Recently, the creation of new heterogeneous catalysts using the unique electronic/geometric structures of small metal nanoclusters (NCs) has received considerable attention. However, to achieve this, it is extremely important to establish methods to remove the ligands from ligand‐protected metal NCs while preventing the aggregation of metal NCs. In this study, the ligand‐desorption process during calcination was followed for metal‐oxide‐supported 2‐phenylethanethiolate‐protected gold (Au) 25‐atom metal NCs using five experimental techniques. The results clearly demonstrate that the ligand‐desorption process consists of ligand dissociation on the surface of the metal NCs, adsorption of the generated compounds on the support and desorption of the compounds from the support, and the temperatures at which these processes occurred were elucidated. Based on the obtained knowledge, we established a method to form a metal‐oxide layer on the surface of Au NCs while preventing their aggregation, thereby succeeding in creating a water‐splitting photocatalyst with high activity and stability.

Organic ligands on gold nanoclusters play important roles in regulating the structures of gold cores. However, the impact of the number and positions of the protecting ligands on gold-core structures remains unclear. We isolated thiolate-protected Au 25 cluster anions, [Au 25 (SC 2 Ph) 17 (Por) 1 ] − and [Au 25 (SC 2 Ph) 16 (Por) 2 ] − (SC 2 Ph = 2-phenylethanethiolate), obtained by ligand exchange of [Au 25 (SC 2 Ph) 18 ] − with one or two porphyrinthiolate (Por) ligands as mixtures of regioisomers. The ratio of two regioisomers in [Au 25 (SC 2 Ph) 17 (Por) 1 ] − as measured by 1 H NMR spectroscopy revealed that the selectivity could be controlled by the steric hindrance of the incoming thiols. Extended X-ray absorption fine structure studies of a series of porphyrin-coordinated gold nanoclusters clarified that the Au 13 icosahedral core in the Au 25 cluster was distorted through steric repulsion between porphyrin thiolates and phenylethanethiolates. This paper reveals interesting insights into the importance of the steric structures of protecting ligands for control over core structures in gold nanoclusters.

Although supported anionic gold nanoparticle catalysts have been theoretically investigated for their efficacy in activating O 2 in aerobic oxidation reactions, limited studies have been reported due to the difficulty of designing these catalysts. Herein, we developed a feasible method for preparing supported anionic gold nanoparticle catalysts using multivacant lacunary polyoxometalates with high negative charges. We confirmed the strong and robust electronic interaction between gold nanoparticles and multivacant lacunary polyoxometalates, and the electronic states of the supported gold nanoparticle catalysts can be sequentially modulated. Particularly, the catalyst prepared using [SiW 9 O 34 ] 10À acted as an efficient reusable heterogeneous catalyst, showing superior catalytic performance for the oxidative dehydrogenation of piperidone derivatives to the corresponding enaminones and remarkably higher stability than supported gold nanoparticle catalysts without this modification.

We introduce a catalyst composed of isolated Pt atoms surrounded by Ni atoms in a Ni−Pt alloy (iso-Pt), which was prepared on aluminum oxide (Al 2 O 3 ) obtained by a simple impregnation method with typical hydrogen reduction pretreatment. This catalyst exhibited a relatively high CH 4 -formation rate while maintaining excellent selectivity for CH 4 evolution, when compared to bulk Ni atoms (bulk-Ni), although bulk Pt atoms (bulk-Pt) produced CO rather than CH 4 . Kinetic studies revealed that one of the two roles of the iso-Pt species in the Ni−Pt alloy is to provide H 2 dissociation sites at low temperature, resulting in high CO 2 methanation activity. Fourier transform infrared spectroscopy clarified the second role of the iso-Pt species; tuning of the d-electronic state by alloying to surrounding Ni atoms leads to CO molecules that are strongly anchored to the iso-Pt atoms, which weakens the C−O bond of the CO species attached to the Pt atoms and improves the abilities of the surrounding Ni atoms to promote further methanation with hydrogen.

We elucidated the cooperative active sites of Ni–Pt alloy nanoparticles composed of Pt atoms isolated by Ni atoms and their neighboring Ni atoms for the efficient and selective hydrogenation of CO2 toward CH4. The stepwise methanation dynamics were revealed by in situ observations and transient changes in the infrared spectra during the hydrogenation of CO2. It was found that the hydrogenation of CO species attached to the isolated Pt atoms proceeded through a bridging CO species between isolated Pt atoms and their neighboring Ni atoms, leading to an excellent selectivity toward CH4. Kinetic studies revealed that the high H2 dissociation ability of the Pt species accelerated the hydrogenation of the carbon species over the surface of the Ni–Pt alloy, thereby avoiding the rate limitations of CH4 formation which are common for Ni catalysts. The bifunctional role of the isolated Pt atoms therefore allowed the efficient formation of CH4 while maintaining the excellent selectivity of the Ni catalyst toward CH4, despite Pt catalysts tending to favor CO production.

Rhodium-doped gallium oxide (Ga 2 O 3 :Rh) that was prepared by a simple coprecipitation method exhibited activity for the photocatalytic conversion of CO 2 by H 2 O under photoirradiation with light of >300 nm wavelength. Although Ga 2 O 3 is a wide-band-gap photocatalyst that is active only under photoirradiation with <300 nm light, the absorption edge shifted to >300 nm as a result of Rh doping. Ag−Cr-loaded Ga 2 O 3 :Rh (0.7 mol %) showed activity for the production of CO (3.9 μmol h −1 ) as a reduction product of CO 2 . The formation of a stoichiometric amount of O 2 indicated that H 2 O acts as an electron donor for the photocatalytic conversion of CO 2 . Characterization using several techniques such as X-ray absorption spectroscopy (XAS) revealed that after doping in Ga 2 O 3 the trivalent Rh species substituted not for the tetrahedral Ga site but for the octahedral Ga site of β-Ga 2 O 3 . From the result of DFT calculations, the new energy level owing to Rh 3+ was within the Ga 2 O 3 band gap. It was concluded that the new absorption due to the Rh d t 2g orbital to the conduction band contributed to the activity of photocatalytic conversion of CO 2 by H 2 O under photoirradiation with light of >300 nm wavelength.

The improvement of oxygen reduction reaction (ORR) catalysts is essential before polymer electrolyte fuel cells can be used widely. To this end, we established a simple method for the size-selective...

In this study, we explored the feasibility of using base metal catalysts for three-way catalysis. The catalysts contain up to three base metals that were chosen to replace or reduce use of platinum group metals (Rh, Pd, and Pt). The aim was to develop catalysts with high activities at low temperatures having robustness against oxygen concentration fluctuations. Various base metal catalysts supported on alumina [10 wt % X/Al2O3 (X = Fe, Co, Ni, or Cu), 10 wt % CuY/Al2O3 (Y = Mn, Fe, Co, or Ni; Cu/Y = 1:1 in atomic ratio), and 10 wt % CuNi–5 wt % Z/Al2O3 (Z = Mn, Fe, or Co; Cu/Ni = 1:1 in atomic ratio)] were tested by temperature-programmed reaction in NO–CO–C3H6–O2 flow and under fluctuating oxygen concentration conditions. We found that the rate of reduction of NO over the 10 wt % CuNi–5 wt % Fe/Al2O3 catalyst in the low-temperature region was comparable to that of 1 wt % Pt/Al2O3, and this catalyst was also tolerant to oxidative conditions to some extent. Ex situ characterization of the catalysts before and after the three-way catalytic reaction was carried out via powder X-ray diffraction, X-ray absorption spectroscopy, scanning transmission electron microscopy with an energy-dispersive X-ray spectrometer, and in situ diffuse reflectance infrared Fourier transform measurements and revealed that the presence of Fe species resulted in the significantly improved oxidation of C3H6 and, thus, an increased rate of reduction of NO.