In this work, we report a robust Ru phosphide (RuP) catalyst, which exhibits high propylene selectivity for propane dehydrogenation, whereas monometallic Ru nanoparticles (NPs) result in cracking. X-ray photoelectron spectroscopy, synchrotron X-ray absorption spectroscopy, transmission CO-IR of the reduced catalyst, and high-angle annular dark-field scanning transmission electron microscopy are used to identify the surface structure of NPs with different P/Ru atomic ratios, changing from Ru to Ru2P to RuP with increasing P loading. In addition to improving the olefin selectivity, increasing the P/Ru ratio leads to higher turnover rates and lowers the deactivation rate. P is thought to act as a structural promoter to reduce the Ru ensemble size, decreasing the hydrogenolysis rate. In addition, increasing the P/Ru ratio leads to a decrease in the energy of the Ru valence orbitals, which are suggested to weaken metal-adsorbate bond energies and reactant surface coverages.
The development of efficient catalytic electrode toward oxygen reduction reaction (ORR) is still a great challenge for the wide use of zinc–air batteries. Herein, Co2N nanoparticles (NPs) anchored on N‐doped carbon from cattail were verified with excellent catalytic performances for ORR. The onset and half‐wave potentials over the optimal catalyst reach to 0.96 V and 0.84 V, respectively. Current retention rates of 96.8% after 22‐h test and 98.8% after running 1600 s were obtained in 1 M methanol solution. Density functional theory simulation proposes an apparently increased electronic states of Co2N in N‐doped carbon layer close to the Fermi level. Higher charge density, favorable adsorption, and charge transfer of intermediates originate from the coexistence of Co2N NPs and N atoms in carbon skeleton. The superior catalytic activity of composites also was confirmed in zinc–air batteries. This novel catalytic property and controllable preparation approach of Co2N‐carbon composites provide a promising avenue to fabricate metal‐containing catalytically active carbon from biomass.
This article describes the synthesis and catalytic properties of supported, 2–3 nm platinum phosphide (PtP2) nanoparticles (NPs). Depending on the P loading, two PtP2 structures are formed, that is, a PtP2 surface on a (metallic) Pt core (Pt@PtP2) and single-phase PtP2 NPs. The structures were determined using extended X-ray absorption fine structure , in situ synchrotron X-ray diffraction, and scanning transmission electron microscopy. In PtP2 NPs, Pt2+ ions are geometrically isolated by P2 2– ions, at a Pt–Pt distance of 4.02 Å, which is much longer than 2.78 Å in (metallic) Pt NPs. The oxidation state of Pt in PtP2 NPs was determined by in situ X-ray absorption near-edge structure and in situ X-ray photoelectron spectroscopy and was found to be consistent with Pt2+ ions even after treatment in H2 at 550 °C. Unlike Pt NPs, which are highly active for propylene hydrogenation at room temperature, PtP2 NPs are not active below about 150 °C, suggesting the absence of metallic surface Pt. In contrast to metallic Pt, which is poorly selective for acetylene hydrogenation, PtP2 NPs display high selectivity toward ethylene. PtP2, also has high olefin selectivity for propane dehydrogenation, although the rate per g Pt is about 7 times lower than that of metallic Pt NPs of the same size. In situ resonant inelastic X-ray scattering spectroscopy shows that the energy of the filled Pt 5d valence orbitals is 1.5 eV lower than that of metallic Pt, which leads to weaker adsorbate binding consistent with its catalytic properties. A H2-stable Pt2+ site suggests different catalytic applications for these catalysts as compared to Pt NPs.
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