• Journal of Hydrogen and New Energy
• /
• v.22 no.2
• /
• pp.206-212
• /
• 2011

The effect of process parameters on $H_2$ production from water vapor excited by HF ICP has been qualitatively examined for the first time. With the increase of ICP power, characteristics of $H_2$ production from $H_2O$ dissociation in plasma was divided into 3 regions according to both reaction mechanism and energy efficiency. At the edge of region (II) in the range of middle ICP power, energy effective hydrogen production from $H_2O$ plasma can be achieved. Furthermore, within the region (II) power condition, heating of substrate up to $500^{\circ}C$ shows additional increase of 70~80% in $H_2$ production compared to $H_2O$ plasma without substrate heating. This study have shown that combination of optimal plasma power (region II) and wall heating (around $500^{\circ}C$) is one of effective ways for $H_2$ production from $H_2O$.

• Journal of the Korean Society of Visualization
• /
• v.20 no.3
• /
• pp.117-127
• /
• 2022

The present study has investigated the performance of hydrogen gas generators for inhalation purposes based on polyelectrolyte membrane water electrolysis (PEMWE). The system applied two watering methods. One is pumped water (pumping system) and the other is gravity-fed water without a pump (non-pumping system). The cell efficiencies were compared by measuring the cell voltage and temperature in the hydrogen gas generator, respectively. The results show that the cell voltage and temperature increase with the cell current. The cell temperature is lower in the pumping system than that in the non-pumping system at a given cell current. Even though the amount of hydrogen production is the same regardless of the pumping system, the cell efficiency of the hydrogen gas generator in the non-pumping system is better than that in the pumping system.

• Journal of Hydrogen and New Energy
• /
• v.33 no.5
• /
• pp.507-514
• /
• 2022

There is growing interest in sustainable energy sources that can reduce fossil fuel dependence and environmental pollution while meeting rapidly growing energy demands. Hydrogen have been investigated as one of the ideal alternative energies because it has relatively high efficiency without emitting pollutants. The light-sensitized enzymatic (LSE) system, which uses hydrogenase-enzymes, is one of the methods towards economically feasible system configurations that enhance the rate of hydrogen generation. Hydrogenase is an enzyme that catalyzes a reversible reaction that oxidizes molecular hydrogen or produces molecular hydrogen from protons and electrons. In this paper, utilization of [NiFe]-hydrogenase (from Pyrococcus furiosus) in photoelectrochemical hydrogen production system such as handling, immobilization, physicochemical and electrochemical analysis, process parameters, etc. was introduced.

• Journal of Hydrogen and New Energy
• /
• v.18 no.4
• /
• pp.458-463
• /
• 2007

An experimental study on scale-up of Electro-electrodialysis(EED) to increase the efficiency of HI decomposition section in the IS(Iodine-Sulfur) process was carried out. The EED stack extends the effective area of the membrane to 20 times of that formerly used in a single EED unit cell. The experiment was carried out using HIx solution($HI:H_2O:I_2=1:8.4{\sim}9:1.85{\sim}1.9$) at $100^{\circ}C$ and various solution flow rates of 20, 30, 40 and 50 cc/min. The increased HI molality in catholyte after one-pass throughout from the EED stack was 3 mol/kg-$H_2O$, 2.2 mol/kg-$H_2O$, 2 mol/kg-$H_2O$ and 1.37 mol/kg-$H_2O$ at 20, 30, 40 and 50 cc/min, respectively. These values satisfied the target of HI molality(the increase of HI molality: 2 mol/kg-$H_2O$) in the IS process for hydrogen production of 20 L/hr.

• Journal of Hydrogen and New Energy
• /
• v.34 no.2
• /
• pp.132-140
• /
• 2023

In this study, rotary magnet holder (RMH) was manufactured to analyze the ion transport effect according to the rotating magnetic field for the hydrogen production efficiency by alkaline water electrolyte. In the experiment, the voltage signal according to the magnet arrangement inside the RMH, the rotation speed, and the rotation time was measured using the voltage measurement module. As a result of the voltage signal measurement experiment, the average potential difference increased as the rotation speed of the RMH increased. Through the results of the voltage signal measurement experiment, the most efficient magnet arrangement (case 2) was applied to the RMH to conduct a water electrolysis experiment. A 20% NaOH aqueous solution was filled in the electrolytic cell, and a direct current 2 V constant voltage was applied to measure the current value according to the RMH rotation to compare the hydrogen generation amount. When rotating at 100 RPM, the hydrogen production efficiency increased by 8.06% compared to when not rotating. Considering the area exceeding +25 mA, which was not measured at the beginning of the experiment, an increase in hydrogen production of about 10% or more can be expected.

• KSBB Journal
• /
• v.20 no.6
• /
• pp.443-446
• /
• 2005

Hydrogen fermentation from food waste was attempted at different hydraulic retention time(HRT, 18-42 h). A continuous reactor fed with ground, alkali-treated and diluted food waste(average VS 4.4%) exhibited stable hydrogen production during 126 days. Hydrogen production depended on HRT, resulting in the maximum values of 25.8 mL $H_2/g\;VS_{added}$, 0.36 mol $H_2/mol\;hexose_{added}$ and 0.91 L $H_2/L/d$ at HRT 30 h. n-Butyrate and isopropanol production increased with hydrogen production increased, while acetate production decreased. The fermentation efficiency ranged from 53.3 to 65.7%, which implied that hydrogen fermentation would substitute conventional acidogenesis of food waste.

• Journal of Hydrogen and New Energy
• /
• v.27 no.4
• /
• pp.329-334
• /
• 2016

Hydrogen is eco-friendly alternative energy source and the photoelectrochemical water splitting is believed to be one of the promising methods for hydrogen production. Many researchers have studied several potential photocatalysts to increase the photoelectochemical performance efficiency for hydrogen conversion. In this study, the GO (graphene oxide) was prepared by Tour's method and was dispersed in precursor solutions of $WO_3$ and $BiVO_4$. Those precursor solutions were spin-coated on FTO glass and several photocatalyst thin films of $WO_3$, $BiVO_4$ and $WO_3/BiVO_4$ were prepared by calcination. The morphologies of prepared photocatalyst thin films were measured by scanning electron microscope. The photoelectrochemical performances of photocatalyst thin films with rGO (reduced graphene oxide) and without rGO were analyzed systematically.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2013.08a
• /
• pp.251.2-251.2
• /
• 2013

Natural photosynthesis utilizes two proteins, photosystem I and photosystem II, to efficiently oxidize water and reduce NADP+ to NADPH. Artificial photosynthesis which mimics this process achieve water splitting through a two-step Z-schematic water splitting process using man-made synthetic materials for hydrogen fuel production. In this study, Z-scheme system was achieved from the hybrid materials which composed of hydrogen production part as photosystem I protein and water oxidizing part as semiconductor BiVO4. Utilizing photosystem I as the hydrogen evolving part overcomes the problems of existing hydrogen evolving p-type semiconductors such as water instability, expensive cost, few available choices and poor red light (>600 nm) absorbance. Some problems of photosystem II, oxygen evolving part of natural photosynthesis, such as demanding isolation process and D1 photo-damage can also be solved by utilizing BiVO4 as the oxygen evolving part. Preceding research has not suggested any protein-inorganic-hybrid Z-scheme composed of both materials from natural photosynthesis and artificial photosynthesis. In this study, to realize this Z-schematic electron transfer, diffusion step of electron carrier, which usually degrades natural photosynthesis efficiency, was eliminated. Instead, BiVO4 and Pt-photosystem I were all linked together by the mediator gold. Synthesized all-solid-state hybrid materials show enhanced hydrogen evolution ability directly from water when illuminated with visible light.

• 한국신재생에너지학회:학술대회논문집
• /
• 2011.05a
• /
• pp.158.2-158.2
• /
• 2011

DME is acronym of dimethyl ether, which is spotlighted as an ideal fuel to produce hydrogen due to its high hydrogen/carbon ratio, high energy density and easiness to carry. In this research, we calculated thermodynamic hydrogen (or syngas) yield from DME autothermal reforming and compared to other fuels. The reforming efficiency was about 80% above $700^{\circ}C$. Lower OCR has higher reforming efficiency but, it requires additional heat supply since the reactions are endothermic. SCR has no significant effect on the reforming efficiency. The optimized condition is $700^{\circ}C$, SCR 1.5, OCR 0.45 without additional heat supply. Comparing to other commercial gaseous fuels (methane and propane), DME has higher selectivity of $H_2O$ and $CO_2$ than the others due to the oxygen atom in the molecule. To apply DME autothermal reforming to real system, a proper catalyst is required. Therefore, it is performed the experiment comparing various novel metal catalysts based on CGO. Experiments were performed at calculated condition. The composition of product was measured and reforming efficiency was calculated. The catalysts have similar efficiency at high temperature(${\sim}800^{\circ}C$) but, CGO-Ru has the highest efficiency at low temperature ($600^{\circ}C$).

• Nuclear Engineering and Technology
• /
• v.39 no.2
• /
• pp.111-122
• /
• 2007

The current energy supply system is burdened by environmental and supply problems. The concept of a hydrogen economy has been actively discussed worldwide. KAERI has set up a plan to demonstrate massive production of hydrogen using a VHTR by the early 2020s. The technological gap to meet this goal was identified during the past few years. The hydrogen production process, a process heat exchanger, the efficiency of an I/S thermochemical cycle, the manufacturing of components, the analysis tools of VHTR, and a coated particle fuel are key areas that require urgent development. Candidate NHDD plant designs based on a 200 MWth VHTR core and I/S thermochemical process have been studied and some of analysis results are presented in this paper.