Noble Metal Surfaces Research Articles

Enhancement of Photocatalytic Antimicrobial Performance via Generation and Diffusion of ROS

Review Enhancement of Photocatalytic Antimicrobial Performance via Generation and Diffusion of ROS Xiaojuan Bai 1,2,*, Yihan Cao 1, Bowen Zhu 1, Rujiao Liu 1, Jiaqian Dong 1, and Hua Yang 1 1 Key Laboratory of Urban Stormwater System and Water Environment, Ministry of Education, Beijing University of Civil Engineering and Architecture, Beijing 100044, China 2 Beijing Energy Conservation & Sustainable Urban and Rural Development Provincial and Ministry Co-construction Collaboration Innovation Center, Beijing University of Civil Engineering and Architecture, Beijing 100044, China * Correspondence: baixiaojuan@bucea.edu.cn Received: 8 June 2024; Revised: 8 August 2024; Accepted: 20 August 2024; Published: 20 September 2024 Abstract: The increasing prevalence of antibiotic-resistant infections globally emphasizes the urgent need for effective antimicrobial strategies. Photocatalysts, known for their efficiency, broad-spectrum activity, and environmental benefits, present a promising alternative. With the development of natural solar light driven photocatalysts, the antimicrobial and bactericidal range has been further extended. Photocatalytic materials can be activated by various light wavelengths to generate reactive oxygen species (ROS), which can effectively eliminate a wide range of pathogenic microorganisms including bacteria, fungi, and protozoa. However, the limited optical response range, suboptimal bandgap, and slow electron cycling limit the efficient generation of ROS, resulting in lower sterilization efficiency of photocatalytic antimicrobials. Additionally, the short half-life and limited migration distance of ROS restrict their antimicrobial activity. This review focuses on the process and mechanism of ROS generation in photocatalytic reactions, and highlighting the recent advances in the typical photocatalysts. We also explore strategies to enhance ROS diffusion and utilization, including morphology control, noble metal deposition, doping, co-catalyst loading, vacancy introduction, surface functionalization, and heterojunction construction. These strategies aim to increase the efficiency of ROS generation and prolong their activity, thereby enhancing the overall antimicrobial effectiveness. Thereafter, the review presents state-of-the-art applications of photocatalysts in water purification, medical coatings, and air disinfection. Furthermore, it explores key challenges and opportunities that may drive future innovations and advancements in photocatalytic antimicrobial applications, aiming to develop more effective and sustainable solutions.

(Invited) Probe the Reaction Intermediates on Noble Metal Electrodes during Oer with Vibrational Sum Frequency Spectroscopy

Electrochemical water splitting on noble metal surface is an important reaction of both fundamental and application interest. It is well known that the bottleneck of this reaction is the poor kinetics for oxygen generation from water oxidation. Despite of years study, the mechanisms in terms of the roles of the thin oxides film that formed on the metal surface before/during oxygen evolution are still inexplicit. One of the main reasons is the lack of molecular level information about the oxide thin film structures. In this study, we investigated the electrochemical oxidation of gold and platinum in solutions with different pHs by employing surface specific vibrational sum frequency spectroscopy (VSFS)1-3. By analyzing the potential dependent behaviors of different types of adsorbed species, we could gain molecular level information regarding the structures and formation mechanisms of metal-oxides. The results of this study will provide essential data toward understanding the oxygen evolution mechanism and also suggest strategies for developing better water splitting catalysts. [1]. Zhang, I. Y.; Zwaschka, G.; Wang, Z.; Wolf, M.; Campen, R. K.; Tong, Y., Resolving the chemical identity of H2SO4 derived anions on Pt(111) electrodes: they're sulfate. Physical Chemistry Chemical Physics 2019, 21 (35), 19147-19152.[2]. Zwaschka, G.; Wolf, M.; Campen, R. K.; Tong, Y., A Microscopic Model of the Electrochemical Vibrational Stark Effect: Understanding VSF Spectroscopy of (bi)Sulfate on Pt(111). Surf. Sci. 2018, 678, 78-85.[3]Gong, X.; Campen, R. K.; Tong, Y. Direct Observation of the Potential-Dependent Protonation and Reorientation of 4-(Dimethylamino)pyridine on Gold Electrodes. J. Phys. Chem. C 2023, 127 (33), 16615-16622. DOI: 10.1021/acs.jpcc.3c03038.

Direct Cation Stabilization Effects of CO Dimerization for Boosting C2 Pathways of CO2 Reduction on Noble Metal Surfaces

Direct Cation Stabilization Effects of CO Dimerization for Boosting C₂ Pathways of CO₂ Reduction on Noble Metal Surfaces

Facile Preparation of TiO2NTs/Au@MOF Nanocomposites for High-Sensitivity SERS Sensing of Gaseous VOC.

Surface-enhanced Raman spectroscopy (SERS) is a promising and highly sensitive molecular fingerprint detection technology. However, the development of SERS nanocomposites that are label-free, highly sensitive, selective, stable, and reusable for gaseous volatile organic compounds (VOCs) detection remains a challenge. Here, we report a novel TiO2NTs/AuNPs@ZIF-8 nanocomposite for the ultrasensitive SERS detection of VOCs. The three-dimensional TiO2 nanotube structure with a large specific surface area provides abundant sites for the loading of Au NPs, which possess excellent local surface plasmon resonance (LSPR) effects, further leading to the formation of a large number of SERS active hotspots. The externally wrapped porous MOF structure adsorbs more gaseous VOC molecules onto the noble metal surface. Under the synergistic mechanism of physical and chemical enhancement, a better SERS enhancement effect can be achieved. By optimizing experimental conditions, the SERS detection limit for acetophenone, a common exhaled VOC, is as low as 10-11 M. And the relative standard deviation of SERS signal intensity from different points on the same nanocomposite surface is 4.7%. The acetophenone gas achieves a 1 min response and the signal reaches stability in 4 min. Under UV irradiation, the surface-adsorbed acetophenone can be completely degraded within 40 min. The experimental results demonstrate that this nanocomposite has good detection sensitivity, repeatability, selectivity, response speed, and reusability, making it a promising sensor for gaseous VOCs.

Direct Cation Stabilization Effects of CO Dimerization for Boosting C2 Pathways of CO2 Reduction on Noble Metal Surfaces

The carbon dioxide reduction reaction (CO2RR) is one of the most promising solutions for realizing carbon neutralization via converting the emitted CO2 into value‐added chemicals. The CC coupling step for CO dimerization is the rate‐determining step for C2 pathways, which have not been thoroughly investigated. Herein, the direct cation stabilization effects on CO dimerization for *OCCO formation on the representative Cu(100) and Pt(100) surfaces are investigated. Density functional theory calculations show that the presence of alkali metal ions plays a vital role in promoting the coupling of *CO monomers on both metal surfaces, where Cu shows a stronger stabilization effect. More importantly, a strong linear correlation (R2 ≈ 0.9) between the dimer stabilization energy and the reaction energy is revealed for the first time, which is a promising indicator for the selectivity of C2 pathways. Further investigations on electronic structures reveal that the promoting effect on *OCCO formation is strongly related to the negative charges of the molecules, in which the negative charge accumulation is favored by the directional electron transfer due to the chemisorption of *OCCO on Cu(100) surface. This work offers insights into the understanding of CC coupling reactions for CO2RR mechanisms.

A simple, controllable, and scalable synthetic strategy for highly uniform N-doped carbon coating on nanoparticles

The carbon coating enables nanoparticles to withstand harsh environments, but achieving uniformity and scalability for their industrial use remains a challenge. In this work, we present a simple, controllable, and scalable strategy for one-pot coating with an N-doped carbon layer on the surface of various nanoparticles, including semiconductors, oxides, transition metals, and noble metals. Uniform coverage of the N-doped carbon layer was achieved through an autogenic pressure reaction of gaseous species derived from starting precursors in a closed reactor. The thickness of the coating layer could be precisely controlled by adjusting the amount of precursor, even down to the 1 nm level, because the precursor is completely consumed in the reactor without any loss. The crystallinity of the N-doped carbon layer could be modified by altering the coating temperature. Moreover, the results demonstrate that this coating process can be applied to different types of nanoparticles. Tests confirmed that nanoparticles retain their inherent nature while exhibiting more stable and enhanced properties after the N-doped carbon coating. We believe this approach offers a straightforward synthetic route for the design and application of nanoparticle coatings.

Morphological effect on Core@shell AuAg nanoparticles for detecting p‐aminothiophenol dimerization by surface‐enhanced Raman spectroscopy

AbstractA series of non‐spherical metallic Au and bimetallic core@shell AuAg nanoparticles (NPs) have been synthesized for SERS improvements. The bimetallic core@shell AuAg NPs were obtained through a controlled overgrowth of an Ag shell onto the surface of two types of non‐spherical Au NPs, used as seeds, Au nanooctaheda (Au NOc) and Au nanotriangles (Au NTs). This Ag overgrowth was able to produce bimetallic core@shell structures such as nanocubes and nanopyramids, respectively. Transmission electron microscopy (TEM) was used to determine the particle size and particle morphology for metallic and bimetallic NPs, and energy‐dispersive X‐ray (EDX) elemental mapping analysis confirmed the core@shell structure of the bimetallic NPs. The plasmonic absorption bands exhibited for each nanosystem were observed by UV–vis spectroscopy. The concentration of Au and Ag in the bimetallic systems was determined by inductively coupled plasma mass spectrometry (ICP‐MS). After synthesis and characterization, p‐aminothiophenol (PATP) was used as a model analyte to investigate the surface‐enhanced Raman spectroscopy (SERS) capabilities of the synthesized metallic and bimetallic nanosystems. In PATP, a dimerization reaction to 4,4′‐dimercaptoazobenzene (DMAB) is produced when it is adsorbed onto the surface of certain noble metals. This SERS analysis was performed at 10−4 M of PATP and by using two different laser wavelengths (532 and 785 nm) in all cases. In this context, we were able to detect the dimerization reaction of PATP to DMAB only for the bimetallic structures and under the 532 nm laser line. Moreover, we have found that the dimerization capacity also depends on the nanoparticle morphology.

Noble metal clusters substitution in porous Ni substrate renders high mass-specific activities toward oxygen evolution reaction and methanol oxidation reaction

The sluggish reaction kinetics of the oxygen evolution reaction (OER) and methanol oxidation reaction (MOR) remain obstacles to the commercial promotion of water splitting and direct methanol fuel cells. Considering the vital role of noble metals in electrocatalytic activity, this work focuses on the rational synthesis of Ni-noble metal composite nanocatalysts for overcoming the drawbacks of high cost and susceptible oxidized surfaces of noble metals. The inherent catalytic activity is improved by the altered electronic structure and effective active sites of the catalyst induced by the size effect of noble metal clusters. In particular, a series of Ni-noble metal nanocomposites are successfully synthesized by partially introducing noble metal into Ni with porous interfacial defects derived from Ni-Al layered double hydroxide (LDH). The Ni10Pd1 nanocomposite exhibits high OER catalytic activity with an overpotential of 0.279 V at 10 mA/cm2, surpassing Ni10Ag1 and Ni10Au1 counterparts. Furthermore, the average diameter of Pd clusters gradually increases from 5.57 nm to 44.44 nm with the increased proportion of doped Pd, leading to the passivation of catalytic activity due to the exacerbated surface oxidation of Pd in the form of Pd2+. After optimization, Ni10Pd1 delivers significantly enhanced OER and MOR electroactivities and long-term stability compared to that of Ni2Pd1, Ni1Pd1 and Ni1Pd2, which is conducive to the effective utilization of Pd and alleviation of surface oxidation.

Fabrication of CuO/Au Nanowires on a Copper Substrate for Ultra-Sensitive SERS Sensors

To optimize the surface-enhanced Raman (SERS) phenomenon on the surface of noble metals, gold nanoparticles were synthesized on the surface of nano-sized copper wires to enhance the dispersion of gold particles on the research surface. A simple experimental procedure was carried out in two stages. First, the thin copper substrate was lightly oxidized with ammonium persulfate in an alkaline environment, then incubated at 200oC for 3 hours to form copper nanowires that exist stably on the substrate surface. Immediately afterward, highly uniform CuO/Au nanowires were formed by the chemical reduction of HAuCl4 on the surface of the oxidized copper plate. The results show that gold nanoparticles of about 5 nm were attached to CuO nanowires with a length of up to 10 µm and a diameter between 100 and 300 nm. The X-ray energy dispersive spectrum demonstrated a uniform distribution of gold particles. The CuO/Au structure was used as a SERS substrate to detect methylene blue at a low concentration of 10 pM corresponding to 2 signals at the peaks 1395 cm−1 and 1625 cm−1 as the C-H and C-C deformation vibrations of the aromatic ring. The logarithms of the methylene blue concentrations were linearly proportional to their SERS signal intensity of methylene blue at the peak of 1625 cm-1 with a value R2 = 0.96. The signals of SERS for methylene blue at twelve different points on the material sample showed no significant differences in both intensity and shape of the spectrum, with an RSD value of 5.9%.

Unraveling Enyne Bonding via Dehydrogenation–Hydrogenation Processes in On‐Surface Synthesis with Terminal Alkynes

AbstractOn‐surface reactions of terminal alkynes in ultrahigh vacuum have attracted widespread attention due to their high technological promise. However, employing different precursors and substrate materials often intricate reaction schemes appear far from being well‐understood. Thus, recent investigations of alkyne coupling on noble metal surfaces suggest non‐dehydrogenative scenarios, contradicting earlier reports. Herein, the study employs noncontact atomic force microscopy (nc‐AFM) with high spatial resolution to conclusively characterize exemplary alkyne coupling products. Contrary to initial interpretations proposing dehydrogenative homocoupling on Ag(111), bond‐resolved AFM imaging reveals the expression of enyne motifs. Based on complementary, extensive density functional theory calculations, the pertaining reaction mechanisms are explored. It is proposed that enyne formation initiates with a direct carbon–carbon coupling between two alkyne groups, followed by surface‐assisted dehydrogenation‐hydrogenation processes. Thereby consecutive steps of atomic hydrogen cleavage, surface migration and recombination to a different carbon atom enable bridging via carbon–carbon double bonding. The new results shed light on subtle, but crucial surface‐mediated hydrogen transfer processes involved in the chemical bond formation, which are suggested to be of general relevance in on‐surface synthesis.

Highly area-selective atomic layer deposition of device-quality Hf1-xZrxO2 thin films through catalytic local activation

Area-selective atomic layer deposition (AS-ALD) has garnered significant attention as a promising bottom-up patterning process for sub-10 nm scale technology, offering unmatched atomic-scale precision and pattern alignment capabilities in 3D nanofabrication. In this study, we present a groundbreaking methodology for achieving highly selective deposition of Hf1-xZrxO2 (HZO) thin films through catalytic local activation on noble metal surfaces (Ru and Pt) and TiN surfaces, without the need for surface inhibitory materials. To achieve inherent selectivity on metal surfaces, we employ O2 gas as a mildly oxidizing reactant and utilize cyclopentadienyl-tris(dimethylamido)-hafnium(zirconium) [Hf(Zr)Cp(NMe2)3] precursors, which require strong oxidizing agents, for HZO film formation. By catalytically dissociating O2 molecules, we successfully achieved area-selective deposition of HZO films greater than ∼7 nm on both blanket Ru versus Si substrates and Pt/Si-patterned substrates. Furthermore, we demonstrate the selective deposition of antiferroelectric HZO thin films with high dielectric constants of 34 and 31 on Ru and TiN substrates, respectively, using the inherent AS-ALD method combined with post-ozone treatment. Importantly, this catalytic local activation approach for achieving inherent deposition selectivity expands the potential utility of 3D bottom-up nanopatterning processes in next-generation nanoelectronic applications.

Molybdenum(0)-Tricarbonyl Complex Supported by an Azacalix-pyridine Ligand: Synthesis, Characterization, Surface Deposition and Conversion to a Molybdenum(VI)-Trioxo Complex with O2.

Adsorption of metal-organic complexes on metallic surfaces to produce well-defined single site catalysts is a novel approach combining the advantages of homogeneous and heterogeneous catalysis. To avoid the "surface trans-effect" a dome-shaped molybdenum(0) tricarbonyl complex supported by an tolylazacalix[3](2,6)pyridine ligand is synthesized. This vacuum-evaporable complex both activates CO and reacts with molecular oxygen (O2) to form a Mo(VI) trioxo complex which in turn is capable of catalytically mediating oxygen transfer. The molybdenum tricarbonyl- and trioxo complexes are investigated in the solid state, in homogeneous solution and on noble metal surfaces (Cu, Au) employing a range of spectroscopic and analytical methods.

Selectivity Control by Relay Catalysis in CO and CO2 Hydrogenation to Multicarbon Compounds.

ConspectusThe hydrogenative conversion of both CO and CO2 into high-value multicarbon (C2+) compounds, such as olefins, aromatic hydrocarbons, ethanol, and liquid fuels, has attracted much recent attention. The hydrogenation of CO is related to the chemical utilization of various carbon resources including shale gas, biomass, coal, and carbon-containing wastes via syngas (a mixture of H2 and CO), while the hydrogenation of CO2 by green H2 to chemicals and liquid fuels would contribute to recycling CO2 for carbon neutrality. The state-of-the-art technologies for the hydrogenation of CO/CO2 to C2+ compounds primarily rely on a direct route via Fischer-Tropsch (FT) synthesis and an indirect route via two methanol-mediated processes, i.e., methanol synthesis from CO/CO2 and methanol to C2+ compounds. The direct route would be more energy- and cost-efficient owing to the reduced operation units, but the product selectivity of the direct route via FT synthesis is limited by the Anderson-Schulz-Flory (ASF) distribution. Selectivity control for the direct hydrogenation of CO/CO2 to a high-value C2+ compound is one of the most challenging goals in the field of C1 chemistry, i.e., chemistry for the transformation of one-carbon (C1) molecules.We have developed a relay-catalysis strategy to solve the selectivity challenge arising from the complicated reaction network in the hydrogenation of CO/CO2 to C2+ compounds involving multiple intermediates and reaction channels, which inevitably lead to side reactions and byproducts over a conventional heterogeneous catalyst. The core of relay catalysis is to design a single tandem-reaction channel, which can direct the reaction to the target product controllably, by choosing appropriate intermediates (or intermediate products) and reaction steps connecting these intermediates, and arranging optimized yet matched catalysts to implement these steps like a relay. This Account showcases representative relay-catalysis systems developed by our group in the past decade for the synthesis of liquid fuels, lower (C2-C4) olefins, aromatics, and C2+ oxygenates from CO/CO2 with selectivity breaking the limitation of conventional catalysts. These relay systems are typically composed of a metal or metal oxide for CO/CO2/H2 activation and a zeolite for C-C coupling or reconstruction, as well as a third or even a fourth catalyst component with other functions if necessary. The mechanisms for the activation of H2 and CO/CO2 on metal oxides, which are distinct from that on the conventional transition or noble metal surfaces, are discussed with emphasis on the role of oxygen vacancies. Zeolites catalyze the conversion of intermediates (including hydrocracking/isomerization of heavier hydrocarbons, methanol-to-hydrocarbon reactions, and carbonylation of methanol/dimethyl ether) in the relay system, and the selectivity is mainly controlled by the Brønsted acidity and the shape-selectivity or the confinement effect of zeolites. We demonstrate that the thermodynamic/kinetic matching of the relay steps, the proximity and spatial arrangement of the catalyst components, and the transportation of intermediates/products in sequence are the key issues guiding the selection of each catalyst component and the construction of an efficient relay-catalysis system. Our methodology would also be useful for the transformation of other C1 molecules via controlled C-C coupling, inspiring more efforts toward precision catalysis.

Discarding metal incorporation in pyrazole macrocycles and the role of the substrate on single-layer assemblies.

Pyrazole derivatives are key in crystal engineering and liquid crystal fields and thrive in agriculture, pharmaceutical, or biomedicine industries. Such versatility relies in their supramolecular bond adaptability when forming hydrogen bonds or metal-pyrazole complexes. Interestingly, the precise structure of pyrazole-based macrocycles forming widespread porous structures is still unsolved. We bring insight into such fundamental question by studying the self-assembled structures of a bis-pyrazole derivative sublimed in ultra-high-vacuum conditions (without solvents) onto the three (111) noble metal surfaces. By means of high-resolution scanning tunneling microscopy that is validated by gas phase density functional theory calculations, we find a common hexagonal nanoporous network condensed by triple hydrogen bonds at the molecule-metal interface. Such assembly is disrupted and divergent after annealing: (i) on copper, the molecular integrity is compromised leading to structural chaos, (ii) on silver, an incommensurate new oblique structure requiring molecular deprotonation is found and, (iii) on gold, metal-organic complexes are promoted yielding irregular chain structures. Our findings confirm the critical role of these metals on the different pyrazole nanoporous structure formation, discarding their preference for metal incorporation into the connecting nodes whenever there is no solvent involved.

Photodeposition synthesis of hollow g-C3N4/Ag nanotubes with high oxidation properties to enhance visible-light photocatalytic performance

A hollow Ag-deposited g-C3N4 nanotube (CNNT/Ag) with high oxidation properties was synthesized using a simple photodeposition method. The g-C3N4 nanotubes provided abundant active sites and a large specific surface area for effective deposition of Ag nanoparticles. The Ag NPs expanded the light absorption range of g-C3N4 through surface plasmon resonance (SPR) effects and acted as an electron acceptor, effectively inhibiting the recombination of photogenerated carriers, thereby improving the charge separation efficiency. The CNNT/Ag composites exhibited excellent photocatalytic performance in the visible light degradation of rhodamine B and tetracycline, 6.42 and 2.16 times higher than pure g-C3N4, respectively. The increased photocatalytic activity of CNNT/Ag composites was attributed to the synergistic electron transfer interface between CNNT and Ag NPs, promoting the migration efficiency of photo-generated carriers. This work presented a promising strategy for constructing effective photocatalysts for degrading organic pollutants using morphology optimization and SPR effects on noble metal surfaces.

Cancer Marker Immunosensing through Surface-Enhanced Photoluminescence on Nanostructured Silver Substrates.

Nanostructured noble metal surfaces enhance the photoluminescence emitted by fluorescent molecules, permitting the development of highly sensitive fluorescence immunoassays. To this end, surfaces with silicon nanowires decorated with silver nanoparticles in the form of dendrites or aggregates were evaluated as substrates for the immunochemical detection of two ovarian cancer indicators, carbohydrate antigen 125 (CA125) and human epididymis protein 4 (HE4). The substrates were prepared by metal-enhanced chemical etching of silicon wafers to create, in one step, silicon nanowires and silver nanoparticles on top of them. For both analytes, non-competitive immunoassays were developed using pairs of highly specific monoclonal antibodies, one for analyte capture on the substrate and the other for detection. In order to facilitate the identification of the immunocomplexes through a reaction with streptavidin labeled with Rhodamine Red-X, the detection antibodies were biotinylated. An in-house-developed optical set-up was used for photoluminescence signal measurements after assay completion. The detection limits achieved were 2.5 U/mL and 3.12 pM for CA125 and HE4, respectively, with linear dynamic ranges extending up to 500 U/mL for CA125 and up to 500 pM for HE4, covering the concentration ranges of both healthy and ovarian cancer patients. Thus, the proposed method could be implemented for the early diagnosis and/or prognosis and monitoring of ovarian cancer.

Observing π-Au Interaction between Aromatic Molecules and Single Au Nanodimers with a Subnanometer Gap by SERS.

Interface interaction between aromatic molecules and noble metals plays a prominent role in fundamental science and technological applications. However, probing π-metal interactions under ambient conditions remains challenging, as it requires characterization techniques to have high sensitivity and molecular specificity without any restrictions on the sample. Herein, the interactions between polycyclic aromatic hydrocarbon (PAH) molecules and Au nanodimers with a subnanometer gap are investigated by surface-enhanced Raman spectroscopy (SERS). A cleaner and stronger plasmonic field of subnanometer gap Au nanodimer structures was constructed through solvent extraction. High sensitivity and strong π-Au interaction between PAHs and Au nanodimers are observed. Additionally, the density functional theory calculation confirmed the interactions of PAHs physically absorbed on the Au surface; the binding energy and differential charge further theoretically indicated the correlation between the sensitivity and the number of PAH rings, which is consistent with SERS experimental results. This work provides a new method to understand the interactions between aromatic molecules and noble metal surfaces in an ambient environment, also paving the way for designing the interfaces in the fields of catalysis, sensors, and molecular electronics.

Nanotube-Like Electronic States in [5,5]-C90 Fullertube Molecules.

Fullertubes, that is, fullerenes consisting of a carbon nanotube moiety capped by hemifullerene ends, are emerging carbon nanomaterials whose properties show both fullerene and carbon nanotube (CNT) traits. Albeit it may be expected that their electronic states show a certain resemblance to those of the extended nanotube, such a correlation has not yet been found or described. Here it shows a scanning tunneling microscopy (STM) and spectroscopy (STS) characterization of the adsorption, self-assembly, and electronic structure of 2D arrays of [5,5]-C90 fullertube molecules on two different noble metal surfaces, Ag(111) and Au(111). The results demonstrate that the shape of the molecular orbitals of the adsorbed fullertubes corresponds closely to those expected for isolated species on the grounds of density functional theory calculations. Moreover, a comparison between the electronic density profiles in the bands of the extended [5,5]-CNT and in the molecules reveals that some of the frontier orbitals of the fullertube molecules can be described as the result of the quantum confinement imposed by the hemifullerene caps to the delocalized band states in the extended CNT. The results thus provide a conceptual framework for the rational design of custom fullertube molecules and can potentially become a cornerstone in the understanding of these new carbon nanoforms.

Chemical functionalization of commercial Pt/C electrocatalyst towards formic acid electrooxidation

The chemical functionalization on the noble metal surface will undoubtedly affect the electrode reaction process. In this work, 1,10-phenanthroline (PL) functionalized commercial Pt/C electrocatalyst (Pt/C@PL) is successfully achieved through a convenient post-modification strategy. The adsorption of PL molecules on Pt/C electrocatalyst surface effectively isolates the continuous Pt atoms. Consequently, the formic acid electrooxidation reaction (FAOR) on Pt/C@PL electrocatalyst only obeys the dehydrogenation pathway, in which the generation of COads is completely suppressed. Compared with unfunctionalized commercial Pt/C electrocatalyst, Pt/C@PL electrocatalyst reveals a 11.4/16.8-fold increase in mass/specific activity, exhibiting a prominently enhanced electrocatalytic performance towards FAOR. This strategy, the chemical functionalization on the electrocatalysts surface, is easy to operate and applicable to commercial electrocatalyst that already exist, which also provides a simple and efficient way in the design of advanced electrocatalysts towards many other electrochemical reactions.

Development of a Simple Electroless Method for Depositing Metallic Pt-Pd Nanoparticles over Wire Gauge Support for Removal of Hydrogen in a Nuclear Reactor.

Electroless noble metal deposition on the conducting substrate is widely used to obtain the desired film or coating on the substrate of interest. Wire-gauge-based Pt/Pd/Pt-Pd (individually, sequentially, and simultaneously deposited) catalysts have been developed using formaldehyde and sodium formate as reducing agents. Various surface pretreatment methods like SnCl2 + PdCl2 seeding, oxalic acid etching, and HCl activation (etching) have been employed to obtain the desired noble metal coating. Minimum time duration was observed for simultaneously deposited catalysts using formaldehyde as a reducing agent. Prepared catalysts were characterized for noble metal deposition, coating kinetics, surface morphology, and binding energy. The catalyst was found to be active for H2 and O2 recombination reactions for hydrogen mitigation applications in nuclear reactors.