Investigation of phosphate species adsorption/desorption processes was performed on Ag(100) and Ag(111) electrodes in H$_{3}$PO$_{4}$, KH$_{2}$PO$_{4}$ and K$_{3}$PO$_{4}$ solutions by Current-Potential ($j-V$) profiles and Electrochemical Impedance Spectroscopy ($EIS$). We used the equivalent circuit method to fit the impedance spectra. Different electrical equivalent circuits ($EECs$) were employed depending on the potential region that was analyzed. For potentials more negative than the onset of the hydrogen evolution reaction ($her$), a charge transfer resistance (R$_{ct}$) in parallel to the $(RC)$ branches was included. Peaks from $j-V$ profiles were integrated to estimate surface coverage. A reversible process was observed for Ag(hkl)/KH$_{2}$PO$_{4}$ systems, where a value of 0.07 ML was obtained. For Ag(111)/H$_{3}$PO$_{4}$, a coverage of about 0.024 ML was calculated from anodic/cathodic $j-V$ profiles, whereas for Ag(hkl)/K$_{3}$PO$_{4}$ systems different values were obtained from integration of anodic/cathodic peaks due to highly irreversible processes were observed. In the case of Ag(hkl)/K$_{3}$PO$_{4}$, the capacitance (C$_{(ϕ)}$) plots are well differentiated for the two faces, and co-adsorption of OH$^{-}$ was evaluated from resistance parameters. Characteristic face-specific relaxation times are obtained for each electrode. In addition, it was found that the onset potential of $her$ for Ag(111) at pH=1.60 was about 100 mV more negative compare to Ag(100).
Since the late 1960s, ceric hydrogen phosphates have attracted the attention of scientists due to remarkable ion exchange, sorption, proton-conduction and catalytic properties. In this work, through the application of various solvents, we, for the first time, have obtained monolithic aerogels based on ceric hydrogen phosphates with high porosity (~99%) and extremely low density (~10 microg/cm3). The composition and structure of aerogels were thoroughly studied with XRD, TEM, SEM, XPS, low temperature nitrogen adsorption methods, TGA/DSC, Fourier-transform infrared spectroscopy (FTIR) and small…
Density functional theory (DFT) has been used as an important tool for studying activity of oxygen reduction reaction (ORR) catalysts. The dispersion effects, which are not encountered in many of the previous DFT studies for periodic Pt(111), are scrutinized for their role in predicting ORR activity on Pt (111) surface. Spin orbit coupling is employed to account for relativistic effects expected for heavy metal platinum, which has not been addressed in any of the previous studies on Pt(111). Adsorption behavior of intermediates and free energy changes of elementary reactions of ORR are analyze…
Co(II) dissolved in acetate buffer at pH 7 is found to be a good water oxidation catalyst (WOC) showing electrocatalytic water oxidation current significantly greater than Co(II) in phosphate buffer under the same conditions owing to the higher solubility of the former. When electrodeposited on ITO/FTO electrodes it forms acetate bound cobalt(II)oxide based material (Co-Ac-WOC) showing catalytic water oxidation current density of 0.1 mA/cm$^{2}$ at 830 mV and 1 mA/cm$^{2}$ at 1 V in a pH 7 buffer solution. The morphology of Co-Ac-OEC is investigated with AFM, HR-TEM and SEM (at different times…
To understand the role of phosphate ester dispersant, we investigated the rheology of a BaTiO$_3$ slurry. For the model case, a coarse-grain molecular dynamics (CGMD) simulation was performed with the butyral polymer didodecyl hydrogen phosphate (DHP), in the toluene/ethanol solvent. By systematically analyzing the effect of DHP from an atomic-scale first principle and from all-atom MD to micro-scale CGMD simulation, we investigated how the adsorption of a DHP dispersant on a BaTiO$_3$ surface affects the microstructure rheology of a BaTiO$_3$ slurry. The first-principle and all-atom MD simula…
Spin-lattice coupling enables adaptive adsorption in magnetically-driven electrocatalysts
CNRS, Univ. Rennes, Institut de Physique de Rennes（法国国家科学研究中心，雷恩大学，雷恩物理研究所）；Institute of Chemical Research of Catalonia (ICIQ-CERCA), The Barcelona Institute of Science and Technology (BIST)（加泰罗尼亚化学研究学院（ICIQ-CERCA），巴塞罗那科学技术学院（BIST））；Catalan Institute of Nanoscience and Nanotechnology (ICN2), CSIC, Barcelona Institute of Science and Technology（加泰罗尼亚纳米科学与技术研究所（ICN2），西班牙国家科学研究委员会，巴塞罗那科学技术学院）；Departament de Química Física i Inorgànica, Universitat Rovira i Virgili（罗维拉-依吉利拉大学，物理与无机化学系）；European Synchrotron Radiation Facility（欧洲同步辐射装置）；ICREA（加泰罗尼亚卓越研究员学院）；CNRS, Univ Rennes, DYNACOM (Dynamical Control of Materials Laboratory) - IRL2015, The University of Tokyo（法国国家科学研究中心，雷恩大学，材料动力学控制实验室（IRL2015），东京大学）；Institute of Advanced Materials (INAM) Universitat Jaume I（豪梅一世大学，先进材料研究所（INAM））
Electrocatalytic hydrogen evolution reaction (HER) in alkaline media is a promising electrochemical energy conversion strategy. Ruthenium (Ru) is an efficient catalyst with a desirable cost for HER, however, the sluggish H2O dissociation process, due to the low H2O adsorption on its surface, currently hampers the performances of this catalyst in alkaline HER. Herein, we demonstrate that the H2O adsorption improves significantly by the construction of Ru-O-Mo sites. We prepared Ru/MoO2 catalysts with Ru-O-Mo sites through a facile thermal treatment process and assessed the creation of Ru-O-Mo i…
The extent of irreversible deactivation of Pt towards hydrogen oxidation reaction (HOR) due to sulfur adsorption and subsequent electrochemical oxidation is quantified in a functional PEM fuel cell. At 70 °C, sequential hydrogen sulfide (H2S) exposure and electrochemical oxidation experiments indicate that as much as 6% of total Pt sites are deactivated per monolayer sulfur adsorption at open circuit potential of a PEM fuel cell followed by its removal. The extent of such deactivation is much higher when the electrode is exposed to H2S when the fuel cell is operating at a finite load, and is d…
To satisfy rising energy needs and to handle the forthcoming worldwide climate transformation, major research attention has been drawn to environmentally friendly, renewable, and abundant energy resources. Hydrogen plays an ideal and significant role is such resources, due to its non-carbon-based energy and production through clean energy. In this work, we have explored the catalytic activity of a newly predicted haeckelite boron nitride quantum dot (haeck-BNQD), constructed from the infinite BN sheet, for its utilization in hydrogen production. Density functional theory calculations are emplo…
The hydrogen evolution reaction (HER) is a key process in electrochemical water splitting. To lower the cost and environmental impact of this process, it is highly motivated to develop electrocatalysts with low or no content of noble metals. Here we report on a novel and ingenious synthesis of hybrid PtxNi1-x electrocatalysts in the form of a nanoparticle-necklace structure named nanotrusses, with very low noble metal content. The nanotruss structure possesses important features, such as good conductivity, high surface area, strong interlinking and substrate adhesion, which renders for an exce…
In conventional chemisorption model, the d-band center theory (augmented sometimes with the upper edge of d-band for imporved accuarcy) plays a central role in predicting adsorption energies and catalytic activity as a function of d-band center of the solid surfaces, but it requires density functional calculations that can be quite costly for large scale screening purposes of materials. In this work, we propose to use the d-band width of the muffin-tin orbital theory (to account for local coordination environment) plus electronegativity (to account for adsorbate renormalization) as a simple se…
Molybdenum sulfide (MoS$_2$) has attracted significant attention due to its great potential as a low-cost and efficient catalyst for the hydrogen evolution reaction. Developing a facile, easily upscalable, and inexpensive approach to produce catalytically active nanostructured MoS$_2$ with a high yield would significantly advance its practical application. Colloidal synthesis offers several advantages over other preparation techniques to overcome the low reaction yield of exfoliation and drawbacks of expensive equipment and processes used in chemical vapor deposition. In this work, we report a…
Awakening catalytically active surface of BaRuO3 thin film for alkaline hydrogen evolution
Sungkyunkwan University（成均馆大学）；University of Cologne（科隆大学）；Gachon University（嘉泉大学）；Gyeongbuk Science & Technology Promotion Center, Gumi Electronics & Information Technology Research Institute（庆北科技促进中心，龟尾电子信息技术研究所）；Korea Basic Science Institute（韩国基础科学研究所）；Pukyong National University（釜庆国立大学）；Xi’an Jiaotong-Liverpool University（西交利物浦大学）
