Despite its multidisciplinary interests and technological importance, the shape control of Ru nanocrystals still remains a great challenge. In this article, we demonstrated a facile hydrothermal approach toward the controlled synthesis of Ru nanocrystals with the assistance of first-principles calculations. For the first time, Ru triangular and irregular nanoplates as well as capped columns with tunable sizes were prepared with high shape selectivity. In consistency with the experimental observations and density functional theory (DFT) calculations confirmed that both the intrinsic characteristics of Ru crystals and the adsorption of certain reaction species were responsible for the shape control of Ru nanocrystals. Ultrathin Ru nanoplates exposed a large portion of (0001) facets due to the lower surface energy of Ru(0001). The selective adsorption of oxalate species on Ru(10-10) would retard the growth of the side planes of the Ru nanocrystals, while the gradual thermolysis of the oxalate species would eliminate their adsorption effects, leading to the shape evolution of Ru nanocrystals from prisms to capped columns. The surface-enhanced Raman spectra (SERS) signals of these Ru nanocrystals with 4-mercaptopyridine as molecular probes showed an enhancement sequence of capped columns > triangle nanoplates > nanospheres, probably due to the sharp corners and edges in the capped columns and nanoplates as well as the shrunk interparticle distance in their assemblies. CO-selective methanation tests on these Ru nanocrystals indicated that the nanoplates and nanospheres had comparable activities, but the former has much better CO selectivity than the latter.

The fundamental understanding of the structural effects of supported metal catalysts at molecular level is extremely important for developing high-performance catalysts that are widely used in industry, which is still a long-standing attractive but challenging topic in multidisciplinary fields. In this work, we report the strong effects of local coordination structures on the catalytic activity of subnanometric PtO x clusters over CeO 2 nanowires in low-temperature CO oxidation as a probe reaction. Atoms and subnanometric clusters of Pt were deposited to form the coordination structure of PtO x on the well-defined CeO 2 nanowires with mainly exposing (110) facets. The reactivity of active sites and the variation of the local coordination structures of the PtO x sites were deeply investigated with in-situ spectroscopic experiments assisted by density functional theory simulations. According to our observation, although the highly dispersed Pt sites at subnanometric scale could provide increased accessible sites, some of the Pt sites could not show high activity for CO oxidation due to the increased surrounding oxygen that seemed to overstabilize the Pt atoms. An increased proportion of both adsorbed CO intermediates on oxidized Pt sites and the interfacial lattice oxygen of PtO x clusters tended to become inactive on the samples with high coordination number of oxygen bonded to Pt sites (CN(Pt−O)), leading to the loss of effective active sites and the decrease in the catalytic activity. A relative small CN(Pt−O) in the subnanometric PtO x /CeO 2 NWs, which was found to be the appropriate structures for their catalytic performances, could remarkably increase the activity by about half an order of magnitude. We believe our investigation on the interfacial coordination structures effects of the subnanometric PtO x clusters dispersed on CeO 2 nanowires can provide some new basic chemical insights into the metal-support interfacial interactions of Pt/CeO 2 catalysts for understanding their catalytic performance in some relevant reactions.

Active center engineering at atomic level is a grand challenge for catalyst design and optimization in many industrial catalytic processes. Exploring new strategies to delicately tailor the structures of active centers and bonding modes of surface reactive intermediates for nanocatalysts is crucial to high-efficiency nanocatalysis that bridges heterogeneous and homogeneous catalysis. Here we demonstrate a robust approach to tune the CO oxidation activity over CeO2 nanowires (NWs) through the modulation of the local structure and surface state around Ln(Ce)' defect centers by doping other lanthanides (Ln), based on the continuous variation of the ionic radius of lanthanide dopants caused by the lanthanide contraction. Homogeneously doped (110)-oriented CeO2:Ln NWs with no residual capping agents were synthesized by controlling the redox chemistry of Ce(III)/Ce(IV) in a mild hydrothermal process. The CO oxidation reactivity over CeO2:Ln NWs was dependent on the Ln dopants, and the reactivity reached the maximum in turnover rates over Nd-doped samples. On the basis of the results obtained from combined experimentations and density functional theory simulations, the decisive factors of the modulation effect along the lanthanide dopant series were deduced as surface oxygen release capability and the bonding configuration of the surface adsorbed species (i.e., carbonates and bicarbonates) formed during catalytic process, which resulted in the existence of an optimal doping effect from the lanthanide with moderate ionic radius.