Solar Cell for Hydrogen Preparation
Development of Cascade Solar Cell with Heterojunctions on the Basis of Metal Oxides and their Solid Solutions as Breakthrough in the Problem of Hydrogen Preparation from Water
Tech Area / Field
- NNE-SOL/Solar Energy/Non-Nuclear Energy
- CHE-RAD/Photo and Radiation Chemistry/Chemistry
- PHY-SSP/Solid State Physics/Physics
3 Approved without Funding
Belorussian State Technological University, Belarus, Minsk
- National Academy of Sciences of the Republic of Belarus / Institute of General and Inorganic Chemistry, Belarus, Minsk
- University of Dublin / Trinity College Dublin, Ireland, Dublin\nUniversità degli Studi di Firenze, Italy, Florence
Project summaryThe purpose of the project. The creation of a cascade solar cell with p-n, n-n, p-p heterojunctions intended for photodecomposing of water on hydrogen and oxygen and consisting only of metal oxides and their solid solutions with n- and p- conductivity and with band gap (1 - 3.5) eV, that will allow essentially advance the solution of hydrogenous power engineering problem by obtaining the basic power supply - hydrogen from marine and sweet water.
Recent state in the field of explorations.Since 70th years of the 20th century in various scientific centres of the world many works have been carried out devoted to the water photodecomposition on film structures and fine-grained powders of TiO2, WO3, SrTiO3, CdS, GaP contacting with Pt, RuO2 nano-particles catalyzing processes of hydrogen and oxygen evolution (M. Schiavello (Ed) Heterogeneous photocalalysis, Wiley Chichester, 1997; M. Gratzel, Photoelectrochemical cells, Nature, Vol. 414, 2001, P. 338-344). Major hopes were set on this direction of scientific researches in a solution of a problem of hydrogen preparation from water by means of sunlight energy with the purpose of solvins a problem of hydrogen energetics. Unfortunately, these hopes were not justified yet that was stipulated mainly by small value of efficiency of such nano-sized systems and existing photoelectrochemical cells at water photocatalytic decomposition, because in sunlight there are not enough ultraviolet generating pairs “electron – hole” in high energy-gap (Eg ~ 3 eV) oxides TiO2, SrTiO3 as well as owing to slight spatial separation of photoelectrons and holes. In essence the system of nano-particles Pt – TiO2 (SrTiO3) – RuO2 represents the solar cell which at photocatalytic decomposition of water fulfills the same role as an external current source at water elecrolysis but owing to the above reasons its efficiency is only 4 – 5 %. This problem is not solved by means of creation of tandem photoelectrochemical cells based on two high energy-gap oxides (WO3, TiO2, etc) and a dye as a photosensitizer. Now in the USA and in the Western Europe researches are intensively conducting on improvement of solar cells on the basis of new achievements in physics and chemistry of semiconductors. It has allowed to increase efficiency of thin film cells up to ~ 20 % and cascade photoconverters – up to efficiency ~ 30 % as well as to lower cost of energy production by these devices to 0.13 USD /(kW:h). In opinion of the Project participants such high value of efficiency may be reached also at photocatalytic decomposition of water on hydrogen and oxygen. For this purpose it is necessary to create cascade photoelectrochemical cell based on high energy-gap and narrow band metal oxides with n- and p-type of conduction.
Current Project Influence on the Progress in the Field of the Science.Using successes achieved to the present time at a solution of problems of solar cells and photoelectrochemistry of semiconductors, in the Project it is proposed to develop new film cascade solar cells on the basis only of metal oxides. Creation of such cells will allow to increase essentially efficienсy of carrying out the process of photocatalytic decomposition of water on hydrogen and oxygen at sunlight action (efficienсy 30 %) and thereby to make a break in a deadlock scientific direction – preparation of hydrogen from sea and fresh water which in the future will be the basic ecologically pure energy carrier. Earlier in photoelectrochemical cells on the basis of highenergy-gap semiconductors narrow band semiconductors (Si, CuInSe2, GaP, GaAs et al) were used for more complete use of solar energy at water photodecomposition. However in an aqueous medium they are not stable and quickly destruct under electrolyte action. Participants of the Project instead of them propose to use narrow band (1.1 – 1.3 eV) metal oxides that will allow to increase considerably term of operation photoelectrochemical cell for water decomposition on hydrogen and oxygen. For reaching a water decomposition potential (2 – 2.5 V) two and more cascade cells will be series connected.
Project participants competence in the given area. This project is consistent with the traditional area of interests for ‘armament’ scientists which are involved in it, but is directed to civil technologies.
The Project Manager, Dr N.Y. Shishkin (BSTU), is a well-known scientist specialized in the field of physical chemistry of solid state, including oxide materials for gas sensor applications and photocatalysts; he has authored the textbook on solid state chemistry. The Assistant of Project Manager, Prof. A.I. Kulak (IGIC NASB), is a well-known expert in electrochemistry, photoelectrochemistry and photocatalytic properties of nanoheterostructures based on metal oxides and other semiconductors; he has a book on this topic. The Scientific Manager of the project Prof. L.A. Bashkirov is a well-known scientist in the field of metals oxides (and their compounds) physical chemistry (Project Manager of the fulfilled ISTC project #B-625). Prof. Bodnar I.V. – leading expert in the field of semiconductor compounds of metals halkogen’s and solar elements on their basis.
Expected Results.Category of development: applied investigations.
At fulfillment of the 3 problems of the project the following results for the first time will be:
- obtained and investigated the photoelectrochemical properties of new film cascade solar cells with one p-n and two - four n-n, p-p heterojunctions on the basis of metal oxides with different band gap (1,1 - 3,4) eV with n- and p- conductivity (problem 1).
- obtained and investigated photoelectrochemical properties of new film cascade solar cells with three р-n heterojunctions (three-element photoconverters) on the basis of the same metal oxides with n- p- conductivity as at the solution of the problem 1, but at the other order of their arrangement (problem 2).
- made the model solar cell on the basis of the designed cascade solar film cells and the capability of its usage for obtaining in quantities of gaseous hydrogen and oxygen studied at photocatalytic decomposing of water at solar radiation (problem 3).
Thus, for the first time will be obtained and investigated the oxides with given physical characteristicss (coplex and discordant) and their structural combinations in heterojunctions, which one should have extremely high performance of a radiation energy conversionin into chemical fuel. Solar cells thus will be built, the application which one in an industry will be commercially justified.
Expected Results and their Application. It is expected, that the usage of the designed new cascade film solar cells on the basis of metals oxides with n- and p- conductivity and with different band gap will allow largely to troubleshoot obtainings hydrogen from marine and sweet water for needs of non-polluting hydrogen power engineering, that will allow hereafter to avoid a world (global) energy crisis at an exhaustion of oil and gas on the Earth.
Meeting ISTC Goals and Objectives.This project corresponds to the objectives and tasks of ISTC because:
- the project promotes reorientation of the abilities of experts in areas of rocket and laser materials, materials for chemical weapons to civil researches by utilizing their experience in the development of new solar cells;
- the project encourages the integration of the project participants into international scientific community by their involvement in solving a problem of photoelectrochemical decomposition of water at action of sunlight;
- the project supports the basic and applied researches and development of non-military technologies especially in hydrogen preparation at water photodecomposition;
- the project supports transition of its participants to the market economy that matches the civil needs by supposed advance new developed solar cells to the market.
Scope of Activities. The project will last 30 months. The total labour expenses amount to 6275 man-days, including 4465 man-days for the Leading Institution (BSTU), 1810 man-day for the Participating Institution (IGIC NASB). Three tasks are to be fulfilled to achieve the goals of the project. The labour expenses for the first and the second tasks amount a 2510 man-days for each, while the labour expenses for the third task amount to 1255 man-days. The tasks ate carried out, one by another, simultaneously by all the participants of the project. The project participants from the Leading Institution (BSTU) are specialized in the synthesis and investigation of a film cascade solar cells with different width of bandgap on the basis of metals oxides and different type of conductivity. The project participants from the Participating Institution (IGIC NASB) are responsible for sol-gel synthesis of metals oxides films and photoelectrochemical and photoelectrochemical measurements. The coordination among two research groups in the Leading Institution (BSTU) and one research group in the Participating Institution (IGIC NASB) is performed by Dr N.Y. Shishkin. Scientific guidance of the entire project is performed by Prof. L.A. Bashkirov.
Role of Foreign Collaborators. The foreign collaborators Prof. Ugo Bardi (Dipartmento Di Chimica Universita di Firenze, Italy), Prof. Gun’ko (Department of Chemistry, Trinity College, Dublin, Ireland) will be involved in the following cooperation within the framework of the Project:
the information exchange dealing with the solution of actual problems of photoelectrochemical decomposition of water;
- representation of the comments on the technical reports of the Project participants to ISTC;
- participation in technical control of the activities due to the Project by the ISTC officials;
- organization of joint seminars to discuss the obtained results and preparation of joint publications;
- organization of independent expert examination of work of developed model solar cell consisting of two cascade elements for hydrogen and oxygen preparation at photoelectrochemical decomposition of water at sunlight illumination (Ugo Bardi);
- organization of independent expert examination of efficiency of hydrogen and oxygen preparation at sunlight illumination of developed cascade three- element photoelectrochemical converter (Y. Gunko);
- consultation on the protection of the intellectual property and joint patenting of the developed solar cascade cells;
- assistance in evaluation of the market requierements in the developed new solar cells.
The technical approaches and methodology. In the project for the first time for essential increase of photoelectrochemical cell overall performance permitting to conduct photocatalytic decomposing of water into hydrogen and oxygen at solar radiation, the technical approach and scientific methodology of creation of cascade solar cells on the basis of p - n heterojunction and last achievements in the field of photoelectrochemistry of heterostructures of semiconductors will be utilised.
For achievement of the purpose it is proposed for the first time to elaborate a film cascade solar cell with p-n, n-n, p-p heterojunctions, on exteriors of which one place films of wide band gap (Eg ~3.0-3,4 eV) metals oxides (n-TiO2, n-SrTiO3, p-Cr2O3) with n- and p- conductivity and with redox potentials permitting to conduct recovery and oxidation of water up to allocation of hydrogen and oxygen at their illumination by a sunlight from two parts. Behind them a film of metals oxides with bandgap width of (2,3 - 2,0) eV (n-Bi2O3, p-Ni(Co)Al2O4) is placed, pasted on a substrate of narrow-bandgap oxide of metal with width of (1,1-1,3) eV with n- or p- conductivity (n-Ti1-xSnxO2, p-Ni1-xCoxAl2O4, p-Cr2O3, doped accordingly by oxides of antimony and lithium). The participants of the project accumulate a wide experience of complex researches in the field of creation of oxide heterostructures with given physical characteristicss and comprehension of processes descending at irradiation by the light of a definite wave band, and also creation and research of thin-film solar cells. The technical and methodological approaches of photoelectrochemistry of semiconductors designed by the participants of the project will be utilised.
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