Integrable systems on the sphere associated with genus three algebraic curves

New variables of separation for few integrable systems on the two-dimensional sphere with higher order integrals of motion are considered in detail. We explicitly describe canonical transformations of initial physical variables to the variables of separation and vice versa, calculate the corresponding quadratures and discuss some possible integrable deformations of initial systems.Comment: 19 pages, LaTeX with AMS font

Mn promotion of rutile TiO2-RuO2 anodes for water oxidation in acidic media

\u3cp\u3eA method to reduce noble metal content in oxygen-evolving electrocatalysts suitable to work in acidic media is presented. TiO\u3csub\u3e2\u3c/sub\u3e-RuO\u3csub\u3e2\u3c/sub\u3e anodes can be promoted by Mn, resulting in increased activity and stability. The most active composition displayed an overpotential of 386 mV at a current density of 10 mA cm\u3csup\u3e–2\u3c/sup\u3e, and a Tafel slope of 50 mV dec\u3csup\u3e–1\u3c/sup\u3e. This anode only included 17 at% Ru out of the total amount of metals included in the film. We investigated the influence of Mn addition to TiO\u3csub\u3e2\u3c/sub\u3e-RuO\u3csub\u3e2\u3c/sub\u3e on the structure, morphology, and surface area, and related differences to catalytic activity and stability. We found that increased porosity of the anode film by Mn addition and Mn inclusion in the TiO\u3csub\u3e2\u3c/sub\u3e-RuO\u3csub\u3e2\u3c/sub\u3e lattice can explain the enhanced catalytic activity. A detailed characterization of fresh and used anodes provided insight into structural modifications induced by electrochemical treatment.\u3c/p\u3

A Study of the Feasibility of Using Ammonium Sulfate in Copper—Nickel Ore Processing

The possibility of applying a combined concentration and metallurgical method for processing low-grade and refractory copper–nickel ores was considered. The resulting rougher and scavenger flotation concentrate contained 2.07% nickel and 0.881% copper at a recovery of 85.44% and 89.91%, respectively. The concentrate was then roasted with ammonium sulfate, followed by aqueous leaching of clinker to dissolve nickel and copper. The roasting temperature, the ratio of concentrate to (NH4)2SO4 in the mixture, and the temperature were varied. Based on the study findings, the following process conditions were found to be optimal: roasting temperature 400 °C, rougher concentrate to ammonium sulfate ratio 1:7, and grinding size −40 μm. A roasting temperature of 400 °C is significantly lower than the temperature applied in conventional pyrometallurgical processes. The possibility of collecting off-gases allows the reagent to be regenerated and makes the process even more cost-effective. End-to-end recovery into pregnant solution was 81.42% for nickel and 82.81% for copper. The resulting solutions can be processed by known hydrometallurgical methods

Efficient and highly transparent ultra-thin nickel-iron oxy-hydroxide catalyst for Oxygen evolution prepared by successive Ionic layer adsorption and reaction

NiFeOx thin films prepared by successive ionic layer adsorption and reaction (SILAR) were deposited onto nanostructured hematite (Fe2O3) photoanodes and their effect on the current density and photo‐onset potential was studied. After optimization of bath concentration, immersion times, and number of SILAR cycles, very conformal and active NiFeOx films with controlled Fe/Ni content ratios were obtained. Upon the incorporation of Fe2+ species in the NiCl2 solution bath, a cathodic shift in the overpotential required for the oxygen evolution reaction (OER) by more than 200 mV with no decrease in current density was observed after 40 SILAR cycles. We demonstrate that by fine‐tuning the film composition and thickness, NiFeOx can be employed as an efficient OER catalyst with very low absorbance in the visible spectrum. By doing so, we demonstrate that this material has great potential for incorporation in semiconductor photoelectrodes for direct solar‐driven water electrolysis. Being a simple water‐based layer‐by‐layer growth method, SILAR offers promise for the synthesis of catalyst coatings in nano‐structured and high surface area electrodes

Temperature-dependent kinetic studies of the chlorine evolution reaction over RuO2(110) model electrodes

\u3cp\u3eUltrathin single-crystalline RuO \u3csub\u3e2\u3c/sub\u3e(110) films supported on Ru(0001) are employed as model electrodes to extract kinetic information about the industrially important chlorine evolution reaction (CER) in a 5M concentrated NaCl solution under well-defined electrochemical conditions and variable temperatures. A combination of chronoamperometry (CA) and online electrochemical mass spectrometry (OLEMS) experiments provides insight into the selectivity issue: At pH = 0.9, the CER dominates over oxygen evolution, whereas at pH = 3.5, oxygen evolution and other parasitic side reactions contribute mostly to the total current density. From temperature-dependent CA data for pH = 0.9, we determine the apparent free activation energy of the CER over RuO \u3csub\u3e2\u3c/sub\u3e(110) to be 0.91 eV, which compares reasonably well with the theoretical value of 0.79 eV derived from first-principles microkinetics. The experimentally determined apparent free activation energy of 0.91 eV is considered as a benchmark for assessing future improved theoretical modeling from first principles. \u3c/p\u3

Rational Design of Fullerene Derivatives for Improved Stability of p-i-n Perovskite Solar Cells

Perovskite solar cells (PSCs) with p-i-n architecture attracted particular attention from the research community due to their simple and scalable fabrication at low temperatures. However, the operational stability of p-i-n PSCs has to be improved, which requires the development of advanced charge transport interlayers. Fullerene derivatives such as phenyl-C61-butyric acid methyl ester (PC61BM) are commonly used as electron transport layer (ETL) materials in PSCs, though they strongly compromise the device stability. Indeed, it has been shown that PC61BM films actively absorb volatile products resulting from photodegradation of lead halide perovskites and transport them towards top metal electrode. Thus, there is an urgent need for development of new fullerene-based electron transport materials with improved properties, in particular the ability to heal defects on the perovskite films surface and block the diffusion of volatile perovskite photodegradation products. To address this challenge, a systematic variation of organic addends structure should be performed in order to tailor the properties of fullerene derivatives. Herein, we rationally designed a series of fullerene derivatives with different side chains and explored their performance as ETL materials in perovskite solar cells. It has been shown that among all studied compounds, a methanofullerene with thiophene pendant group enables both high efficiency and improved device operational stability. The obtained results suggest that further engineering of fullerene-based materials could pave a way for the development of advanced ETL materials enabling long lifetimes of p-i-n perovskite solar cells

On the origin of the photocurrent of electrochemically passivated p-InP(100) photoelectrodes

\u3cp\u3eIII-V semiconductors such as InP are highly efficient light absorbers for photoelectrochemical (PEC) water splitting devices. Yet, their cathodic stability is limited due to photocorrosion and the measured photocurrents do not necessarily originate from H\u3csub\u3e2\u3c/sub\u3e evolution only. We evaluated the PEC stability and activation of model p-InP(100) photocathodes upon photoelectrochemical passivation (i.e. repeated surface oxidation/reduction). The electrode was subjected to a sequence of linear potential scans with or without intermittent passivation steps (repeated passivation and continuous reduction, respectively). The evolution of H\u3csub\u3e2\u3c/sub\u3e and PH\u3csub\u3e3\u3c/sub\u3e gases was monitored by online electrochemical mass spectrometry (OLEMS) and the Faradaic efficiencies of these processes were determined. Repeated passivation led to an increase of the photocurrent in 0.5 M H\u3csub\u3e2\u3c/sub\u3eSO\u3csub\u3e4\u3c/sub\u3e, while continuous reduction did not affect the photocurrent of p-InP(100). Neither H\u3csub\u3e2\u3c/sub\u3e nor PH\u3csub\u3e3\u3c/sub\u3e formation increased to the same extent as the photocurrent during the repeated passivation treatment. Surface analysis of the spent electrodes revealed substantial roughening of the electrode surface by repeated passivation, while continuous reduction left the surface unaltered. On the other hand, photocathodic conditioning performed in 0.5 M HCl led to the expected correlation between photocurrent increase and H\u3csub\u3e2\u3c/sub\u3e formation. Ultimately, the H\u3csub\u3e2\u3c/sub\u3e evolution rates of the photoelectrodes in H\u3csub\u3e2\u3c/sub\u3eSO\u3csub\u3e4\u3c/sub\u3e and HCl are comparable. The much higher photocurrent in H\u3csub\u3e2\u3c/sub\u3eSO\u3csub\u3e4\u3c/sub\u3e is due to competing side-reactions. The results emphasize the need for a detailed evaluation of the Faradaic efficiencies of all the involved processes using a chemical-specific technique like OLEMS. Photo-OLEMS can be beneficial in the study of photoelectrochemical reactions enabling the instantaneous detection of small amounts of reaction by-products.\u3c/p\u3

Electrochemical stability of RuO2(110)/Ru(0001) model electrodes in the oxygen and chlorine evolution reactions

\u3cp\u3eRuO \u3csub\u3e2\u3c/sub\u3e is commercially employed as an anodic catalyst in the chlor-alkali process. It is also one of the most active electrocatalysts for the oxidation of water, relevant to electrochemical water splitting. However, the use of RuO \u3csub\u3e2\u3c/sub\u3e is limited by its low anodic stability under acidic conditions, especially at high overpotentials. In the present work, the electrochemical stability of model RuO \u3csub\u3e2\u3c/sub\u3e(110)/Ru(0001) anodes was investigated in order to gain a deeper understanding of the relation between structure and performance in Cl \u3csub\u3e2\u3c/sub\u3e and O \u3csub\u3e2\u3c/sub\u3e evolution reactions (CER and OER, respectively). Online electrochemical mass spectrometry was used to determine the onset potential of CER and OER in HCl and H \u3csub\u3e2\u3c/sub\u3eSO \u3csub\u3e4\u3c/sub\u3e electrolytes, respectively. The onset potential of OER was higher in HCl than in H \u3csub\u3e2\u3c/sub\u3eSO \u3csub\u3e4\u3c/sub\u3e due to competition with the kinetically more favorable CER. A detailed stability evaluation revealed pitting corrosion of the electrode surface with exposure of Ru(0001) metal substrate concomitant with the formation of a hydrous RuO \u3csub\u3e2\u3c/sub\u3e in some areas regardless of the applied electrochemical treatment. However, despite local pitting, the RuO \u3csub\u3e2\u3c/sub\u3e(110) layer preserves its thickness in most areas. Degradation of the electrode was found to be less severe in 0.5 M HCl due to a decrease in the faradaic efficiency of RuO \u3csub\u3e2\u3c/sub\u3e oxidation caused by competition with the kinetically more favorable CER. \u3c/p\u3