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Black phosphorus (BP), the bulk counterpart of monolayer phosphorene, is a relatively stable phosphorus allotrope at room temperature. However, monolayer phosphorene and ultra-thin BP layers degrade in ambient atmosphere. In this paper, we report the investigation of BP oxidation and discuss the reaction mechanism based on the x-ray photoelectron spectroscopy (XPS) data. The kinetics of BP oxidation was examined under various well-controlled conditions, namely in 5% O/Ar, 2.3% HO/Ar, and 5% O and 2.3% HO/Ar. At room temperature, the BP surface is demonstrated not to be oxidized at a high oxidation rate in 5% O/Ar nor in 2.3% HO/Ar, according to XPS, with the thickness of the oxidized phosphorus layer <5 Å for 5 h. On the other hand, in the O/HO mixture, a 30 Å thickness oxide layer was detected already after 2 h of the treatment. This result points to a synergetic effect of water and oxygen in the BP oxidation. The oxidation effect was also studied in applications to the electrical measurements of BP field-effect transistors (FETs) with or without passivation. The electrical performance of BP FETs with atomic layer deposition (ALD) dielectric passivation or h-BN passivation formed in a glove-box environment are also presented.

Supported multimetallic nanoparticles (NPs) are widely used in industrial catalytic processes, where the relation between surface structure and function is well-known. However, the effect of subsurface layers on such catalysts remains mostly unstudied. Here, we demonstrate a clear subsurface effect on supported 2 nm core-shell NPs with atomically precise and high temperature stable Pt3Mn intermetallic surface measured by in situ synchrotron X-ray Diffraction, difference X-ray Absorption Spectroscopy, and Energy Dispersive X-ray Spectroscopy. The NPs with a Pt3Mn subsurface have 98% selectivity to C-H over CC bond activation during propane dehydrogenation at 550 °C compared with 82% for core-shell NPs with a Pt subsurface. The difference is correlated with significant reduction in the heats of reactant adsorption due to the Pt3Mn intermetallic subsurface as discerned by theory as well as experiment. The findings of this work highlight the importance of subsurface for supported NP catalysts, which can be tuned via controlled intermetallic formation. Such approach is generally applicable to modifying multimetallic NPs, adding another dimension to the tunability of their catalytic performance. Disciplines

Supported nanoparticles are broadly employed in industrial catalytic processes, where the active sites can be tuned by metal-support interactions (MSIs). Although it is well accepted that supports can modify the chemistry of metal nanoparticles, systematic utilization of MSIs for achieving desired catalytic performance is still challenging. The developments of supports with appropriate chemical properties and identification of the resulting active sites are the main barriers. Here, we develop two-dimensional transition metal carbides (MXenes) supported platinum as efficient catalysts for light alkane dehydrogenations. Ordered Pt3Ti and surface Pt3Nb intermetallic compound nanoparticles are formed via reactive metal-support interactions on Pt/Ti3C2Tx and Pt/Nb2CTx catalysts, respectively. MXene supports modulate the nature of the active sites, making them highly selective toward C–H activation. Such exploitation of the MSIs makes MXenes promising platforms with versatile chemical reactivity and tunability for facile design of supported intermetallic nanoparticles over a wide range of compositions and structures.

An inverse Pd-Zr model catalyst was prepared by chemical vapor deposition (CVD) using zirconium-t-butoxide (ZTB) as an organometallic precursor. Pd-Zr interaction was then investigated with focus on the correlation of reforming performance with the oxidation state of Zr. As test reactions, dry reforming of methane (DRM) and methanol steam reforming (MSR) were chosen. Depending on treatments, either ZrOH or ZrO overlayers or Zr as sub-nanometer clusters could be obtained. Following the adsorption of ZTB on Pd(111), a partially hydroxylated Zr-containing layer was formed, which can be reduced to metallic Zr by thermal annealing in ultrahigh vacuum, leading to redox-active Zr sub-nanometer clusters. Complementary density functional theoretical (DFT) calculations showed that a single layer of ZrO on Pd(111) can be more easily reduced toward the metallic state than a double- and triple layer. Also, the initial and resulting layer compositions greatly depend on gas environment. The lower the water background partial pressure, the faster and more complete the reduction of Zr species to Zr on Pd takes place. Under methanol steam reforming conditions, water activation by hydroxylation of Zr occurs. In excess of methanol, strong coking is induced by the Pd/ZrOH interface. In contrast, dry reforming of methane is effectively promoted if these initially metallic Zr species are present in the pre-catalyst, leading to a Pd/ZrOH phase boundary by oxidative activation under reaction conditions. These reaction-induced active sites for DRM are stable with respect to carbon blocking or coking. In essence, Zr doping of Pd opens specific CO activation channels, which are absent on pure metallic Pd.

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The strength of metal-support bonding in heterogeneous catalysts determines their thermal stability, therefore, a tremendous amount of effort has been expended to understand metal-support interactions. Herein, we report the discovery of an anomalous "strong metal-support bonding" between gold nanoparticles and "nano-engineered" FeO substrates by in situ microscopy. During in situ vacuum annealing of Au-FeO dumbbell-like nanoparticles, synthesized by the epitaxial growth of nano-FeO on Au nanoparticles, the gold nanoparticles transform into the gold thin films and wet the surface of nano-FeO, as the surface reduction of nano-FeO proceeds. This phenomenon results from a unique coupling of the size-and shape-dependent high surface reducibility of nano-FeO and the extremely strong adhesion between Au and the reduced FeO. This strong metal-support bonding reveals the significance of controlling the metal oxide support size and morphology for optimizing metal-support bonding and ultimately for the development of improved catalysts and functional nanostructures.