- 4개월 전
카테고리
📚
학습트랜스크립트
00:03Hello everyone, my name is Minho Lee, who is currently working as a Research Professor
00:09in Inter-University Research Institute for Energy Technology at Korea University.
00:16I am very honored to be here and thanks for an opportunity to introduce basic knowledge
00:21of hydrogen and my research work at Korea University and previous institutes that will
00:29be introduced in the slides later. Today, I am going to talk about electrochemical
00:35hydrogen production, especially powered by photovoltax, that is one of the representative
00:41renewable energies. This topic is now getting more attention because of the issues on achieving
00:48carbon neutrality. Okay, let's get started.
00:57This slide shows guiding framework of world energy transitions on loop theory of changing.
01:04All the countries discussed the global warming issues and decided to keep the temperature
01:10increase below 1.5 Celsius degree by 2100. Therefore, world pursues the path that is
01:20most likely to drive down energy emissions in the coming decades, and support emerging technologies,
01:28limit investments in oil and gas, and pays out coal and fossil fuel subsidies,
01:36reserve carbon capture and storage, adapt market structure for the new era energy, and so on.
01:52As you may know, currently, we face a serious problem regarding global warming and the energy crisis.
02:00They have a strong connection. Many scientists or experts have been trying to figure out
02:07what are the origins of the global warming and how temperature has been gradually increasing.
02:15They finally found that the concentration of the CO2 is strongly correlated to the temperature increase on the Earth.
02:24As you can see in the figure at the upper left side, both atmospheric CO2 and emission of the CO2
02:35are increasing as time passes,
02:39especially as CO2 emissions concentrations are sharply increasing after the industrial revolution around 1870.
02:52The figure at the bottom left side represents global warming predictions compared to the 1960 to 1990.
03:03The temperature is expected to increase high at least above 2 Celsius degree.
03:09That will lead to climate changes like many natural disasters such as flooding, drought, earthquake, hurricane, tornadoes, typhons, tsunamis.
03:27Additionally, the energy crisis is a critical issue in the energy supply.
03:35Oil is expected to be depleted in 2050.
03:42Natural gas in 2070 and coal is expected around 150 years later.
03:53Therefore, we need to prepare for the severe energy crisis that will happen in the near future.
04:01And we need to change the current dominant energy supply sources to cleaner and Earth-abundant
04:09and unlimited ones such as using sunlight, wind, and hydrogen.
04:25Here, I have an open question for you.
04:28Does anyone know the difference between carbon neutrality and net zero?
04:38This term sounds similar but a little bit different.
04:43The definition of net zero is the amount of greenhouse gases such as carbon dioxide, methane,
04:52or sulfur dioxide that are removed from the atmosphere is equal to those emitted by human activity.
05:02But the definition of carbon neutrality is more focused on carbon dioxide rather than other greenhouse gases.
05:11The world sets out a plan to reduce the amount of CO2 emissions by around 37 gigatons by 2050
05:24to keep temperature increase below 1.5 Celsius degree through six technological avenues.
05:41And another 25 percent is for increasing energy efficiency.
05:49And 20 percent is for electrification.
05:54Hydrogen is expected to be 10 percent of the sum.
06:04Hydrogen is the first element of periodic table as its atomic number is one,
06:14which means it has only one electron in its atom.
06:27Hydrogen is the most abundant chemical structure in the universe.
06:33The first industrial water electrolyte was developed in 1888.
06:41The meaning of hydrogen,
06:43hydrogen, the hydro means water,
06:46gen means crater.
06:48It's combustion release only water.
06:58Here you can see a couple of hydrogen properties.
07:02Density and pace of hydrogen, the solid, liquid, gas can be changed at different temperatures.
07:13The figures below shows flammability limit for hydrogen in air.
07:20It is safe below 4 percent or over 70 percent in the mixture of hydrogen in air.
07:29But if hydrogen ratio is between 4 percent and 75 percent,
07:35that will be highly dangerous due to the explosion.
07:39So we need to closely care about this matter.
07:47The specific energy of hydrogen, that is the stored energy by weight,
07:55is around 142 kg per gram, the highest of any practical fuel.
08:06LH means requifed hydrogen and CH2 means compressed hydrogen.
08:15Lithium-ion batteries and supercapacitors are positioned here
08:21and stored hydrogen and tanks positioned here.
08:28The values of specific energy are significantly reduced when stored in the tanks.
08:36This indicates storing technology of hydrogen would be highly important
08:42for the use of hydrogen as a fuel.
08:46So we need to develop the promising technology to store hydrogen efficiently.
08:59Hydrogen would be an ideal choice for the chemical storage of energy.
09:04As I mentioned earlier, hydrogen has the highest specific energy among the currently available
09:11pures.
09:12Besides the highest specific energy, hydrogen is regarded as an excellent energy carrier
09:19and hydrogen energy is environmentally benign because hydrogen can be used in a pure cell.
09:28Where hydrogen and oxygen meet, thereby generating electricity without any carbon emissions.
09:36And hydrogen is as safe as gasoline.
09:41Also hydrogen can be produced by a solar energy.
09:46Take a look at the right side.
09:49A schematic image of a personalized PV electrolyzer energy system is shown.
09:53In the right side.
09:55Integrating solar cells and electrolyzer energy system can provide affordable storage methods.
10:03For example, in daytime, electricity directly can be used in household appliance and electrical cars.
10:13And also can be used in water electrolyzer, which can split into oxygen and hydrogen.
10:22This hydrogen can be stored and used by the pure cells, which of electricity can be used in the nighttime.
10:39Hydrogen is an excellent energy carrier that can be used in many different applications.
10:46However, its actual use is still very limited.
10:51Each year, around 100 million tons of hydrogen are produced globally.
10:58Of which, two cells are pure hydrogen.
11:03And one cells are in a mixture with other gases.
11:09Take a look at the right figure.
11:12Hydrogen can be produced by a renewable energy.
11:16Integrated electrolyzer, which is one of the options for hydrogen production.
11:22This is just an example of a clean production.
11:28This hydrogen can be directly transported by shipping and trucks and pipeline.
11:36Also, hydrogen can be converted by a CO2 hydrogenation
11:43as stored in synthetic fuels.
11:47As well as converted to ammonia by a nitrogen hydrogenation.
11:53These fuels can be transported compared to compressed hydrogen or liquefied hydrogen.
12:02These liquid fuels are more cost-effective and safer.
12:08Therefore, many research activities are currently being studied.
12:12Hydrogen output is mostly used for crude oil, refining, and for ammonia and methanol synthesis,
12:24which together represent almost 75% of the combined fuel and mixed hydrogen demand.
12:33And hydrogen can be used for steel industry and transport, such as shipping,
12:43aviation, cars, rail, trucks, buses, and also for heating and power generation.
13:01Now, hydrogen has colors depending on production methods.
13:06Generally, this can be divided into three types, gray, blue, and green hydrogen.
13:18Today's hydrogen production is mostly based on fossil fuels, such as natural gas,
13:24contrast steam, methane, and steam methane repoling, and coal gasification.
13:29This method is to call gray hydrogen.
13:30We call this method gray hydrogen, which accounts for 95% of production.
13:39The use of gray hydrogen entails substantial CO2 emissions, which makes these hydrogen technologies unsuitable for the route toward net
13:53-zero emissions.
13:54During the early stage of the energy transition, the use of blue hydrogen, that means gray hydrogen with carbon capture
14:06and storage, could facilitate the growth of hydrogen market.
14:14Repurposing with carbon capture storage would allow the continued use of existing assets while still achieving lower greenhouse gas emissions.
14:28This is an option is to produce hydrogen with lower greenhouse gas emissions while reducing pressure on the renewable energy
14:39capacity installation rate to produce green hydrogen.
14:43Notably, industrial processes like steel production may require a continuous flow of hydrogen.
14:53Blue hydrogen could be an initial solution, while green hydrogen ramps up production and storage capacity to meet the continuous
15:03flow requirement.
15:06Lastly, green hydrogen, meaning hydrogen produced from renewable energy, is the most suitable one for the fully sustainable energy transition.
15:19The most established technology option for producing green hydrogen is water electricity powered by renewable electricity.
15:29Green hydrogen production through electricity is consistent with the net-zero route and allows the exploitation of synergies from sector
15:43coupling, thus decreasing technology cost and providing flexibility to the power system.
15:51For these reasons, green hydrogen from water electricity has been gaining increased interest.
16:04Depending on the kind of the electrolyte and the operation temperature, water electrolyzers are classified into three main categories, alkaline,
16:17PAM, and solid oxide electrolyzers.
16:21The operating principles of the three main types of electricity technologies are presented in the above figure.
16:32Alkaline and PAM electrolyzers operate at a low temperature range, typically below 100 Celsius degree, where water is liquid.
16:43Recent progress in the development of polymary membranes with proton conductivity operates at temperatures up to 200 Celsius degree, has
16:56been carried out in the field of pure cell technology, which can extend the temperature for PAM electrolyzers as well.
17:04In alkaline electrolyzers, the anode and cathode electrodes are immersed in a liquid alkaline electrolyte, most commonly potassium hydroxide.
17:19A diaphragm, a diaphragm, a permeable for hydroxide, between the two electrodes serves to separate the product gases.
17:29In PAM electrolyzers.
17:32In PAM electrolyzers and solid oxide electrolyzers, polymers and ceramics are used as the solid electrolytes respectively, fulfilling the role
17:42of the gas separator.
17:45Each of types of electrolyzers has its own pros and cons that are summarized in the below table.
17:54Alkaline electrolyzers is well established as the most applied commercial technology.
18:00Main advantages of alkaline electrolyzers are low cost, owing to the use of non-noble electrodes such as nickel and
18:12cobalt and long-term stability.
18:15On the contrary, the acidic environment in PAM electrolyzers hinders hinders the kinetics of the redox reactions and necessitates the
18:28use of expensive noble metal catalysis and materials for the bipolar plates.
18:37This, together with the high cost of polymeric membrane, is the main limitation for the commercialization of PAM electrolyzers in
18:48the near term.
18:51Solid oxide electrolyzers operate typically at temperatures over 500 Celsius degree with water in the form of steam.
19:00The solid oxide electrolyzer technology traditionally utilizes oxygen ion conductor, mainly etiostabilized zirconia.
19:14The efficiency of this type shows around 70%.
19:21Electrolyzer can be used with high temperature heat source like nuclear or geothermal power.
19:32The solid form of the electrolyte in the PAM and solid oxide electrolyzer enables a more compact design and operation
19:42at different pressure.
19:44It is feasible and favorable.
19:45Moreover, the solid nature of the electrolyte makes solid oxide electrolyzer and PAMs more dynamic systems with faster response upon
19:59application of a variable power load compared to liquid alkaline electrolyzers, where diffusion lights can be slow.
20:16In this slide, I am going to explain the basics and mechanism of water electrolyzers.
20:22When we applied enough power or voltage of 1.23 volt, water starts to split into oxygen and hydrogen gases.
20:35The total voltage of the electrolyte can be divided into four terms.
20:45The thermodynamic potential term is ideal voltage to split water.
20:55The change in Gibbs free energy is 277 kJ per mole, that is equal to 1.23 volt.
21:10The next term is a potential term of oxidation.
21:17Here, water can be oxidized to generate oxygen.
21:22Next is the potential term of reduction.
21:27Here, water can be reduced to generate hydrogen.
21:33The last term is a voltage drop term.
21:37Eons in the solution can be moved by diffusion from the concentration gradient.
21:45Therefore, considering the voltage drops in real conditions, around 1.6 to 1.8 volt is required to operate water
21:58splitting.
22:07Continually talk about the mechanism of water electrolyzers.
22:11The detailed reaction routes of hydrogen evolution reaction and oxygen evolution reaction are schematically shown in this figure.
22:23Notably, here, the way in acid is only shown for a better fundamental understanding.
22:30In the case of HL in an acid medium, the reduction of a proton takes place on the active site
22:40of the catalyst at the beginning step.
22:42This process is called as Burma step.
22:48Followed by hydrogen gas can be evolved by either the recombination of two absorbed protons placed close to each other.
23:02This is called tuppel step, or consecutive reduction of the proton.
23:09Together with electron transfer, this is called Helovski step.
23:18In contrast to the HL, a poor electron transfer process is required to generate 1 mole of oxygen gases in
23:31OER.
23:32Thus, OER is considered a bottleneck process in the whole water electrolysis system.
23:38Even though four different types of reaction mechanisms or OER have been suggested,
23:46here, the most recognized two mechanism electrochemical oxide and oxide pathways are only included in the below figure.
23:56As a first step, a water molecule is dissociated with the release of protons.
24:05Then, hydroxide is absorbed on the catalyst active site.
24:11Followed by oxygen bonds can be generated through either a successive proton release or oxidation along with the release of
24:31water molecules.
24:33Thereby, two absorbed oxygen atoms can result in the evolution of oxygen gases.
24:46Although water electrolysis is efficient and well studied in electrolytes with a high ionic concentration,
24:56hydrogen needs to be generated from the pure water for commercial viability and sustainability.
25:13This slide shows a phobic diagram for water including equilibrium regions for water and oxygen and hydrogens at standard temperature
25:25pressures.
25:25The vertical scales represent the electrode potential of hydrogen relative to a standard hydrogen electrode.
25:39The horizontal scale is the pH value of the electrolyte.
25:45Here, neglecting of potential, above the top line, the equilibrium condition is oxygen gas.
25:56Oxygen will bubble off the electrode until equilibrium is leached.
26:00Likewise, below the bottom line, the equilibrium condition is hydrogen gas.
26:10And hydrogen will bubble off of the electrode until equilibrium is leached.
26:21This slide shows thermodynamics for water electrolytes at atmospheric pressure.
26:28Here, actually, besides Gibbs free energy term, we need to consider heat term as well.
26:38Delta H represents the sum of the change in Gibbs free energy.
26:43That is equal to 237.1 kJ per mole electricity.
26:51And thermal term is multiplication of temperature and entropy changes.
27:01In this lecture, we exclude the thermal term.
27:05We assume all the reaction at room temperature or low temperature, meaning water is in liquid form.
27:20Sorry, please don't be confused.
27:23Here, we get back to the non-scientific part.
27:27I'm going to talk about the commercial status of the electroses.
27:31As you can see in the figure, currently alkaline electrolyzer dominates the market, and followed by PEM electrolyzer that is
27:45comparative to alkaline electrolysis,
27:49and lastly, high-temperature electrolysis that is less developed and small capacity was demonstrated.
27:58The size of circle indicates capacity of electrolysis installed.
28:12Based on the current project pipeline, global capacity has been gradually increasing and reached around 1,400 MW in 2022,
28:25almost tripling the 2021 level.
28:31Please note that white small circle indicates every size of new project, matched with light axis.
28:40Global electrolyzer capacity could stand at 134 GW in 2030.
28:51There are many uncertainties, of course, even for planned near-term project.
29:01Take a look at left side in the figure.
29:05Water electrolyzers can be fragmented in three levels, cell level, stack level, and system level.
29:14The cell is the core of the electrolyzers, and it is where the electrochemical process takes place.
29:22It is composed of two electrodes immersed in a liquid electrolyte, or close to a solid electrolyte membrane,
29:32two porous transport layers, and bipolar plates that provide mechanical support and distribute the flow.
29:44The stack has a protoscope, which includes multiple cells connected in series, spacers, seals, frames, and plates.
29:56The system level goes beyond the stack to include equipment for cooling and processing the hydrogen,
30:05e.g. for purity and compressions, converting the electricity input, treating the water supply, and gas output.
30:17For alkaline electrolyzers, the same reasoning in reducing the cost of the balance of plant components applied, such as power
30:29supply,
30:31and deionized water circulation, hydrogen processing, and cooling.
30:37As illustrated in the figure, within the stack, over 50% of the cost relate to the electrodes and diaphragm,
30:51as opposed to 25% of the cost in the PAM electrolyzer.
30:57Significant cost is associated with manufacturing of the electrodes,
31:02where learning by doing automatizations of the manufacturing process and economies of scale can play an important role in cost
31:15reduction.
31:21This slide shows how up to 85% of green hydrogen production costs can be reduced in the long term
31:28by a combination of cheaper electricity and electrolyzer capex investment in addition to increased efficiency and optimized operation of electrolyzer.
31:48A figure in this slide illustrates the potential green hydrogen production cost reduction between 2020 and 2050,
31:59for a range of electrolyzer costs and deployment levels.
32:04In the best case scenario, green hydrogen can already be produced at cost competitive with blue hydrogen today using low
32:16cost renewable electricity,
32:18around $20 per megawatt hour.
32:23A low electricity price is essential for the production of competitive green hydrogen.
32:29Cost reductions in the electrolyzer cannot compensate for high electricity prices.
32:39Combined with low electricity costs, an aggressive electrolyzer deployment pathway can make green hydrogen cheaper than any low carbon alternative
32:50before 2014.
32:53If rapid scale up takes place in the next decade,
32:58green hydrogen is expected to start becoming competitive with blue hydrogen by 2030 in a wide range of countries.
33:09Those with electricity price of $30 per megawatt hour.
33:20Here are an example of a PAM electricity for green hydrogen cost.
33:28Electricity has a high portion of over 50% of the total cost in the electricity.
33:34So, the most important thing is cost reduction of electricity in the electricity.
33:42Solar electricity can be an alternative of current method for electricity generations.
33:52Indeed, in Europe, the cost of electricity by solar cell is already lower than the other methods such as coal,
34:03wind, natural gas, and nuclear.
34:10So, in countries having low electricity cost, we can generate hydrogen by a solar cell more cheaply.
34:24Also, the problem for electricity is carbon emission.
34:29Figures summarize the results of carbon emissions depending on hydrogen production method.
34:34Overall, we find that electricity using 2030 global average grid electricity shows highest greenhouse gas emissions for 2030 of pathways
34:48analyzed here.
34:50In the case of water electricity, this is mostly due to the 16% coal power share in the global
34:59grid mix assumed.
35:00In contrast, if we directly connect solar cell with PAM electrolyzer, greenhouse gas emissions significantly reduced to 1.
35:13That is around 11 times reduction compared to the grid electricity base 1.
35:20Here, carbon taxes are not included in the total cost of hydrogen production.
35:26Currently, a lot of countries are adopting carbon taxes, so cost will be more expensive if grid electricity is used
35:35because carbon emission is high.
35:39Our country, South Korea, is currently not adopting carbon taxes, so more advantageous abroad, especially the country adopts carbon taxes.
35:50We cannot ignore whether carbon taxes are adopted or not for the concentration of the total hydrogen cost.
36:02As you know, solar cells have the inherent dropback that sunlight is intermittent due to the cycles of nature.
36:11So, renewable energy supply is irregular sometimes high enough at noon or summer, sometimes very low at night, rainy or
36:23winter.
36:25At sunlight available high enough, generally we cannot use this surplus renewable energy.
36:32So, as an alternative, this surplus energy can be converted and stored in the chemical form like hydrogen.
36:42And this stored energy can be used in the deficit conditions.
36:48Therefore, we can control and use the sunlight more efficiently.
36:58Likewise, renewable energy such as photovoltaic and wind turbines can be connected to the electrolyzers.
37:06In this case, generally the power output of the photovoltaic and electrolyzer is different.
37:12So, usually use the converter to match the appropriate output.
37:18In the case of photovoltaics, a DC-DC, a direct current-direct current converter is used for matching stubble voltage.
37:30The price of the converter is around 5 to 10% of total system.
37:37So, it would be necessary to remove this converter and therefore we need to consider and make a design without
37:45this DC-DC converter for reducing the cost of hydrogen.
37:53From now on, I am going to tell you the directory coupling of photovoltaics and electrolyzer.
38:00Before getting to the point, I am going to briefly explain to you on different types of solar water splitting.
38:07Generally, the solar water splitting research field can be classified into three categories.
38:13The first, a particulate photocatalyst.
38:17This particle is immersed in the water and they have a high enough voltage for driving this water splitting reaction
38:25when sunlight is illuminated.
38:27The second, the photoelectrochemical way, we briefly call PC device protist type.
38:37Each N-type and P-type semiconductor is separated from the membrane.
38:44The N-type semiconductor means the concentration of electron is rich in the semiconductor.
38:56When light illuminates in this system, photovoltaics is generated at each semiconductor and oxygen is evolved at the N-type
39:07side and hydrogen is evolved at the P-type side.
39:12And lastly, the photovoltaic electrolyzer devices.
39:19Here, photovoltaic is directly connected to electrolyzer.
39:24Photovoltaic needs to have enough voltage to drive water splitting.
39:29While the particulate system cannot separate products like oxygen and hydrogen.
39:38But PC and PVC system is able to separate products because the membrane can be established in the electrolyzer.
39:57This slide shows the relationship between the efficiency with the system complexity.
40:03Although the preparation of PVC system is more complicated than the other particulate and PC system,
40:20PVC system holds high levels of solar to hydrogen efficiency.
40:27Also, both PV and electrolyzer systems are already well-natured.
40:34Additionally, the cost of each part of the PV and electrolyzer has been continuously decreasing,
40:42making a PVC system more competitive in the supply of eco-friendly and sustainable hydrogen.
40:50Most of these parts in this field say PVC systems will be dominated the market in the near future.
40:59Therefore, I'm going to talk about the photovoltaic electrochemical devices more detailed in this presentation.
41:12As thermodynamic potential of water splitting is 1.23V,
41:17most single-junction solar cells like silicon and copper-indium-gallium selenide solar cells are not enough to provide voltage
41:27for splitting water.
41:30High voltage can be generated using multi-junction solar cells connected in series vertically.
41:40Vertically integrated multi-junction structure gives some of the open circuit voltage of the both subcells.
41:49We can also consider module with lateral side-by-side series connection.
41:57Their voltage will be determined by multiplying number of single cells.
42:04With this structure, we can provide enough voltage for spontaneous water splitting.
42:18Here, a bit more complex equation is represented.
42:22Don't worry about that.
42:23Very simple if you understand the system.
42:27A block diagram of directly coupled PV and EC for water splitting
42:32and corresponding steady-state equivalent circuit of an integrated PV system are shown in figure A and B.
42:44The diagram of the PV system is coupled through direct electrical connections.
42:53The power flows are graphically indicated in the graph.
43:00Current density voltage curves of PV are shown in blue line and EC with red line are shown.
43:14The intersection point of each JV curve is considered the operation current of the PVC.
43:23system.
43:26VOC means open circuit voltage.
43:30JS means short circuit current density.
43:35JOP means operating current density.
43:38VOC means operating voltage.
43:42This indicates thermodynamic reaction potential.
43:49In the integrated PVC arrangement, the total solar-pure efficiency.
43:59Its solar-to-pure convergent efficiency comprise the three efficiency terms.
44:07That is, the efficiency of the photovoltaics, the efficiency of the electrolyzer system, and coupling efficiency between PV and EC.
44:19Each representing parameter is graphically explained in PSC.
44:28Therefore, the solar-pure efficiency can be simplified by combining the above three peak efficiency expressions.
44:43That means, we already know the thermodynamic potential, that is 1.23 volt for water splitting, and illumination intensity.
44:58Therefore, just we measure the operation current over integrated devices, and then we can calculate the solar-hydrogen efficiency.
45:15From now on, I'm gonna give you several demonstrations of photovoltaic-driven water-splitting devices.
45:23Actually, these works I did at ULLI Research Center, which is a government-funded institute located in Germany.
45:32As a power source, among different types of solar cells, we have used the thin film-silicon solar cell in
45:42this study.
45:43Because thin film-silicon solar cell technology has already matured, and these solar cells are relatively durable and cost-effective.
45:57Importantly, it can be produced in a multi-junction structure.
46:02Its photovoltaic can be modulated in a wide range from 1.5 volt up to 2.8 volt, enabling it
46:14to provide enough voltage to overcome thermodynamic water-splitting potential of 1.23 volt,
46:21without need for the lateral series connection of single subcells.
46:32We extended our concept to large-scale devices.
46:36PV module was designed with laser scribing.
46:39The water-splitting catalysts were placed side by side on the back side of the PV module.
46:48The insulating epoxy was used as a corrosion protection layer against alkaline electrolyte, as well as electrical insulation.
47:02A membrane was used for separating gas products, where an ion or carion can transport them.
47:13Extending to a large area by the partition of the base unit, we were able to develop the epicent of
47:22bias-free and wireless PVC devices,
47:25with solar-2 hydrogen efficiency of up to 4.7%.
47:32Moreover, both oxygen and hydrogen gas separation was enabled by introducing an ion-exchange membrane in the 3D-printed device
47:45body,
47:46which inhibits undesired back-reaction and risk of gas explosion.
47:56The figure A shows a schematic and optical image of the PVC device type 3.
48:04And figure B shows cross-sectional schematic image of an integrated PVC device.
48:12Have a look at PGCE.
48:14The crystalline silicon solar cell was connected with the electrolyzer,
48:21and above 13% of solar-2 hydrogen efficiency was achieved.
48:32Additionally, in this work, we have developed a cobalt-ion-banadium oxide catalyst for water-splitting.
48:39Just I wanted to let you know briefly the principle of how we predict the optimal catalysts that make designed
48:48efficiently.
48:49On the basis of the 7-tier principle that the interaction energy between the substrate and catalyst should have a
49:00balanced value that should be neither too strong for dissociation of the target product,
49:06nor too weak for binding the substrate nor too weak for binding the substrate to the active site of the
49:12catalyst.
49:13I prepared a series of cobalt-based or mixed catalyst based on the metal-itox side bond strength.
49:21Here, two samples near the optimization value are selectively represented in the purple dotted over.
49:38We were able to get a result of bi-functional cobalt-ion-banadium oxide catalyst that is shown in this
49:45slide.
49:46As we predicted in the previous slide, the sample having optimized binding energy has shown the best performance for water
49:56-splitting.
49:59The potential means the extra energy from the ideal value is required to derive reactions. Therefore, lower O-potential indicates
50:10higher performance.
50:15From now on, I want to introduce a project named PEXIS, Technology Demonstration of Large Scale Photo-Electrochemical Systems for
50:26Solar Hydrogen Production.
50:27The duration of the project was four years, starting in January 2017 and ended December 2020.
50:39Funding budget was 2.5 million euros funded by European Union.
50:46The PEXIS consortium consists of a multidisciplinary mix of three public research institutes, one university, and two manufacturers of commercial
51:01PV modules.
51:06The PEXIS project was aimed at demonstrating a 10 square meter solar-driven electrochemical hydrogen generation system.
51:17Our particular focus was to highlight concept with the levelized cost of hydrogen production below 5 euro per kilogram
51:28and to achieve hydrogen production of 16 gram hydrogen per hour and thus solar to hydrogen conversion efficiency of at
51:39least 6%
51:41with less than 10% decrease in performance after 6 months of continuous operation.
51:53The schematic that summarizes the results of the different PVEC approaches investigated within the PEXIS project is shown in this
52:04slide.
52:05TRL means technology readiness level.
52:11That is low for an innovative concept with the highest degree of integration like the one shown in the left
52:21figure.
52:23An intermediate level was the concept.
52:26Adapted PV was both electrically and thermally integrated EC.
52:37Here thermal integration has an advantage for the EC part.
52:43For example, when sunlight illuminates the temperature of the portable tax is increasing
52:50and thermally effects on the electrolyte part that reduce the activation energy to split water.
52:59Lastly, potability was connected only electrically without thermal connections.
53:08Just commercial photovoltaic and electrolyte were connected electrically.
53:13That shows highest TRL with the highest technical maturity and lifetime.
53:22And highest solar to hydrogen efficiency was achieved with this concept.
53:32This slide shows the project results and is directly compared with other research projects previously conducted in the world.
53:43The detailed performance of the larger systems operated under real sun conditions in comparison with similar size systems developed in
53:53the past 10 years and reported in other studies is shown in this slide.
54:00The demonstrations in this project showed relatively high solar to hydrogen efficiency, especially our final demonstrations at large scale device
54:13above 10 square meter.
54:16Our demonstration was able to achieve the world record with exceeding 10% solar to hydrogen efficiency.
54:33This slide represents our final demonstration and the detailed information about photovoltaic array, the area and power and stability and
54:51efficiency.
54:52And production light.
55:02Compared to the previous demonstrations, our system shows our performing results.
55:11Up to now, this demonstration holds world record efficiency in the field of directly integrated photovoltaic electrolyzer system.
55:20In particular, the demonstrator was operated for a long time period, a total of nine months than other systems for
55:33which typically directly PV to EC coupling is only
55:37studied on a short-term basis.
55:49Yeah, it would be better to see a thing one time than hear about it 100 times.
56:00Please take a look at this video for your demonstration.
56:16Please take a look at this video for your demonstration.
56:29See you then.
56:29Bye-bye.
56:32Check it out.
56:34Bye-bye.
56:44Do you see that we use añade green light light?
57:17다음 영상에서 만나요.
57:45다음 영상에서 만나요.
58:17다음 영상에서 만나요.
58:22감사합니다.