Jun Ho Shim

Bidirectional LDH–selenide conversion, dynamic reconstruction, and interfacial engineering regulate electronic structure and active-phase evolution, providing design principles for stable, efficient, and scalable water-splitting electrocatalysts.

Spinel metal oxides such as NiAl ₂ O ₄ are attractive electrocatalysts for alkaline water splitting but are often limited by low surface area, poor conductivity, and sluggish reaction kinetics. Herein, we report a bifunctional MOF–spinel heterostructured catalyst, Fe‐ZIF‐8@NiAl ₂ O ₄ , constructed by integrating solvothermally synthesized spinel NiAl ₂ O ₄ with iron‐doped ZIF‐8 without post‐synthetic pyrolysis. Benefiting from the porous, nitrogen‐rich MOF scaffold and the structurally robust spinel backbone, the composite delivers low overpotentials of 231 mV for the oxygen evolution reaction (OER) and 109 mV for the hydrogen evolution reaction (HER) at 10 mA cm ⁻² , together with Tafel slopes of 97.45 and 239.29 mV dec ⁻¹ , respectively. The enhanced activity originates from synergistic Fe–Ni interfacial interactions that facilitate electronic redistribution, accelerate charge transfer kinetics, and promote the in situ formation of catalytically active NiFe (oxy)hydroxide species during operation. Importantly, Fe‐ZIF‐8@NiAl ₂ O ₄ exhibits excellent durability and stable overall water splitting performance, retaining bulk crystallinity while undergoing beneficial surface reconstruction under prolonged electrolysis. This work establishes MOF hybridization as an effective strategy to activate Al‐based spinel oxides and provides practical design insights for developing cost‐effective, noble‐metal‐free electrocatalysts for sustainable hydrogen production.

Electrochemical nitrogen reduction reaction (NRR) provides a promising pathway for sustainable ammonia synthesis under ambient conditions and direct integration with renewable electricity. However, practical implementation remains limited by sluggish N ₂ activation, severe competition from the hydrogen evolution reaction (HER), low ammonia partial current densities, and insufficient long‐term stability. Existing studies frequently address these challenges separately, focusing on catalyst classes or mechanistic pathways, leaving a gap between atomic‐scale materials design and system‐level requirements for scalable operation. In this Review, we present an integrative perspective on electrocatalytic NRR that links reaction kinetics, descriptor‐guided materials design, and reactor‐level considerations. Emerging catalyst architectures, including single‐atom, dual‐atom, vacancy‐engineered, and metal‐free systems, are critically evaluated, highlighting how cooperative active sites, electronic‐structure modulation, and defect chemistry regulate N ₂ adsorption, stabilization of key intermediates (particularly NNH), and suppression of HER. Mechanistic descriptors, scaling relations, and design principles are discussed alongside experimental performance trends to clarify thermodynamic and kinetic limits governing selectivity. Beyond catalyst discovery, we examine electrolyte and interphase engineering, gas–liquid–solid transport, pressure and flow management, durability, and ammonia handling. By connecting catalyst design, mechanistic descriptors, reactor constraints, and techno‐economic targets, this Review outlines credible pathways toward scalable electrochemical ammonia production.

Mn incorporation into NiAl-LDH kinetically suppresses OER, enabling selective nucleophilic small-molecule oxidation at low potentials and reducing anodic energy requirements for efficient hydrogen generation.

The oxygen evolution reaction (OER) remains a critical kinetic bottleneck in water electrolysis for sustainable hydrogen production, necessitating the development of efficient and durable electrocatalysts. Herein, a sulfur‐incorporation strategy is employed to regulate the activity and stability of CoFeCr hydroxide toward OER in alkaline and seawater environments. Sulfur‐incorporated CoFeCr hydroxide (S‐CoFeCr‐OH) is synthesized via a two‐step hydrothermal–sulfurization process, which preserves the nanosheet architecture while enabling uniform sulfur incorporation into the hydroxide lattice without forming inactive sulfide phases. As a result, S‐CoFeCr‐OH delivers a low overpotential of 289 mV at 10 mA cm ⁻² with a reduced Tafel slope of 56.8 mV dec ⁻¹ , accompanied by accelerated charge–transfer kinetics, an enlarged electrochemical surface area, and enhanced intrinsic activity as evidenced by current densities normalized to the electrochemically active surface area. Notably, the catalyst exhibits excellent durability over 40 h and strong tolerance to chloride‐containing environments. This behavior is attributed to sulfur‐derived anionic surface modulation acting synergistically with chromium‐mediated electronic and structural stabilization, enabling sustained OER performance under alkaline seawater conditions. These findings highlight the effectiveness of a cooperative cation–anion codoping strategy that integrates sulfur‐mediated anionic modulation with multimetal hydroxide chemistry, providing a viable design principle for robust and earth‐abundant OER electrocatalysts for practical seawater electrolysis.

We report the rational design of a high-performance bifunctional electrocatalyst by incorporating tungsten into oxygen-deficient NiFe layered double hydroxide (NiFeW-LDH) nanosheets grown in situ on nickel foam via a one-pot hydrothermal method. The resulting NiFeW-LDH@NF electrode features a porous nanosheet network that enhances the surface area and interfacial electron transport. Tungsten integration tunes the electronic structure, increases oxygen vacancy concentration, and facilitates water molecule adsorption, thereby improving both oxygen evolution reaction and hydrogen evolution reaction (OER and HER) kinetics in 1.0 M KOH. The optimized catalyst achieves low overpotentials of 325 mV and 356 mV at 100 mA cm^-2 for OER and HER, respectively. In a two-electrode configuration, it enables efficient overall water splitting and seawater electrolysis with cell voltages of 1.646 and 1.693 V, respectively. Electrochemical analyses, including impedance spectroscopy, pH- and temperature-dependent kinetics, and turnover frequency measurements, confirm enhanced charge transfer, reduced activation energy, and accelerated reaction rates. Density functional theory calculations further reveal favorable d-band center shifts and intermediate adsorption energetics, supporting the experimental observations. These results demonstrate that NiFeW-LDH@NF is a cost-effective, robust, and scalable electrocatalyst for sustainable hydrogen production in both freshwater and seawater environments.

Engineered hydrophobic–hydrophilic regions tune catalyst wettability to control the triple-phase boundary, promoting N ₂ adsorption while limiting proton transport. This enhances NRR selectivity and suppresses competing HER.