Hyunjoo Lee

As a catalyst, single-atom platinum may provide an ideal structure for platinum minimization. Herein, a single-atom catalyst of platinum supported on titanium nitride nanoparticles were successfully prepared with the aid of chlorine ligands. Unlike platinum nanoparticles, the single-atom active sites predominantly produced hydrogen peroxide in the electrochemical oxygen reduction with the highest mass activity reported so far. The electrocatalytic oxidation of small organic molecules, such as fo

Activity revived: Platinum nanoparticles (cuboctahedra, cubes, and porous particles, see picture, from left to right) capped with alkylammonium ions are synthesized by manipulating the reduction kinetics. The catalytic activity of these nanoparticles is superior to that of nanoparticles whose shape was controlled with a polymeric capping agent and foreign metal ions.

Single-atom catalysts (SACs) provide an ideal platform for reducing noble-metal usage. SACs also exhibit unusual catalytic properties due to the absence of a metal surface. The role of the support may have a significant effect on the catalytic properties, similar to that of the ligand molecules in homogeneous catalysts. Here, the support effect was demonstrated by preparing a single-atom platinum catalyst on two different supports: titanium carbide (Pt1/TiC) and titanium nitride (Pt1/TiN). The f

Direct methane conversion into value-added products has become increasingly important. Because of inertness of methane, cleaving the first C–H bond has been very difficult, requiring high reaction temperature on the heterogeneous catalysts. Once the first C–H bond becomes activated, the remaining C–H bonds are successively dissociated on the metal surface, hindering the direct methane conversion into chemicals. Here, a single-atom Rh catalyst dispersed on ZrO 2 surface has been synthesized and u

Arsenite [As(III)] and arsenate [As(V)] are highly toxic aquatic contaminants. Since arsenite is more mobile in natural waters and less efficiently removed in adsorption/coagulation processes than arsenate, the oxidation of arsenite to arsenate is desirable in water treatment. We performed the photocatalytic oxidation of arsenite in aqueous TiO2 suspension and investigated the effects of pH, dissolved oxygen, humic acid (HA), and ferric ions on the kinetics and mechanisms of arsenite oxidation.

Abstract Electrochemical water splitting is promising for utilizing intermittent renewable energy. The sluggish kinetics of the oxygen evolution reaction (OER), however, is a bottleneck in obtaining high efficiency. Only a few OER electrocatalysts have been developed for the use in acidic media despite the importance of a proton exchange membrane (PEM) water electrolyzer. IrO 2 is the only material that is both active and stable for the OER in highly corrosive acidic conditions. Herein, a facile

Abstract Single‐atom catalysts (SACs), in which metal atoms are dispersed on the support without forming nanoparticles, have been used for various heterogeneous reactions and most recently for electrochemical reactions. In this Minireview, recent examples of single‐atom electrocatalysts used for the oxygen reduction reaction (ORR), hydrogen oxidation reaction (HOR), hydrogen evolution reaction (HER), formic acid oxidation reaction (FAOR), and methanol oxidation reaction (MOR) are introduced. Man

Minimizing the use of precious metal catalysts is important in many applications. Single-atom catalysts (SACs) have received much attention because all of the metal atoms can be used for surface reactions. However, SACs cannot catalyze some important reactions that require ensemble sites. Here, Rh catalysts were prepared by treating 2 wt % Rh/CeO₂ hydrothermally at 750 °C for 25 h. Nearly 100% dispersion was obtained, but the surface Rh atoms were not isolated (denoted as ENS). They c

Co3O4 is an attractive alternative to precious metal catalyst for CO oxidation due to its low cost and earth abundance, but its high catalytic activity is severely degraded in the presence of water. Here, we show that doping La into Co3O4 surfaces significantly enhances CO oxidation activity under moisture-rich condition. While bare Co3O4 is deactivated under moisture, the La-doped Co3O4 catalysts exhibit greatly improved activity and water resistance. The higher ratio of active Co3+ on the La-d

Abstract Single atomic Pt catalyst can offer efficient utilization of the expensive platinum and provide unique selectivity because it lacks ensemble sites. However, designing such a catalyst with high Pt loading and good durability is very challenging. Here, single atomic Pt catalyst supported on antimony‐doped tin oxide (Pt1/ATO) is synthesized by conventional incipient wetness impregnation, with up to 8 wt% Pt. The single atomic Pt structure is confirmed by high‐angle annular dark field scann

Ceria-supported Pd nanoparticles are known to be efficient catalysts for vehicle exhaust purification, especially diesel oxidation. The exhaust often undergoes harsh conditions, suffering from high temperature up to ∼750 °C. These conditions cause Pd nanoparticles to sinter, losing the catalytic active sites. In addition, carbonate and sulfate species might be formed on the catalyst surface, blocking the active sites with degraded activity. Hydrothermal treatment on Pd/CeO 2 affects the catalyst

Abstract Single‐atom catalysts (SACs) have emerged as promising materials in heterogeneous catalysis. Previous studies reported controversial results about the relative level in activity for SACs and nanoparticles (NPs). These works have focused on the effect of metal atom arrangement, without considering the oxidation state of the SACs. Here, we immobilized Pt single atoms on defective ceria and controlled the oxidation state of Pt SACs, from highly oxidized (Pt 0 : 16.6 at %) to highly metalli