The heterostructure of transition metal nanocrystal on two-dimensional (2D) materials exhibits unique physical and chemical properties through various interfacial interactions. It has been established that the atomic structure and strain in the vicinity of the interface determine the band structure and phonon modes of the nanocrystal, regulating the optical and electrical properties of such heterostructures. Hence, metal–support interfacial engineering is a demonstrated approach to acquiring desired properties of the nanocrystals. However, a fundamental understanding of the interfacial structures remains elusive and precise control of the interactions has yet achieved. Herein, we explore the regulation of interface on MoS₂ supported Pt nanocrystals which were prepared by reducing ultrasonic dispersed potassium chloroplatinate. The Pt-MoS₂ heterostructure interface was systematically studied by aberration corrected transmission electron microscopy. Three types of Pt-MoS₂ interfaces with distinct atomic configurations were identified. The strain within the Pt nanocrystals is sensitive to the atomic configuration of the supporting MoS₂, which regulates the size of the Pt nanocrystals. These results provide insights on tuning of nanocrystal strain, paving the way for precise control of 2D semiconductor heterostructures.

Formic acid oxidation (FAO) is a typical anode reaction in fuel cells that can be facilitated by modulating its direct and indirect reaction pathways. Herein, PtAu bimetallic nanoparticles loaded onto Co and N co-doping carbon nanoframes (CoNC NFs) were designed to improve the selectivity of the direct reaction pathway for efficient FAO. Based on these subtle nanomaterials, the influences of elemental composition and carbon-support materials on the two pathways of FAO were investigated in detail. The results of fuel cell tests verified that the appropriate amount of Au in PtAu/CoNC can promote a direct reaction pathway for FAO, which is crucial for enhancing the oxidation efficiency of formic acid. In particular, the obtained PtAu/CoNC with an optimal Pt/Au atomic ratio of 1:1 (PtAu/CoNC-3) manifests the best catalytic performance among the analogous obtained Pt-based electrocatalysts. The FAO mass activity of the PtAu/CoNC-3 sample reached 0.88 A·mg_Pt⁻¹, which is 26.0 times higher than that of Pt/C. The results of first-principles calculation and CO stripping jointly demonstrate that the CO adsorption of PtAu/CoNC is considerably lower than that of Pt/CoNC and PtAu/C, which indicates that the synergistic effect of Pt, Au, and CoNC NFs is critical for the resistance of Pt to CO poisoning. This work is of great significance for a deeper understanding of the oxidation mechanism of formic acid and provides a feasible and promising strategy for enhancing the catalytic performance of the catalyst by improving the direct reaction pathway for FAO.

Two-dimensional (2D) MoS₂ with appealing physical properties is a promising candidate for next-generation electronic and optoelectronic devices, where the ultrathin MoS₂ is usually laid on or gated by a dielectric oxide layer. The oxide/MoS₂ interfaces widely existing in these devices have significant impacts on the carrier transport of the MoS₂ channel by diverse interface interactions. Artificial design of the oxide/MoS₂ interfaces would provide an effective way to break through the performance limit of the 2D devices but has yet been well explored. Here, we report a high-performance MoS₂-based phototransistor with an enhanced photoresponse by interfacing few-layer MoS₂ with an ultrathin TiO₂ layer. The TiO₂ is deposited on MoS₂ through the oxidation of an e-beam-evaporated ultrathin Ti layer. Upon a visible-light illumination, the fabricated TiO₂/MoS₂ phototransistor exhibits a responsivity of up to 2,199 A/W at a gate voltage of 60 V and a detectivity of up to 1.67 × 10¹³ Jones at a zero-gate voltage under a power density of 23.2 μW/mm². These values are 4.0 and 4.2 times those of the pure MoS₂ phototransistor. The significantly enhanced photoresponse of TiO₂/MoS₂ device can be attributed to both interface charge transfer and photogating effects. Our results not only provide valuable insights into the interactions at TiO₂/MoS₂ interface, but also may inspire new approach to develop other novel optoelectronic devices based on 2D layered materials.

Surface engineering is known as an effective strategy to enhance the catalytic properties of Pt-based nanomaterials. Herein, we report on surface engineering Ni-Pt nanoalloys with a facile method by varying the Ni doping concentration and oleylamine/oleic- acid surfactant-mix. The alloy-composition, exposed facet condition, and surface lattice strain are, thereby manipulated to optimize the catalytic efficiency of such nanoalloys for methanol oxidation reaction (MOR). Exemplary nanoalloys including Ni_0.69Pt_0.31 truncated octahedrons, Ni_0.45Pt_0.55 nanomultipods and Ni_0.20Pt_0.80 nanoflowers are thoroughly characterized, with a commercial Pt/C catalyst as a common benchmark. Their variations in MOR catalytic efficiency are significant: 2.2 A/mg_Pt for Ni_0.20Pt_0.80 nanoflowers, 1.2 A/mg_Pt for Ni_0.45Pt_0.55 nanomultipods, 0.7 A/mg_Pt for Ni_0.69Pt_0.31 truncated octahedrons, and 0.6 A/mg_Pt for the commercial Pt/C catalysts. Assisted by density functional theory calculations, we correlate these observed catalysis-variations particularly to the intriguing presence of surface interplanar-strains, such as {111} facets with an interplanar-tensile-strain of 2.6% and {200} facets with an interplanar-tensile-strain of 3.5%, on the Ni_0.20Pt_0.80 nanoflowers.

The morphology and structural stability of metal/2D semiconductor interfaces strongly affect the performance of 2D electronic devices and synergistic catalysis. However, the structural evolution at the interfaces has not been well explored particularly at atomic resolution. In this work, we study the structural evolution of Au nanoparticles (NPs) on few-layer MoS₂ by high resolution transmission electron microscopy (HRTEM) and quantitative high-angle annular dark field scanning TEM. It is found that in the transition of Au from nanoparticles to dendrites, a dynamically epitaxial alignment between Au and MoS₂ lattices is formed, and Moiré patterns can be directly observed in HRTEM images due to the mismatch between Au and MoS₂ lattices. This epitaxial alignment can occur in ambient conditions, and can also be accelerated by the irradiation of high-energy electron beam. In situ observation clearly reveals the rotation of Au NPs, the atom migration inside Au NPs, and the transfer of Au atoms between neighboring Au NPs, finally leading to the formation of epitaxially aligned Au dendrites on MoS₂. The structural evolution of metal/2D semiconductor interfaces at atomic scale can provide valuable information for the design and fabrication of the metal/2D semiconductor nano-devices with desired physical and chemical performances.

A simple yet general one-step solvothermal method is applied to synthesize sub-7 nm monodispersed single-crystal NiPt₂ nanoparticles (NPs) with the morphology of truncated octahedrons in the alloying state of disordered atomic arrangements. The effective magnetic moments of these NPs exhibit an anomalous temperature dependency, increasing from approximately 0.9 μ_B/atom at 15 K to 1.9 μ_B/atom at 300 K. This is an increase by a factor of more than three compared with bulk Ni. On the basis of experiments involving X-ray absorption near-edge spectroscopy of the L3 edge for Pt and density functional theory calculations, the observed novel magnetism enhancement and its anomalous temperature dependence are attributed to the electron transfer arising from the thermal-activation effects.

We have demonstrated the improved performance of oxygen evolution reactions (OER) using Au/nickel phosphide (Ni₁₂P₅) core/shell nanoparticles (NPs) under basic conditions. NPs with a Ni₁₂P₅ shell and a Au core, both of which have well-defined crystal structures, have been prepared using solution-based synthetic routes. Compared with pure Ni₁₂P₅ NPs and Au-Ni₁₂P₅ oligomer-like NPs, the core/shell crystalline structure with Au shows an improved OER activity. It affords a current density of 10 mA/cm² at a small overpotential of 0.34 V, in 1 M KOH aqueous solution at room temperature. This enhanced OER activity may relate to the strong structural and effective electronic coupling between the single-crystal core and the shell.

Hollow and porous Pt-based nanomaterials are promising catalysts with applications in many sustainable energy technologies such as fuel cells. Economical and green synthetic routes are highly desirable. Here, we report a facile approach to prepare double- and single-layered Pt-Ni nanobowls (DLNBs and SLNBs) with porous shells. Microstructural analysis revealed that the shells were constructed of alloyed Pt-Ni nanocrystals and small amounts of Ni compounds. X-ray photoelectron spectra showed that their Pt 4f binding energies shifted in the negative direction compared to those of the commercial Pt/C catalyst. Furthermore, the DLNBs contained greater contents of oxidized Ni species than the SLNBs. The layer-controlled growth processes were confirmed by microscopy, and a formation mechanism was proposed based on the assistance of citrate and poly(vinylpyrrolidone) (PVP). For the methanol oxidation reaction, the DLNBs and SLNBs exhibited 2.9 and 2.5 times higher mass activities than that of the commercial Pt/C catalyst, respectively. The activity enhancements were attributed to electronic effects and a bifunctional mechanism. Chronoamperometry and prolonged cyclic voltammetry indicated that the Pt-Ni bowl-like structures had better electrochemical properties and structural stability than the commercial Pt/C catalyst, thus making the Pt-Ni nanobowls excellent electrocatalysts for use in direct methanol fuel cells.