Synthesis of Intercalation Compounds in the Graphite–HNO3–H3PO4System

The highly oriented pyrolytic graphite–HNO₃–H₃PO₄system was studied by x-ray diffraction and potentiometry at different acid concentrations. The results demonstrate that chemical and electrochemical intercalation in the graphite–98% HNO₃–85% H₃PO₄system yields graphite nitrate, a binary graphite intercalation compound (GIC). H₃PO₄is shown to have an ambiguous effect on the concentration ranges of different stages of graphite nitrate, shifting them to lower HNO₃concentrations as compared to the graphite–HNO₃–H₂O system. In the graphite–98% HNO₃–100% H₃PO₄system, a stage II ternary GIC is obtained, with an intercalate layer thickness d _i 4.7 Å. Stages II–VI of this GIC were prepared via exchange reaction between graphite nitrate and 100% H₃PO₄. A mechanism for the formation of the ternary GIC is proposed. The synthesis of the cointercalated GIC is likely to involve two steps: in the first step, graphite nitrate is formed; subsequent reaction in the intercalate layer leads to partial replacement of solvated HNO₃by H₃PO₄molecules.     

Surface modification of carbon fibers with nitric acid solutions

We have studied the surface modification of carbonized carbon fibers with nitric acid solutions, compared the effects of 60 and 98% HNO₃, and examined the influence of the anodic polarization of the fiber for surface functionalization. Unmodified and surface-modified carbon fibers have been characterized by a variety of physicochemical techniques.     

CuBr2‐induced charge screening on photoactive nanocolloidal polypyrrole:poly(styrene sulfonate) composite multilayer thin‐film counter electrodes for high‐efficiency dye‐sensitized solar cells

Nanocolloidal polypyrrole (PPy):poly(styrene sulfonate) (PSS) particles were synthesized by chemical oxidative polymerization using 15 wt% of PSS. The highly processable polymer composite (PPy:PSS) was spin‐coated at 4000 rpm on fluorine‐doped tin oxide glass and subsequently employed as a counter electrode (CE) for dye‐sensitized solar cells (DSCs). PPy:PSS multilayer (one, three, five) CEs were treated with CuBr₂ salt, which enhances the efficiency of the DSCs. Optical studies reveal that a bulkier counterion hinders interchain interactions of PPy which on salt treatment shows a moderate redshift in absorption maxima. Salt‐treated PPy:PSS films exhibit lower charge transfer resistance, higher surface roughness and better catalytic performance for the reduction of I₃^?, when compared with untreated films. The improved catalytic performance of salt‐treated PPy:PSS multilayer films is attributed to charge screening and conformational change of PPy, along with the removal of excess PSS. Under standard AM 1.5 sunlight illumination, salt treatment is shown to boost the efficiency of multilayer PPy:PSS composite film‐based DSCs, leading to enhanced power conversion efficiency of 6.18, 6.33 and 6.37% for one, three and five layers, respectively. These values are significantly higher (ca 50%) than those for corresponding devices without CuBr₂ salt treatment (3.48, 2.90 and 2.01%, respectively). © 2016 Society of Chemical Industry     

Temperature and Time Effects on the Acid Corrosion of Steel in the Presence of Acetylenic Inhibitors

Potentiostatic and gravimetric methods were used to reveal that the inhibition effect of acetylenic inhibitors (namely propargyl alcohol and propargyl chloride) on the electrode processes of iron and steel corrosion in hydrochloric and sulfuric acids grows with time and temperature, owing to the formation of a polymeric film on the metal surface. In sulfuric acid, propargyl alcohol is easily hydrogenated to give removable reduction products, which lowers its protection effect on steel corrosion.     

Convective Factor in the Net Current of Iron Cathode in Sulfuric and Hydrochloric Solutions with Propargyl Alcohol and Propargyl Chloride

Net cathodic current decreases in solutions of hydrochloric and especially sulfuric acids with an increase in the rotational speed of the iron disc cathode or the content of propargyl alcohol (PA) or propargyl chloride (PC). The two compounds, especially PA, are hydrolyzed following mixed kinetics.