Ruthenium Phosphide Synthesis and Electroactivity toward Oxygen Reduction in Acid Solutions

Ruthenium phosphides are known to be highly stable and conductive materials. A new process was developed to prepare ruthenium phosphide catalysts for oxygen reduction in acid solutions. Several synthesis methods have been applied to form pure RuP and Ru₂P as well as mixed phases of Ru and Ru_<i>x</i>P (<i>x</i> ≥ 1). These methods utilize high-temperature solid-state synthesis and reaction under autogenic pressure at elevated temperature (RAPET). On the basis of rotating ring–disk electrode (RRDE) experiments, oxygen reduction activity was observed on all Ru_<i>x</i>P materials. Characteristic kinetic parameters show specific exchange current densities in the range of 0.4–1.4 mA mg^–1, Tafel slopes of 129–135 mV dec^–1, and %H₂O₂ of 3–11% of the total current. Complementary XPS and Raman spectral analysis reveals a highly oxidized surface with significant presence of PO₄^3– and RuO₂ species. To the best of our knowledge, this is the first report identifying oxygen reduction activity on Ru_<i>x</i>P

Exceptionally Active and Stable Spinel Nickel Manganese Oxide Electrocatalysts for Urea Oxidation Reaction

Spinel nickel manganese oxides, widely used materials in the lithium ion battery high voltage cathode, were studied in urea oxidation catalysis. NiMn₂O₄, Ni_1.5Mn_1.5O₄, and MnNi₂O₄ were synthesized by a simple template-free hydrothermal route followed by a thermal treatment in air at 800 °C. Rietveld analysis performed on nonstoichiometric nickel manganese oxide-Ni_1.5Mn_1.5O₄ revealed the presence of three mixed phases: two spinel phases with different lattice parameters and NiO unlike the other two spinels NiMn₂O₄ and MnNi₂O₄. The electroactivity of nickel manganese oxide materials toward the oxidation of urea in alkaline solution is evaluated using cyclic voltammetric measurements. Ni_1.5Mn_1.5O₄ exhibits excellent redox characteristics and lower charge transfer resistances in comparison with other compositions of nickel manganese oxides and nickel oxide prepared under similar conditions.The Ni_1.5Mn_1.5O₄modified electrode oxidizes urea at 0.29 V versus Ag/AgCl with a corresponding current density of 6.9 mA cm^–2. At a low catalyst loading of 50 μg cm^–2, the urea oxidation current density of Ni_1.5Mn_1.5O₄ in alkaline solution is 7 times higher than that of nickel oxide and 4 times higher than that of NiMn₂O₄ and MnNi₂O₄, respectively

Vertically Aligned Nitrogen-Doped Carbon Nanotube Carpet Electrodes: Highly Sensitive Interfaces for the Analysis of Serum from Patients with Inflammatory Bowel Disease

The number of patients suffering from inflammatory bowel disease (IBD) is increasing worldwide. The development of noninvasive tests that are rapid, sensitive, specific, and simple would allow preventing patient discomfort, delay in diagnosis, and the follow-up of the status of the disease. Herein, we show the interest of vertically aligned nitrogen-doped carbon nanotube (VA-NCNT) electrodes for the required sensitive electrochemical detection of lysozyme in serum, a protein that is up-regulated in IBD. To achieve selective lysozyme detection, biotinylated lysozyme aptamers were covalently immobilized onto the VA-NCNTs. Detection of lysozyme in serum was achieved by measuring the decrease in the peak current of the Fe­(CN)₆^3–/4– redox couple by differential pulse voltammetry upon addition of the analyte. We achieved a detection limit as low as 100 fM with a linear range up to 7 pM, in line with the required demands for the determination of lysozyme level in patients suffering from IBD. We attained the sensitive detection of biomarkers in clinical samples of healthy patients and individuals suffering from IBD and compared the results to a classical turbidimetric assay. The results clearly indicate that the newly developed sensor allows for a reliable and efficient analysis of lysozyme in serum