date among SSE systems, along with a high partial current density ( j _HCOOH ) of 431.8 mA cm ⁻² , yielding electrolyte‐free formic acid with a single‐pass concentration of 17.4 wt.%. Mechanistic investigations reveal that TiO ₂ promotes the transport of formate anions (HCOO ⁻ ), suppressing back‐diffusion of formic acid to the cathode and stabilizing cathodic pH.