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Title: Development & Optimization of Materials and Processes for a Cost Effective Photoelectrochemical Hydrogen Production System. Final report

Abstract

The overall project objective was to apply high throughput experimentation and combinatorial methods together with novel syntheses to discover and optimize efficient, practical, and economically sustainable materials for photoelectrochemical production of bulk hydrogen from water. Automated electrochemical synthesis and photoelectrochemical screening systems were designed and constructed and used to study a variety of new photoelectrocatalytic materials. We evaluated photocatalytic performance in the dark and under illumination with or without applied bias in a high-throughput manner and did detailed evaluation on many materials. Significant attention was given to -Fe2O3 based semiconductor materials and thin films with different dopants were synthesized by co-electrodeposition techniques. Approximately 30 dopants including Al, Zn, Cu, Ni, Co, Cr, Mo, Ti, Pt, etc. were investigated. Hematite thin films doped with Al, Ti, Pt, Cr, and Mo exhibited significant improvements in efficiency for photoelectrochemical water splitting compared with undoped hematite. In several cases we collaborated with theorists who used density functional theory to help explain performance trends and suggest new materials. The best materials were investigated in detail by X-ray diffraction (XRD), scanning electron microscopy (SEM), ultraviolet-visual spectroscopy (UV-Vis), X-ray photoelectron spectroscopy (XPS). The photoelectrocatalytic performance of the thin films was evaluated and their incident photon

Authors:
Publication Date:
Research Org.:
University of California, Santa Barbara
Sponsoring Org.:
USDOE Office of Hydrogen, Fuel Cells, and Infrastructure Technologies Program (EE-2H)
OSTI Identifier:
1001994
Report Number(s):
DOE/FG36-05GO15040-100
TRN: US201106%%856
DOE Contract Number:
FG36-05GO15040
Resource Type:
Technical Report
Country of Publication:
United States
Language:
English
Subject:
08 HYDROGEN; EFFICIENCY; EVALUATION; FUNCTIONALS; HEMATITE; HYDROGEN; HYDROGEN PRODUCTION; ILLUMINANCE; OPTIMIZATION; PERFORMANCE; PHOTONS; PRODUCTION; SCANNING ELECTRON MICROSCOPY; SEMICONDUCTOR MATERIALS; SPECTROSCOPY; SYNTHESIS; THIN FILMS; WATER; X-RAY DIFFRACTION; X-RAY PHOTOELECTRON SPECTROSCOPY; Photocatalysis, solar-to-chemical, solar fuels, high-throughput screening

Citation Formats

McFarland, Eric W. Development & Optimization of Materials and Processes for a Cost Effective Photoelectrochemical Hydrogen Production System. Final report. United States: N. p., 2011. Web. doi:10.2172/1001994.
McFarland, Eric W. Development & Optimization of Materials and Processes for a Cost Effective Photoelectrochemical Hydrogen Production System. Final report. United States. doi:10.2172/1001994.
McFarland, Eric W. Mon . "Development & Optimization of Materials and Processes for a Cost Effective Photoelectrochemical Hydrogen Production System. Final report". United States. doi:10.2172/1001994. https://www.osti.gov/servlets/purl/1001994.
@article{osti_1001994,
title = {Development & Optimization of Materials and Processes for a Cost Effective Photoelectrochemical Hydrogen Production System. Final report},
author = {McFarland, Eric W},
abstractNote = {The overall project objective was to apply high throughput experimentation and combinatorial methods together with novel syntheses to discover and optimize efficient, practical, and economically sustainable materials for photoelectrochemical production of bulk hydrogen from water. Automated electrochemical synthesis and photoelectrochemical screening systems were designed and constructed and used to study a variety of new photoelectrocatalytic materials. We evaluated photocatalytic performance in the dark and under illumination with or without applied bias in a high-throughput manner and did detailed evaluation on many materials. Significant attention was given to -Fe2O3 based semiconductor materials and thin films with different dopants were synthesized by co-electrodeposition techniques. Approximately 30 dopants including Al, Zn, Cu, Ni, Co, Cr, Mo, Ti, Pt, etc. were investigated. Hematite thin films doped with Al, Ti, Pt, Cr, and Mo exhibited significant improvements in efficiency for photoelectrochemical water splitting compared with undoped hematite. In several cases we collaborated with theorists who used density functional theory to help explain performance trends and suggest new materials. The best materials were investigated in detail by X-ray diffraction (XRD), scanning electron microscopy (SEM), ultraviolet-visual spectroscopy (UV-Vis), X-ray photoelectron spectroscopy (XPS). The photoelectrocatalytic performance of the thin films was evaluated and their incident photon},
doi = {10.2172/1001994},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Mon Jan 17 00:00:00 EST 2011},
month = {Mon Jan 17 00:00:00 EST 2011}
}

Technical Report:

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  • The objective of this project is to develop critical technologies required for cost-effective production of hydrogen from sunlight and water using a-Si triple junction solar cell based photo-electrodes. In this project, Midwest Optoelectronics, LLC (MWOE) and its collaborating organizations utilize triple junction a-Si thin film solar cells as the core element to fabricate photoelectrochemical (PEC) cells. Triple junction a-Si/a-SiGe/a-SiGe solar cell is an ideal material for making cost-effective PEC system which uses sun light to split water and generate hydrogen. It has the following key features: 1) It has an open circuit voltage (Voc ) of ~ 2.3V and hasmore » an operating voltage around 1.6V. This is ideal for water splitting. There is no need to add a bias voltage or to inter-connect more than one solar cell. 2) It is made by depositing a-Si/a-SiGe/aSi-Ge thin films on a conducting stainless steel substrate which can serve as an electrode. When we immerse the triple junction solar cells in an electrolyte and illuminate it under sunlight, the voltage is large enough to split the water, generating oxygen at the Si solar cell side (for SS/n-i-p/sunlight structure) and hydrogen at the back, which is stainless steel side. There is no need to use a counter electrode or to make any wire connection. 3) It is being produced in large rolls of 3ft wide and up to 5000 ft long stainless steel web in a 25MW roll-to-roll production machine. Therefore it can be produced at a very low cost. After several years of research with many different kinds of material, we have developed promising transparent, conducting and corrosion resistant (TCCR) coating material; we carried out extensive research on oxygen and hydrogen generation catalysts, developed methods to make PEC electrode from production-grade a-Si solar cells; we have designed and tested various PEC module cases and carried out extensive outdoor testing; we were able to obtain a solar to hydrogen conversion efficiency (STH) about 5.7% and a running time about 480 hrs, which are very promising results; we have also completed a techno-economic analysis of our PEC system, which indicates that a projected hydrogen generation cost of $2/gge is achievable with a 50 Ton-per-day (TPD) scale under certain conditions.« less
  • This assessment was prepared to determine what impacts would result from (further) materials research for thermochemical hydrogen production. In this context, materials are those materials of construction that would be used for plant equipment such as heat exchangers, reactors, and the like. Process chemicals and catalysts are not within the scope of this study.
  • Properties of copper pastes did not reproduce earlier results in rheology and metallurgy. Electrodes made with pastes produced under the previous contract were analyzed and raw material characteristics were compared. A needle-like structure was observed on the earlier electroded solar cells, and was identified as eutectic copper-silicon. Experiments were conducted with variations in paste parameters, firing conditions, including gas ambients, furnace furniture, silicon surface and others to improve performance characteristics. Improved adhesion with copper pastes containing silver fluoride, as well as those containing fluorocarbon powder was obtained. Front contact experiments were done with silver fluoride activated pastes on bare silicon,more » silicon oxide and silicon nitride coated silicon wafers. Adhesion of pastes with AgF on silicon nitride coated wafers was good, but indications were that all cells were shunted and the conclusion was that these systems were unsuitable for front contacts. Experiments with aluminum back surfaces and screened contacts to that surface were begun. Low temperature firing tended to result in S shaped IV curves. This was attributed to a barrier formed at the silicon-copper interface. A cooperative experiment was initiated on the effect of heat-treatments in various atmospheres on the hydrogen profile of silicon surfaces. Contact theory was explored to determine the role of various parameters on tunneling and contact resistance. Data confirm that the presence of eutectic Al-Si additions are beneficial for low contact resistance and fill factors in back contacts. Copper pastes with different silver fluoride additions were utilized as front contacts at two temperatures. Data shows various degrees of shunting. Finally, an experiment was run with carbon monoxide gas used as the reducing ambient during firing.« less
  • H{sub 2}Gen, with the support of the Department of Energy, successfully designed, built and field-tested two steam methane reformers with 578 kg/day capacity, which has now become a standard commercial product serving customers in the specialty metals and PV manufacturing businesses. We demonstrated that this reformer/PSA system, when combined with compression, storage and dispensing (CSD) equipment could produce hydrogen that is already cost-competitive with gasoline per mile driven in a conventional (non-hybrid) vehicle. We further showed that mass producing this 578 kg/day system in quantities of just 100 units would reduce hydrogen cost per mile approximately 13% below the cost of untaxed gasoline per mile used in a hybrid electric vehicle. If mass produced in quantities of 500 units, hydrogen cost per mile in a FCEV would be 20% below the cost of untaxed gasoline in an HEV in the 2015-2020 time period using EIA fuel cost projections for natural gas and untaxed gasoline, and 45% below the cost of untaxed gasoline in a conventional car. This 20% to 45% reduction in fuel cost per mile would accrue even though hydrogen from this 578 kg/day system would cost approximatelymore » $4.14/kg, well above the DOE hydrogen cost targets of $2.50/kg by 2010 and $$2.00/kg by 2015. We also estimated the cost of a larger, 1,500 kg/day SMR/PSA fueling system based on engineering cost scaling factors derived from the two H{sub 2}Gen products, a commercial 115 kg/day system and the 578 kg/day system developed under this DOE contract. This proposed system could support 200 to 250 cars per day, similar to a medium gasoline station. We estimate that the cost per mile from this larger 1,500 kg/day hydrogen fueling system would be 26% to 40% below the cost per mile of untaxed gasoline in an HEV and ICV respectively, even without any mass production cost reductions. In quantities of 500 units, we are projecting per mile cost reductions between 45% (vs. HEVs) and 62% (vs ICVs), with hydrogen costing approximately $$2.87/kg, still above the DOE's 2010 $2.50/kg target. We also began laboratory testing of reforming ethanol, which we showed is currently the least expensive approach to making renewable hydrogen. Extended testing of neat ethanol in micro-reactors was successful, and we also were able to reform E-85 acquired from a local fueling station for 2,700 hours, although some modifications were required to handle the 15% gasoline present in E-85. We began initial tests of a catalyst-coated wall reformer tube that showed some promise in reducing the propensity to coke with E-85. These coated-wall tests ran for 350 hours. Additional resources would be required to commercialize an ethanol reformer operating on E-85, but there is no market for such a product at this time, so this ethanol reformer project was moth-balled pending future government or industry support. The two main objectives of this project were: (1) to design, build and test a steam methane reformer and pressure swing adsorption system that, if scaled up and mass produced, could potentially meet the DOE 2015 cost and efficiency targets for on-site distributed hydrogen generation, and (2) to demonstrate the efficacy of a low-cost renewable hydrogen generation system based on reforming ethanol to hydrogen at the fueling station.« less