Highly active and stable bi-functional NiCoO2 catalyst for oxygen reduction and oxygen evolution reactions in alkaline medium

Single step solution combustion technique was used to synthesize NiO, Co₃O₄ and NiCoO₂ mixed metal oxide with good crystallinity and uniform properties. XRD spectrum indicates the existence of cubic NiCoO₂ phase without any impurities. SEM results indicate the presence of porous structures in all the three cases, a typical characteristic of combustion synthesized samples, which is due to the evolution of gases during the synthesis process. TEM along with the phase mapping shows the presence of well dispersed elements Ni, Co and O throughout the sample. All the three catalysts were evaluated for their bifunctionality towards oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) in alkaline medium. NiCoO₂ shows the highest number of electron transfer in the overall reaction mechanism with the maximum kinetic current density of 12.3 mA/cm². The kinetics of NiCoO₂ towards ORR and OER was analyzed using Tafel plot and compared with the mono-metal oxides. The catalytic stability was evaluated for 24 h using continuous chronoamperometric (CA) runs, where NiCoO₂ shows exceptionally stable performance without any significant decay in current. The highest activity of NiCoO₂ could be due to the presence of higher oxidation states of Ni and Co and because of the existence of the oxygen defects acting as active sites for the oxygen adsorption/desorption during the electrocatalytic reactions. Based on the activity and stability trends, NiCoO₂ is found to be a promising bifunctional oxygen electrocatalyst for long-term applications.     

An optimization method to find the thermodynamic limit on enhancement of solar thermal decomposition of methane

An optimization approach to enhancing the solar thermal decomposition of methane (TDM) reaction process based on the fluid flow pattern reconstruction is proposed. The sum of entropy generations due to TDM reaction and heat convection in the process is shown to tend to its maximum when the performance of the reaction is enhanced, and thus, is used as the criterial to optimize the velocity field of the fluid. This optimization problem is solved by the calculus of variations method. The obtained flow pattern is shown to be able to give the conditions to achieve the optimally enhanced TDM process. As the sum of the entropy generations tends to its extremum, the solution found by the optimization can be known as the thermodynamic limit for the TDM process enhancement. The obtained flow pattern can then be used to inspire the design of internal structures of the solar TDM reactor.     

Effect of introducing a steam pipe to n-dodecane decomposition by in-liquid plasma for hydrogen production

A method has been developed to improve the hydrogen production efficiency (HPE) by in-liquid plasma n-dodecane decomposition. A thin steam pipe is placed over the plasma electrode to recover the thermal energy emitted from the plasma to its surroundings. The steam generated by this energy is supplied to the vaporized n-dodecane around the edge of the plasma to cause a steam reforming reaction (SRR). Water pyrolysis is suppressed by not supplying the steam directly to the plasma. A large amount of CO and a small amount of CO₂ were detected in the produced gas. This indicates that a strong SRR has occurred. The HPE obtained by this method is 0.28 Nm³/kWh, which is two times greater than those obtained by previous methods, and similar to or greater than the yield of water electrolysis. This result is a major advance in the field of plasma heavy hydrocarbon decomposition aimed at hydrogen production. HPE is expected to be further improved by simply increasing the input power, due to synergy between the heat recovery effect of the steam pipe and the bubble stabilization effect. This indicates that this method has a high potential.     

Protium removal from deuterium-tritium mixture with displacement chromatography method: Experiments and simulations

The displacement chromatography technique with a tri-column system was used to reduce the protium (H) in the deuterium-tritium (D-T) mixture, and the separation performance was studied numerically by ANSYS FLUENT. The experimental results showed that the isotopic abundance of H in the D-T mixture dropped from 2.7% to an acceptable level of 0.88%. The simulation results showed that a lower porosity (θ) of the filling material made a higher separation factor, but a lower separation efficiency. The velocity of the product gas at the outlet of the separation column approximately had a linear relationship with θ^5/3/(1-θ)², which partly indicated the pore diffusion resistance. The mixed gas could contact the filling materials more sufficiently under a lower flow rate resulting in a lower protium concentration in the product gas. The separation column with a thin and long shape had a better separation performance and a lower product gas loss.     

Ultra-small RuPx nanoparticles on graphene supported schiff-based networks for all pH hydrogen evolution

As a promising candidate to replace Pt in hydrogen evolution reaction (HER), ruthenium phosphide catalysts have shown excellent performance and attract increasing attention. However, it is still a challenge to control the particle sizes of RuP_x were on the supports. In this study, the Schiff-based networks with 3D rigid organic networks are successfully grown on graphene, and the obtained composite was used as a new support for the RuP_x. This composite can not only provide more metal coordinating sites but also restrict the growth of RuP_x. Therefore, ultra-small RuP_x nanoparticles are uniformly dispersed via a subsequent phosphating and pyrolysis process. The final RuP_x/NPG catalyst exhibits low overpotentials at the current density of 10 mA cm⁻² (32 mV in 0.5 M H₂SO₄ solution, 13 mV in 1 M KOH solution, and 50 mV in 1 M PBS solution). This work provides a new strategy to solve the aggregation problem of the metal phosphides on the substrate by introducing Schiff-based networks into the graphene.     

Facial synthesis of dandelion-like g-C3N4/Ag with high performance of photocatalytic hydrogen production

Nowadays, energy shortage is one of the major problems in the world. Photocatalytic hydrogen production is a new type of energy technology with good application prospect. As a new type of photocatalytic semiconductor material, g-C₃N₄ has attracted much attention as a photocatalyst. By ultrasonic treatment of a mixed solution of g-C₃N₄ and bovine serum albumin, followed by adding a certain amount of silver nitrate solution and then directly hydrothermal treatment, a special dandelion-like g-C₃N₄/Ag (D-g-C₃N₄/Ag) was prepared. The scanning electronic microscopy, transmission electronic microscopy, X-ray diffraction, Fourier transform infrared, fluorescence and physicochemical adsorption methods were used to characterize the morphology and structure of D-g-C₃N₄/Ag. In addition, the photocatalytic H₂ production of D-g-C₃N₄/Ag with different Ag loadings or in different sacrificial agents and different pH conditions were investigated. The results indicated that when triethanolamine was used as sacrificial agent, photocatalytic hydrogen efficiency was the best, and the rate of photocatalytic hydrogen production reached 862 μmol g⁻¹ h^{− 1} as the Ag loading was 4%.     

Pre-service teachers’ behavioral intention to make educational animated movies and their experiences

Educational animated movies are one of the most entertainment format to deliver any educational messages. These movies can be used a wide range of educational subject areas such as science, engineering and daily life skills procedures. The purpose of this study is to determine the behavioral intention of pre-service teachers while preparing educational animated movies, the factors influencing such behavioral intention, and their experiences. The sample consists of 98 (52 males and 46 females) pre-service teachers studying Department of Computer Education and Instructional Technology. As data collection tools, two different scales were used in order to determine the levels of attitude of the pre-service teachers towards making animated movies and their experiences such as their cooperative communication levels, levels of enjoyment and having difficulty. They prepared the animated movies for class use during five weeks. According to the findings, they were willing to make animated movies in their future lessons. In addition, they enjoyed it, did not experience much difficulty, and engaged in cooperative communication with one another. Performance expectancy was seen to have the highest mean and to have a significant influence on behavioral intention. This research is significant because process of preparing movies is easy and achievable and thus encourages all branch teachers to use this technology in their lessons.     

Low temperature molten salt synthesis of YAG: Ce spherical powder and its thermally stable luminescent properties after post-annealing treatment

Spherical YAG: Ce particles were successfully synthesized at 350 °C by the molten-salt method. The effect of temperature and amount of salt on the crystallization and particle size of YAG: Ce were investigated thoroughly. The results demonstrated that the powders prepared at 350 °C in salt to reactant ratio 2:1 were pure YAG: Ce phase with 200–300 nm in particle size. The as-synthesized phosphors were later post annealed at 1200 °C in O₂, air and N₂, respectively. The results showed that the emission intensity of YAG: Ce sensitively depended on the post-treated atmosphere and the phosphor annealed in N₂ showed the highest emission intensities and a good thermal stability.     

Confined space reduced graphite oxide doped with sulfur as metal-free oxygen reduction catalyst

Reduced GO in confined space of silica gel nanopores doped with sulfur shows high catalytic activity for oxygen reduction reaction (ORR) in alkaline medium and exhibits a superior tolerance to the presence of methanol. Even though the partially reduced GO with hydroquinone structures is a good catalysts for ORR, it shows instability in KOH. The good performance of S-doped material is linked to the coexistence of sulfur and oxygen on the surface in equal atomic quantities and a unique porosity being the replica of the silica pores. The former leads to the positive charge on the carbon atoms, which are the reaction sites. Hydrophobicity of the surface and small pores enhance adsorption of O₂.     

Enhancement of the electroluminescence of organic light emitting devices based on Ir(ppy)3 by doping with metallic and magnetic nanoparticles

Magnetic nanoparticles embedded in the active layer of the Organic Light Emitting Diodes (OLEDs) significantly increases the electroluminescence and the charge transport without influencing the transparency of these devices. A brief comparison was done in order to identify which parameter influences these properties, by comparing the CoFe₂O₄ magnetic nanoparticles with CoFe₂ metallic magnetic nanoparticles, the latter one being obtained by thermal reduction in hydrogen of cobalt ferrite nanoparticles. CoFe₂ have shown a better efficiency of the metallic nanoparticles where probably the main advantage is the higher magnetization property instead of the coercive field. Concerning the charge transport across the OLEDs, these nanoparticles reduce the electron injection, acting as filling traps, which directly increases the electroluminescence and the current at the same voltage.