Revealing the Synergy of Cation and Anion Vacancies on Improving Overall Water Splitting Kinetics

The exact understanding for each promotional role of cation and anion vacancies in bifunctional water splitting activity will assist in the development of an efficient activation strategy of inert catalysts. Herein, systematic first-principles computations demonstrate that the synergy of anion–oxygen and cation–manganese vacancies (V_O and V_Mn) in manganese dioxide (MnO₂) nanosheets results in abnormal local lattice distortion and electronic modulation. Such alterations enrich the accessible active centers, increase conductivity, enhance the water dissociation step, and favor intermediate adsorption–desorption, consequently promoting HER and OER kinetics. As proof of concept, robust electrocatalysts, MnO₂ ultrathin nanosheets doped with dual vacancies (DV–MnO₂) are obtained via a maturely chemical strategy. Detailed characterizations confirm the cation vacancies-V_Mn contribute to enhanced conductivity and anion vacancies-V_O enrich the active centers with optimized local electronic configurations, consistent with the simulative predictions. As expected, DV–MnO₂ exhibits exceptional bifunctionality with the strong assistance of synergetic dual vacancies which act as abundant “hot spots” for active multiple intermediates. Leading to a lower cell voltage (1.55 V) in alkali electrolyte is required to reach 10 mA cm⁻² for the overall water splitting system. These atomic-level insights on synergetic DV can favor the development of activating strategy from inert electrocatalysts.     

An Apparatus for Automated Cross Flow Solute Permeation Characterization of Membranes

Abstract

An apparatus is described for the automated characterization of ultrafiltration membranes using solute permeation in cross flow mode. The automated characterization approach described in this work lends itself well for the purpose of increased productivity and reducing operator fatigue/error. The operational, control, and data acquisition aspects of an automated membrane cross flow test unit, which are accomplished using LabVIEW 5.0? are described. The interpretation of the flux and separation data is independent of the apparatus and depends on the filtration regime and various theoretical models available. The apparatus can be used for reverse osmosis, nanofiltration, or ultrafiltration experiments, with appropriate selection of test cells and pumps.     

A New Type of Carbon Resistance Thermometer with Excellent Thermal Contact at Millikelvin Temperatures

Using a new brand of commercially available carbon resistor we built a cryogenic thermometer with an extremely good thermal contact to its thermal environment. Because of its superior thermal contact the thermometer is insensitive to low levels of spurious radio frequency heating. We calibrated our thermometer down to 5 mK using a quartz tuning fork He-3 viscometer and measured its thermal resistance and thermal response time.     

Actuation behavior of ionic polymer-metal composite based actuator in blood analogue fluid environment

ABSTRACT

In this paper, we have studied the actuation performance of Ionic Polymer Metal Composite based actuator (IPMC) in the artificial blood analogue fluid medium. The fluid used in this study was transparent and made from readily available materials. This study can be useful for testing the actuation behavior of IPMC by forming an in-vitro hemodynamic environment for treating different cardiovascular diseases. IPMC electrodes fabricated by a standard electroless deposition process. A rectangular strip of 35 mm length and 2 mm width was used for actuation testing under 0–5 V DC. Actuation results show fairly effective results in a fluid environment for repetitive measurements.     

High temperature steam gasification of wastewater sludge

High temperature steam gasification is one of the most promising, viable, effective and efficient technology for clean conversion of wastes to energy with minimal or negligible environmental impact. Gasification can add value by transforming the waste to low or medium heating value fuel which can be used as a source of clean energy or co-fired with other fuels in current power systems. Wastewater sludge is a good source of sustainable fuel after fuel reforming with steam gasification. The use of steam is shown to provide value added characteristics to the sewage sludge with increased hydrogen content as well total energy. Results obtained on the syngas properties from sewage sludge are presented here at various steam to carbon ratios at a reactor temperature of 1173 K. Effect of steam to carbon ratio on syngas properties are evaluated with specific focus on the amounts of syngas yield, syngas composition, hydrogen yield, energy yield, and apparent thermal efficiency. The apparent thermal efficiency is similar to cold gas efficiency used in industry and was determined from the ratio of energy in syngas to energy in the solid sewage sludge feedstock. A laboratory scale semi-batch type gasifier was used to determine the evolutionary behavior of the syngas properties using calibrated experiments and diagnostic facilities. Results showed an optimum steam to carbon ratio of 5.62 for the range of conditions examined here for syngas yield, hydrogen yield, energy yield and energy ratio of syngas to sewage sludge fuel. The results show that steam gasification provided 25% increase in energy yield as compared to pyrolysis at the same temperature.     

Use of membranes for energy efficient concentration of dilute streams

In the chemical-process industries, dilute streams containing valuable ingredients are generated in several unit operations. Mechanical vapor-recompression is the best available technology for vaporization that may be used for concentrating such dilute solutions. Energy consumption for vaporization by compression and membrane technology is 350 and 90 kJ/kg, respectively. In order to save additional energy by recycling water, this study explored the use of membranes for processing a hot feed (70–80°C) containing small amounts of food ingredients. Pilot tests report the effects of experimental parameters on membrane performance. The impact of pretreatment of the feed and membrane-cleaning procedures to maintain performance will also be discussed. Initial results indicate that the use of a membrane to pre-concentrate, prior to the final concentration with mechanical vapor recompression, has the potential to save significant amounts of energy. Furthermore, the use of membranes would increase plant capacity by reducing the load on the vapor-compression unit. In this study, it was estimated that a plant processing 15 metric tonnes of feed every day and using membrane technology for concentrating to twice the concentraiton would save about 2 GJ of energy.