Sang‐Il Choi 교수

Because H₂ is considered a promising clean energy source, water electrolysis has attracted great interest in related research and technology. Noble-metal-based catalysts are used as electrode materials in water electrolyzers, but their high cost and low abundance have impeded them from being used in practical areas. Recently, metal sulfides and phosphides based on earth-abundant transition metals have emerged as promising candidates for efficient water-splitting catalysts. Most studie

Nanoscale Pt-Ni bimetallic octahedra with controlled sizes have been actively explored in recent years owning to their outstanding activity for the oxygen reduction reaction (ORR). Here we report the synthesis of uniform 9 nm Pt-Ni octahedra with the use of oleylamine and oleic acid as surfactants and W(CO)6 as a source of CO that can promote the formation of {111} facets in the presence of Ni. Through the introduction of benzyl ether as a solvent, the coverage of both surfactants on the surface

The oxygen reduction reaction (ORR) on the cathode of a polymer electrolyte fuel cell requires the use of a catalyst based on Pt, one of the most expensive metals on the earth. A number of strategies, including optimization of shape or facet, formation of alloys with other metals, and incorporation of a different metal into the core, have been investigated to enhance the activity of a Pt-based catalyst and thus reduce the loading of Pt. This article reports the synthesis and characterization of

Abstract Long‐term catalyst stability is essential for the commercialization of hydrogen generation by electrocatalytic water‐splitting. Current research, however, mainly focuses on improving electrode activity of the hydrogen evolution reaction (HER) at the cathode and oxygen evolution reaction (OER) at the anode of electrolyzers, although the maintenance of long‐term performance poses a bigger challenge. To shift the focus of research to the issue of catalyst stability, this review describes t

The design and synthesis of Pt-based electrocatalysts for the hydrogen evolution reaction (HER) are of great importance for the successful development of hydrogen-based alternative energy technologies. Although Pt is considered to be the most active catalyst for the HER, its reaction performance is limited in alkaline solutions owing to a slow rate for water dissociation. Therefore, many research groups have intensively investigated reaction mechanisms and developed system designs and efficient

Pt-based nanoframe catalysts have been explored extensively due to their superior activity toward the oxygen reduction reaction (ORR). Herein, we report the synthesis of Pt-Ni multiframes, which exhibit the unique structure of tightly fused multiple nanoframes and reinforced by an embedded dendrite. Rapid reduction and deposition of Ni atoms on Pt-Ni nanodendrites induce the alloying/dealloying of Pt and Ni in the overall nanostructures. After chemical etching of Ni, the newly formed dendrite-em

Abstract Palladium has been recognized as the best anodic, monometallic electrocatalyst for the formic acid oxidation (FAO) reaction in a direct formic acid fuel cell. Here we report a systematic study of FAO on a variety of Pd nanocrystals, including cubes, right bipyramids, octahedra, tetrahedra, decahedra, and icosahedra. These nanocrystals were synthesized with approximately the same size, but different types of facets and twin defects on their surfaces. Our measurements indicate that the Pd

Abstract Water electrolysis is an important energy conversion technology used to produce hydrogen on a mass scale. Until now, special emphasis has been placed on technology development for water electrolysis in acidic electrolytes, owing to the more facilitated hydrogen production under acidic conditions compared to alkaline water electrolysis. Among various catalyst design concepts, bifunctional catalysts capable of driving low overpotentials for the hydrogen evolution reaction (HER) and oxygen

Modification of the electronic structure and lattice contraction of Pt alloy nanocatalysts through control over their morphology and composition has been a crucial issue for improving their electrocatalytic oxygen reduction reaction (ORR) activity. In the present work, we synthesized PtCo alloy nanocubes with controlled compositions (Pt(x)Co NCs, x = 2, 3, 5, 7, and 9) by regulating the ratio of surfactants and the amount of Co precursor to elucidate the effect of the composition of nanocatalyst

Colloidal, monodisperse, highly crystalline ITO nanoparticles with various particle sizes and tin contents were prepared by a one-pot thermal decomposition of tin and indium precursors in oleylamine. The PL emission maxima become blue-shifted as the particle size decreases and the tin content increases.

Abstract The harsh operating conditions of the oxygen evolution reaction (OER) in water electrolysis severely degrade the activity and stability of the electrocatalysts due to elemental leaching or particle agglomeration. Therefore, it is crucial to incorporate support materials that effectively immobilize catalyst particles for developing efficient OER catalysts. This review aims to highlight the role of MXene as a support material to improve the performance of OER catalysts. First, the extende

This review outlines the strategies and challenges of the state-of-the-art non-precious group metal-based catalysts toward water electrolysis.

A layered β-NiOOH crystal with undercoordinated facets is an active and economically viable nonnoble catalyst for the oxygen evolution reaction (OER) in alkaline electrolytes. However, it is extremely difficult to enclose the β-NiOOH crystal with undercoordinated facets because of its inevitable crystal transformation to γ-NiOOH, resulting in the exfoliation of the catalytic surfaces. Herein, we demonstrate {111}-faceted Ni octahedra as the parent substrates whose surfaces are easily transformed

The electrochemical reduction of CO₂ to form value-added chemicals receives considerable attention in recent years. Copper (Cu) is recognized as the only element capable of electro-reducing CO₂ into hydrocarbons with two or more carbon atoms (C₂₊), but the low product selectivity of the Cu-based catalyst remains a major technological challenge to overcome. Therefore, identification of the structural features of Cu-based catalysts is of great importance for the hi