Band structure and dispersion engineering of strongly coupled plasmon-phonon-polaritons in graphene-integrated structures

Publisher's PDFWe theoretically investigate the polaritonic band structure and dispersion properties of graphene using transfer matrix methods, with strongly coupled graphene plasmons (GPs) and molecular infrared vibrations as a representative example. Two common geometrical con- figurations are considered: graphene coupled subwavelength dielectric grating (GSWDG) and graphene nanoribbons (GNR). By exploiting the dispersion and the band structure, we show the possibility of tailoring desired polaritonic behavior in each of the two configurations. We compare the strength of coupling occurring in both structures and find that the interaction is stronger in GNR than that of GSWDG structure as a result of the stronger field confinement of the edge modes. The band structure and dispersion analysis not only sheds light on the physics of the hybridized polariton formation but also offers insight into tailoring the optical response of graphene light-matter interactions for numerous applications, such as biomolecular sensing and detection.University of Delaware. Bartol Research Institute

FeNi Cubic Cage@N-Doped Carbon Coupled with N‑Doped Graphene toward Efficient Electrochemical Water Oxidation

Oxygen evolution reaction (OER) is of great significance in electrochemical water splitting on industrial scale, which suffers from the slow kinetics and large overpotential, thus setting the main obstacle for efficient water electrolysis. To pursue cost-effective OER electrocatalysts with high activity and durable stability, we here set a facile strategy to prepare N-doped graphene supported core–shell FeNi alloy@N-doped carbon nanocages (FeNi@NC-NG) by annealing graphene oxides supported Prussian blue analogues under H₂/Ar atmosphere. Based on the specific structural benefits, the present catalyst shows superior OER catalytic activity than precious metal catalyst of RuO₂ and Ir/C, with a low overpotential of 270 mV for 10 mA cm^–2, as well as high stability. The simple synthesis process and outstanding electrocatalytic performances show great potential of FeNi@NC-NG to replace the noble metal-based catalysts toward electrochemical water oxidation

Prussian Blue Analogue-Derived Iron Sulfide–Cobalt Sulfide Nanoparticle-Decorated Hollow Nitrogen-Doped Carbon Nanocubes for the Selective Electrochemical Detection of Dopamine

Hollow nanostructures have gained much attention in the electroanalytical field. This work describes the synthesis of CoS2–FeS2 nanoparticle-decorated hollow nitrogen-doped carbon nanocubes (CoS2–FeS2/HNCC) by a direct sulfidation of the Co–Fe Prussian blue analogue at a high temperature. By integrating dual-phase metal sulfides and a nitrogen-doped carbon matrix, this hollow nanocubic structure provides rich catalytic centers, enhanced conductivity, large surface area, and 3D-porous channels, which all contribute to the adsorption and catalysis of dopamine. The CoS2–FeS2/HNCC-modified glassy carbon electrode demonstrates excellent electrocatalytic activity for dopamine. Under the optimal parameters, the electrochemical sensor exhibits a wide detection range (0.05–90 μM), a low limit of detection (9.3 nM, S/N = 3), and a high sensitivity (91.6 μA μM–1 cm–2) along with excellent selectivity, reproducibility, reusability, and stability. This method has also been applied for the detection of dopamine in human urine samples and displays satisfactory results

Precise Interstitial Built-In Electric Field Tuning for Hydrogen Evolution Electrocatalysis

The built-in electric field (BEF) has become an effective means of adjusting the electronic structure and hydrogen spillover to influence the adsorption of intermediates. However, the previously reported BEF cannot be tuned continuously and precisely. Herein, a series of nanocatalysts with interstitial BEF were successfully synthesized, and the effect of precisely tuned interstitial BEF on the intermediate’s adsorption and hydrogen spillover was systematically investigated using changing the insertion of interstitial B. Three catalysts with different BEF strengths were obtained by changing the interstitial content (B0.22-Cu/NC, B0.30-Cu/NC, B0.41-Cu/NC), and it was demonstrated that B0.30-Cu/NC gave the best catalytic performance for hydrogen evolution reactions (HERs). The turnover frequency (TOF) value is shown to reach 0.36 s–1 at just −0.1 V vs. RHE, which is about 3 times that of Cu (0.12 s–1). For the HER, it is one of the best Cu-based catalysts reported to date (Table S3). Besides, when the catalyst was applied to the cathode of the PEM water electrolyzer, B0.30-Cu/NC exhibited long-time stability at a water-splitting current density of 500 mA cm–2. Density functional theory and in situ Raman spectroscopy suggest that a suitable interstitial BEF can not only optimize the intermediate’s adsorption but also promote hydrogen spillover

Monometallic Ultrasmall Nanocatalysts via Different Valence Atomic Interfaces Boost Hydrogen Evolution Catalysis

Synergistic monometallic nanocatalysts have attracted much attention due to their high intrinsic activity properties. However, current synergistic monometallic nanocatalysts tend to suffer from long reaction paths due to restricted nanoscale interfaces. In this paper, we synthesized the interstitial compound N-Pt/CNT with monometallic atomic interfaces. The catalysts are enriched with atomic interfaces between higher valence Ptδ+ and Pt0, allowing the reaction to proceed synergistically within the same component with an ideal reaction pathway. Through ratio optimization, N2.42-Pt/CNT with a suitable ratio of Ptδ+ and Pt0 is synthesized. And the calculated turnover frequency of N2.42-Pt/CNT is about 37.4 s–1 (−0.1 V vs reversible hydrogen electrode (RHE)), six times higher than that of the commercial Pt/C (6.58 s–1), which is the most intrinsically active of the Pt-based catalysts. Moreover, prepared N2.42-Pt/CNT exhibits excellent stability during the chronoamperometry tests of 200 h. With insights from comprehensive experiments and theoretical calculations, Pt with different valence states in monometallic atomic interfaces synergistically accelerates the H2O dissociation step and optimizes the Gibbs free energy of H* adsorption. And the existence of desirable hydrogen transfer paths substantially facilitates hydrogen evolution reaction kinetics