Temperature-dependent state of hydrogen molecules within the nanopore of multi-walled carbon nanotubes

In observation of the state of hydrogen molecules within the carbon nanopore, the excess adsorption amounts of hydrogen on the multi-walled carbon nanotubes (MWCNTs) were measured at equilibrium pressure–temperatures from 0.1 to $\text{12.3}\text{MPa}$ and 123 to $\text{310}\text{K}$. The principles of thermodynamic equilibrium and a higher order Virial adsorption coefficient were applied to determining the maximum surface coverage of hydrogen molecules on the adsorbent surface. The thermodynamic equilibrium-based adsorption model was linearized to estimate the interaction energy among the adsorbed hydrogen molecules at each adsorption equilibrium state. The results demonstrate that the interaction energies among adsorbed hydrogen molecules are positive in the lower temperature region $\text{(<200}\text{K}\text{)}$ and reach the maximum value around a temperature from 160 to $\text{180}\text{K}$. However, it will gradually be negative when the temperature is approaching $\text{230}\text{K}$. In other words, the confined hydrogen molecules repulse each other in the low-temperature environment while they attract each other at the ambient temperature. It implies that the dissociativeness of hydrogen occurred in the experimental pressure–temperature range, and it is also suggested that the temperature between 160 and $\text{180}\text{K}$ could be a preferable condition to make full use of physical and chemical adsorption of hydrogen molecules on the adsorbent.     

Spectroscopic identification of a novel catalytic reaction of potassium and atomic hydrogen and the hydride ion product

From a solution of a Schrödinger-type wave equation with a nonradiative boundary condition based on Maxwell's equations, Mills predicts that atomic hydrogen may undergo a catalytic reaction with certain atomized elements and ions which singly or multiply ionize at integer multiples of the potential energy of atomic hydrogen, $\text{27.2}\text{eV}\text{(m×27.2}\text{eV}$, wherein m is an integer). The reaction involves a nonradiative energy transfer to form a hydrogen atom that is lower in energy than unreacted atomic hydrogen with the release of energy. One such atomic catalytic system involves potassium atoms. The first, second, and third ionization energies of potassium are 4.34066, 31.63, and $\text{45.806}\text{eV}$, respectively. The triple ionization reaction of K to K³⁺, then, has a net enthalpy of reaction of $\text{81.7766}\text{eV}$, which is equivalent to $\text{3×27.2}\text{eV}$. Intense extreme ultraviolet (EUV) emission was observed from incandescently heated atomic hydrogen and the atomized potassium catalyst that generated an anomalous plasma at low temperatures (e.g. $\text{≈10}{}^3\text{K}$) and an extraordinary low field strength of about 1–$\text{2}\text{V/cm}$. No emission was observed with potassium or hydrogen alone or when sodium replaced potassium with hydrogen. Emission was observed from K³⁺ that confirmed the resonant nonradiative energy transfer of $\text{3×27.2}\text{eV}$ from atomic hydrogen to atomic potassium. The catalysis product, a lower-energy hydrogen atom, was predicted to be a highly reactive intermediate which further reacts to form a novel hydride ion. The predicted hydride ion of hydrogen catalysis by atomic potassium is the hydride ion H⁻(1/4). This ion was observed spectroscopically at $\text{110}\text{nm}$ corresponding to its predicted binding energy of $\text{11.2}\text{eV}$.     

Growing stock-based forest biomass estimate for India

The total standing biomass (including above ground and below ground) in Indian forests for the year 1992–93 was estimated using information on state and union-territory field inventory based growing stock volume and the corresponding area under three different crown density classes (very dense forests with crown cover 70 percent and above, dense forest with crown cover 40 percent but <70 percent and open forests with crown cover between 10 and 40 percent) grouped under four major forest categories (hardwood, spruce-fir, pine and bamboo) by Forest Survey of India. The growing stock volume was converted to total biomass using biomass expansion factors as function of growing stock volume density. The average growing stock volume density in Indian forests for the study year 1992–93 was $\text{74.42}\text{m}{}^3\text{ha}{}^{\mathrm{-1}}$ but it varied amongst states, with a range of $\text{7.1}\text{m}{}^3\text{ha}{}^{\mathrm{-1}}$ in Punjab to $\text{224.5}\text{m}{}^3\text{ha}{}^{\mathrm{-1}}$ in Jammu and Kashmir. The total standing biomass (above ground and below ground) was estimated as $\text{8683.7}\text{Mt}\text{(}\text{Mt}\text{=10}{}^{12}\text{g}\text{)}$. The aboveground and belowground biomass was estimated as 6865.1 and $\text{1818.7}\text{Mt}$, contributing 79 and 21 percent to the total biomass, respectively. The mean biomass density in Indian forests was estimated as $\text{135.6}\text{t}\text{ha}{}^{\mathrm{-1}}$ and amongst the states it varied from $\text{27.4}\text{t}\text{ha}{}^{\mathrm{-1}}$ in Punjab to $\text{251.8}\text{t}\text{ha}{}^{\mathrm{-1}}$ in Jammu and Kashmir, respectively. The estimates have been compared with previous studies, which had estimated biomass in the range of 4400–$\text{8700}\text{Mt}$ for the corresponding period. Our results are an improvement over previous estimates as these incorporate biomass expansion factors which relate wood volume to biomass as a function of growing stock volume density, four forest types and three crown density classes of Indian forests. These improved biomass estimates are crucial to assess the total C pool of forests and further for use as inputs to models to estimate net C flux to atmosphere from Indian forests due to deforestation and landuse changes.     

Electrochemical performance of hydrogen evolution reaction of Ni–Mo electrodes obtained by mechanical alloying

Electro active Ni–Mo electrodes have been prepared by mechanical alloying and pressure-less sintering $\text{(1173}\text{K}\text{)}$ Ni and Mo powders. The electrochemical performance of obtained electrodes has been evaluated in KOH 30% at $\text{343}\text{K}$ as a function of the milling time, applied pressure for green compaction as well as the effect conferred by the addition of a process control agent (PCA). Cathodic slope of the best specimen is $\text{279}\text{mV}\text{/}\text{dec}$. Faster reaction kinetics is observed for the specimens treated with PCA addition. The longer milling time and applied pressure on the specimens the better cathodic response. The activation overpotential, i.e. cathodic-Tafel slopes found at high overvoltages are in the range of 274–$\text{481}\text{mV}\text{/}\text{dec}$, whereas the exchange current density for the hydrogen evolution reaction ranged from 27.3 to $\text{1.4}\text{mA}\text{/}\text{cm}{}^2$.     

Continuous fermentative hydrogen production from sucrose and sugarbeet

To produce hydrogen by fermentation of biomass, a continuous process using a non-sterile substrate with a readily available mixed microflora is desirable. This work investigates a simple batch start-up procedure at pH 5.2 and 32°C, using anaerobically digested sewage sludge, and continuous hydrogen production from refined sucrose, pulped sugarbeet and a water extract of sugarbeet. Without heat treating the sludge, and with initial nitrogen sparging, a hydrogen producing culture was established within 5 days and remained stable during two experiments of 45 and 32 days duration. At 14–$\text{15}\text{h}$ retention time ($\text{16}\text{kg}$ total sugar $\text{m}{}^{\mathrm{-3}}\text{d}{}^{\mathrm{-1}}$ organic loading rate) hydrogen yields for refined sucrose and pulped sugarbeet were, respectively, 1.0±0.1 and $\text{0.9±0.2}\text{mol}\text{/}\text{mol}$ hexose converted. With nitrogen sparging hydrogen yields were 1.7±0.2–1.9±0.2 and $\text{1.7±0.2}\text{mol}$/mol hexose converted for refined sucrose and water extract of sugarbeet, respectively. Increasing ethanol concentration during operation on sugarbeet, and in some cases a higher redox potential $\text{(>−150}\text{mV}\text{)}$, correlated with lower hydrogen yield.     

Biological production of hydrogen from glucose by natural anaerobic microflora

Palm oil mill effluent (POME) sludge, sludge compost from Malaysia and CREST compost from Philippines were collected for the study. The capability of these microflora to produce hydrogen was examined with $\text{500}\text{ml}$ artificial wastewater containing 1% glucose, 0.2% yeast extract and 0.018% magnesium chloride hexahydrate under anaerobic fermentation in a batch culture. The microflora in POME sludge, sludge compost and CREST compost were found to produce significant amounts of hydrogen. The maximum production yield of hydrogen per decomposed glucose was $\text{2.1}\text{mol}\text{/}\text{mol}$-glucose at a conversion rate of $\text{0.137}\text{L}\text{/(}\text{L-med}\text{h}\text{)}$ at 50°C obtained by sludge compost. All fermentations were carried out without pH control. It was also found that the addition of nitrogen source in the medium caused a change in hydrogen produced. There was no methane gas in the evolved gas.     

Hydrogen production by Clostridium thermolacticum during continuous fermentation of lactose

In the production of acetate by Clostridium thermolacticum growing on lactose, considerable amounts of hydrogen were generated. Lactose available in large amounts from milk permeate, a wastestream of the dairy industry, appears to be a valuable substrate for cheap production of biohydrogen.In this study, continuous cultivation of C. thermolacticum was carried out in a bioreactor, under anaerobic thermophilic conditions, on minimal medium containing $\text{10}\text{g}\text{l}{}^{\mathrm{-1}}$ lactose. Different dilution rates and pH were tested.C. thermolacticum growing on lactose produced acetate, ethanol and lactate in the liquid phase. For all conditions tested, hydrogen was the main product in the gas phase. Hydrogen specific production higher than $\text{5}\text{mmol}$ H₂ ($\text{g}\text{cell}\text{)}{}^{\mathrm{-1}}\text{h}{}^{\mathrm{-1}}$ was obtained. By operating this fermentation at high-dilution rate and alkaline pH, the hydrogen content in the gas phase was maximized.