Tuning metal–support interaction has been considered as an effective approach to modulate the electronic structure and catalytic activity of supported metal catalysts. At the atomic level, the understanding of the structure–activity relationship still remains obscure in heterogeneous catalysis, such as the conversion of water (alkaline) or hydronium ions (acid) to hydrogen (hydrogen evolution reaction, HER). Here, we reveal that the fine control over the oxidation states of single-atom Pt catalysts through electronic metal–support interaction significantly modulates the catalytic activities in either acidic or alkaline HER. Combined with detailed spectroscopic and electrochemical characterizations, the structure–activity relationship is established by correlating the acidic/alkaline HER activity with the average oxidation state of single-atom Pt and the Pt–H/Pt–OH interaction. This study sheds light on the atomic-level mechanistic understanding of acidic and alkaline HER, and further provides guidelines for the rational design of high-performance single-atom catalysts.

Single-atom catalysts have recently been applied in many applications such as CO oxidation. Experimental in situ investigations into this reaction, however, are limited. Hereby, we present a suite of operando/in situ spectroscopic experiments for structurally well-defined atomically dispersed Rh on phosphotungstic acid during CO oxidation. The identification of several key intermediates and the steady-state catalyst structure indicate that the reactions follow an unconventional Mars-van Krevelen mechanism and that the activation of O2 is rate-limiting. In situ XPS confirms the contribution of the heteropoly acid support while in situ DRIFT spectroscopy consolidates the oxidation state and CO adsorption of Rh. As such, direct observation of three key components, i.e., metal center, support and substrate, is achieved, providing a clearer picture on CO oxidation on atomically dispersed Rh sites. The obtained information are used to engineer structurally similar catalysts that exhibit T20 values up to 130 °C below the previously reported Rh1/NPTA.

Blue phosphorus, a newly proposed allotrope of phosphorus, represents a promising 2D material with predicted large tunable band gap and high charge-carrier mobility. Here, we report a simple method for the growth of quasi-free-standing single layer blue phosphorus on tellurium functionalized Au(111) by using black phosphorus as the precursor. In situ low-temperature scanning tunneling microscopy (LT-STM) measurements were used to monitor the growth of the single-layer blue phosphorus, which forms triangular structures arranged hexagonally on the tellurium layer. As revealed by in situ X-ray photoelectron spectroscopy, LT-STM measurements, and density functional theory calculation, the blue phosphorus layer weakly interacts with the underlying tellurium layer.

Graphene oxide (GO) is promising for a variety of applications due to its excellent dispersibility and processability. However, current chemical oxidation routes have several drawbacks, including the use of explosive oxidizing agents, residual metal ions contaminations, and the creation of irreparable hole defects on the GO sheet. The electrochemical exfoliation and oxidation of graphite is a potentially greener approach without the need for extensive purification steps. Most reported electrochemical methods employ a single preformed bulk graphite as electrode, which limits their scalability, reproducibility, and degree of oxidation. Herein, we reported a novel mechanically assisted electrochemical method to produce graphene oxide directly from graphite flakes. The electrochemically derived graphene oxide (EGO) shows a good degree of oxidation but with less physical defects than chemically derived graphene oxide (CGO). EGO has good dispersibility in water and various solvents and, in particular, displays better long-term stability in ethanol when compared with CGO. Notably, unlike conventional CGO, EGO can undergo facile thermal conversion at 200 °C in air to conductive thermally processed EGO, which is highly desirable for heat/chemical-sensitive applications.

Hybrid organic-inorganic perovskites have recently emerged as potential disruptive photovoltaic technology. However, the toxicity of lead used in state-of-the-art hybrid perovskites solar cell prevents large-scale commercialization, which calls for lead-free alternatives. Sn-based perovskites have been considered as alternatives but they are limited by rapid oxidation and decomposition in ambient air. Here, an Sn-based two-dimensional hybrid organic-inorganic perovskites [A 2 B (n-1) Sn n I (3n+1) ] (n = 1 and 2) are reported with improved air stability, using bulky stilbene derivatives as the organic cations (2-(4-(3-fluoro)stilbenyl)ethanammonium iodide (FSAI)). The moisture stability of the [(FSA) 2 SnI 4 ] perovskites is attributed to the hydrophobic properties of fluorine-functionalized organic chains (FSA), as well as the strong cohesive bonding in the organic chains provided by H bonds, CH···X type H bonds, weak interlayer F···F interaction, and weak face-to-face type π-π interactions. The photodetector device fabricated on exfoliated single crystal flake of [(FSA) 2 SnI 4 ] exhibits fast and stable photoconductor response.