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In this study we investigate how electronic properties of buried semiconductor/ionic liquid interfaces may influence on charging effects observed by X-ray photoelectron spectroscopy (XPS). Droplets of the ionic liquid 1-ethyl-3-methylimidazolium bis (trifluoromethylsulfonyl)imide ([EMIM][Tf2N]) were deposited on silicon and germanium semiconductor surfaces with different doping states. Core level spectra were recorded from the ionic liquid/ultra-high vacuum interface with and without irradiation of the droplets using low energy electrons from a flood gun. Changing electron intensity results in shifts of the binding energy of all XPS signals to lower values. Magnitude of shifts is found to directly depend on the intensity of the electron beam and to correlate with the nominal resistivity of the substrates. The observations are qualitatively explained by flood gun induced changes of the electronic properties of the [EMIM][Tf2N]/substrate interface and suggested to refer to space charge layer effects.

The ionic liquid [EMIM][TFSI] was investigated by X-ray Photoelectron Spectroscopy (XPS) on different substrates, ranging from metallic to semiconductor type materials. Parallel angle-resolved XPS was performed utilising a wide-angle lens hemispherical analyser with an acceptance angle of 60°. ARXPS data show no preferential orientation/accumulation of certain species at the ionic liquid/ultra-high vacuum interface. Charging caused by the electron emission process and electron flood gun experiments was recorded. The data indicate that the binding energies of the spectra depend on the properties of the substrate material, specifically on the substrate/ionic liquid interface. Observations are discussed by means of electric double layer and other processes that may effect on the potential of the ionic liquid.

New dye functionalized polymeric carbon nitrides with increased visible light response were designed and fabricated. In this research, Rose Bengal (RB) was immobilized on g-C3N4 (CN) and carboxylated g-C3N4 (CCN) through the formation of a covalent bond. The covalent bonding of Rose Bengal to the CN or CCN resulted in the transfer of electrons from the dye to the semiconductor and the enhancement of the light harvesting performance, which promoted the photocatalytic efficiency. The photocatalytic activity of CN, CCN, and their hybrids with RB toward selective oxidation of benzyl alcohol was investigated under the visible light irradiation. The results obtained from the GC–MS analyses related to the oxidation reaction displayed the highest percentage of benzyl alcohol conversion and benzaldehyde selectivity for the hybrid structures compared to the bare RB, CN, CCN, or a mixture of RB and CN (or CCN). The effect of several parameters, including the amount of photocatalyst and promoter, irradiation time, and photocatalyst type, was studied and optimized. The recovery of RB-CCN (the most active catalyst) was surveyed in five runs, and the results verify that the activity is mostly maintained. Finally, the optimized structure, energy gap, and frontier orbitals of Rose Bengal/graphitic carbon nitride were investigated by DFT methods.

This work focuses on the wettability transition of nodular cast iron (NCI) modified using a femtosecond laser-produced micro/nano-structure. Laser parameters such as laser fluences (0.10 to 3.18 J/cm2), and scan speed (0.2 to 1.0 mm/s) were varied to realize hierarchical or dual-phase structures. Raman spectroscopy was performed on samples treated at 0.10 to 0.63 J/cm2 to investigate the mechanism involved in the disappearance of the graphite nodule with increasing laser fluence. Just-after the laser treatment, surface was superhydrophilic in nature and progressively became superhydrophobic after cleaning and subsequent application of vacuum pressure for 8 h. In the present investigation, a static contact angle (SCA) of 164 ± 4° was measured. The temperature-dependent durability of the superhydrophobic surface was analyzed by heating at a temperature range from 80 °C to 240 °C. The results showed a stable superhydrophobic characteristic up to 120 °C even after five cycles of repetition. Scanning electron microscope (SEM) analysis was conducted to capture the micrograph of structures. Moreover, the chemisorption mechanism during the vacuum process and over the period was analyzed using X-ray photoelectron spectroscopy (XPS) that indicated a higher concentration of non-polar functional groups on the surface could effectively increase the SCA.

We investigated the effect of different electrolyte additives such as vinyl carbonate (VC), succinic anhydride (SA), and lithium bis(oxalato)borate (LiBOB) on the chemical composition of Solid Electrolyte Interphase (SEI) layer and the electrochemical performance of Si/MC electrodes. The electrochemical behavior of the Si/MC electrodes was evaluated by galvanostatic charge/discharge and rate capability tests. It was found that various electrolyte compositions result in the formation and the resulting properties of the SEI of the electrodes with different compounds. From X-ray Photoelectron Spectroscopy (XPS) analysis, the electrodes cycled in SA- and LiBOB-containing electrolytes show a higher amount of lithium carbonates and a thicker SEI layer than those in standard and VC-containing electrolyte. The electrode with VC 5w% shows an excellent reversible capacity of ∼1100 mAh g −1 up to 100 charge-discharge cycles.

The aging behavior of electrochemical double layer capacitors (EDLCs) based on activated carbon electrodes bound with poly(tetrafluoroethylene) (PTFE) was tested in electrolyte solutions based on acetonitrile (AN) and propylene carbonate (PC) at a constant elevated cell voltage of 3.5 V. The aging was quantified in terms of capacitance loss and resistance increase for the full cell and the individual electrodes. It is shown that the enhanced aging rate of symmetric EDLCs in either solvent at elevated voltages is dominated by the aging of a single electrode, and that the polarity of this limiting electrode depends directly on the solvent. In AN, the positive electrode ages much more rapidly than the negative, while in PC the negative electrode exhibits faster aging than the positive. After aging, the electrodes were investigated by nitrogen adsorption and X-ray photoelectron spectroscopy, revealing significant modifications of the electrode surface and providing clear evidence for the deposition of electrolyte degradation products on the electrodes.

The electrochemical doping of single-walled carbon nanotubes (SWCNTs) in 1 M Et4NBF4 in acetonitrile was investigated by in situ Raman spectroscopy. The capacitance was determined to be 82 F/g for the positive and 71 F/g for the negative SWCNT electrode, respectively, which approaches the typical values for microporous activated carbons used in supercapacitors. The changes in the Raman intensities and shifts of the D and G+ bands as well as of the radial breathing modes (RBMs) during electron and hole injection were studied as a function of the electrode potential. For the D and G+ bands, hole doping leads to strong upshifts which can be attributed to a stiffening of C–C bonds and the corresponding phonon modes. Electron doping results in much less pronounced changes in the band positions. The intensity attenuation of the RBM bands was found to be markedly different for semi-conducting and metallic SWCNTs, whereby sufficiently high doping leads to a loss of Raman intensity due to bleaching of electronic transitions. The main RBM bands upshift upon both electron and hole doping, which is attributed to changes in the chemical environment of individual SWCNTs upon charging and discharging of the electrochemical double layer within SWCNT bundles.

Highly oriented pyrolytic graphite (HOPG) in a solution of (C2H5)4NBF4 in propylene carbonate (PC) was investigated as a model system for the electrochemical double-layer capacitor (EDLC) negative electrode. For the first time the intercalation of (C2H5)4N+ into HOPG could be monitored by means of in situ atomic force microscopy (AFM). In analogy to the behavior in Li+ containing solution the formation of a surface film on the negative electrode could be detected. The question is addressed if this film might serve as a solid electrolyte interphase preventing sustained solvent decomposition. Keywords: Electrochemical in situ atomic force microscopy (AFM), Intercalation, Film formation, Tetraalkylammonium salt, Propylene carbonate decomposition, Electrochemical double layer capacitor (EDLC)

In situ electrochemical scanning tunneling microscopy (STM) has been applied to study the initial stages of hydroxide formation and its reduction on Co(0 0 0 1) in 0.1 M NaOH. XPS investigations give chemical information about the adlayer composition after oxidation and at the different reduction stages. In the subpotential range of oxidation at E At the very beginning of the reduction process small two-dimensional metal clusters and islands can be observed. It is assumed that they are crystallization nuclei for metal formation. They enlarge and grow together with other islands or larger terraces. During this reduction process two-dimensional adatomic arrays consisting of OH−–Co2+– OH− trimers appear on the surface. Some of these trimers accumulate at step edges, and finally decorate them. This decoration builds up an energy barrier for further metal incorporation and prevents further growth of the terraces with remaining metal clusters on their surfaces. The reduction of the Co(OH)2 layer is found to be not completed which is confirmed by XPS results.