{"id":58149,"date":"2018-11-09T07:35:38","date_gmt":"2018-11-09T06:35:38","guid":{"rendered":"https:\/\/renewable-carbon.eu\/news\/?p=58149"},"modified":"2021-09-09T21:32:45","modified_gmt":"2021-09-09T19:32:45","slug":"hybrid-photoelectrochemical-and-photovoltaic-cells-for-simultaneous-production-of-chemical-fuels-and-electrical-power","status":"publish","type":"post","link":"https:\/\/renewable-carbon.eu\/news\/hybrid-photoelectrochemical-and-photovoltaic-cells-for-simultaneous-production-of-chemical-fuels-and-electrical-power\/","title":{"rendered":"Hybrid photoelectrochemical and photovoltaic cells for simultaneous production of chemical fuels and electrical power"},"content":{"rendered":"

In the quest for abundant, renewable alternatives to fossil fuels, scientists have sought to harvest the sun\u2019s energy through \u201cwater splitting,\u201d an artificial photosynthesis technique that uses sunlight to generate hydrogen fuel from water. But water-splitting devices have yet to live up to their potential because there still isn\u2019t a design for materials with the right mix of optical, electronic, and chemical properties needed for them to work efficiently.<\/strong><\/p>\n

Now researchers at the U.S. Department of Energy\u2019s Lawrence Berkeley National Laboratory (Berkeley Lab) and the Joint Center for Artificial Photosynthesis (JCAP), a DOE Energy Innovation Hub, have come up with a new recipe for renewable fuels that could bypass the limitations in current materials: an artificial photosynthesis device called a \u201chybrid photoelectrochemical and voltaic (HPEV) cell\u201d that turns sunlight and water into not just one, but two types of energy \u2013 hydrogen fuel and electricity. The paper describing this work <\/a>was published on Oct. 29 in Nature Materials.<\/em><\/p>\n

\"Device-schematic-3D-1522-628x525\"<\/a>
The HPEV cell\u2019s extra back outlet would allow the current to be split into two, so that one part of the current contributes to solar fuels generation, and the rest can be extracted as electrical power. (Credit: Berkeley Lab, JCAP)<\/figcaption><\/figure>\n

 <\/p>\n

Finding a way out for electrons<\/h3>\n

Most water-splitting devices are made of a stack of light-absorbing materials. Depending on its makeup, each layer absorbs different parts or \u201cwavelengths\u201d of the solar spectrum, ranging from less-energetic wavelengths of infrared light to more-energetic wavelengths of visible or ultraviolet light.<\/p>\n

When each layer absorbs light it builds an electrical voltage. These individual voltages combine into one voltage large enough to split water into oxygen and hydrogen fuel. But according to Gideon Segev, a postdoctoral researcher at JCAP in Berkeley Lab\u2019s Chemical Sciences Division and the study\u2019s lead author, the problem with this configuration is that even though silicon solar cells can generate electricity very close to their limit, their high-performance potential is compromised when they are part of a water-splitting device.<\/p>\n

The current passing through the device is limited by other materials in the stack that don\u2019t perform as well as silicon, and as a result, the system produces much less current than it could \u2013 and the less current it generates, the less solar fuel it can produce.<\/p>\n

\u201cIt\u2019s like always running a car in first gear,\u201d said Segev. \u201cThis is energy that you could harvest, but because silicon isn\u2019t acting at its maximum power point, most of the excited electrons in the silicon have nowhere to go, so they lose their energy before they are utilized to do useful work.\u201d<\/p>\n

Getting out of first gear<\/h3>\n
\"XBD201702-00026-62.tif\"
Lead author Gideon Segev and co-author Jeffrey W. Beeman are both JCAP researchers in Berkeley Lab\u2019s Chemical Sciences Division. (Credit, left-right: Marilyn Chung\/Berkeley Lab, Jeffrey W. Beeman\/Berkeley Lab).<\/figcaption><\/figure>\n

So Segev and his co-authors \u2013 Jeffrey W. Beeman, a JCAP researcher in Berkeley Lab\u2019s Chemical Sciences Division, and former\u00a0Berkeley Lab and JCAP researchers Jeffery Greenblatt, who now heads the Bay Area-based technology consultancy Emerging Futures LLC, and Ian Sharp, now a professor of experimental semiconductor physics at the Technical University of Munich in Germany \u2013 proposed a surprisingly simple solution to a complex problem.<\/p>\n

\u201cWe thought, \u2018What if we just let the electrons out?\u2019\u201d said Segev.<\/p>\n

In water-splitting devices, the front surface is usually dedicated to solar fuels production, and the back surface serves as an electrical outlet. To work around the conventional system\u2019s limitations, they added an additional electrical contact to the silicon component\u2019s back surface, resulting in an HPEV device with two contacts in the back instead of just one. The extra back outlet would allow the current to be split into two, so that one part of the current contributes to solar fuels generation, and the rest can be extracted as electrical power.<\/p>\n

When what you see is what you get<\/h3>\n
\"HPEV-calc\"
(Credit: Berkeley Lab, JCAP)<\/figcaption><\/figure>\n

After running a simulation to predict whether the HPEC would function as designed, they made a prototype to test their theory. \u201cAnd to our surprise, it worked!\u201d Segev said. \u201cIn science, you\u2019re never really sure if everything\u2019s going to work even if your computer simulations say they will. But that\u2019s also what makes it fun. It was great to see our experiments validate our simulations\u2019 predictions.\u201d<\/p>\n

According to their calculations, a conventional solar hydrogen generator based on a combination of silicon and bismuth vanadate, a material that is widely studied for solar water splitting, would generate hydrogen at a solar to hydrogen efficiency of 6.8 percent. In other words, out of all of the incident solar energy striking the surface of a cell, 6.8 percent will be stored in the form of hydrogen fuel, and all the rest is lost.<\/p>\n

In contrast, the HPEV cells harvest leftover electrons that do not contribute to fuel generation. These residual electrons are instead used to generate electrical power, resulting in a dramatic increase in the overall solar energy conversion efficiency, said Segev. For example, according to the same calculations, the same 6.8 percent of the solar energy can be stored as hydrogen fuel in an HPEV cell made of bismuth vanadate and silicon, and another 13.4 percent of the solar energy can be converted to electricity (see figure, left). This enables a combined efficiency of 20.2 percent, three times better than conventional solar hydrogen cells.<\/p>\n

The researchers plan to continue their collaboration so they can look into using the HPEV concept for other applications such as reducing carbon dioxide emissions. \u201cThis was truly a group effort where people with a lot of experience were able to contribute,\u201d added Segev. \u201cAfter a year and a half of working together on a pretty tedious process, it was great to see our experiments finally come together.\u201d<\/p>\n

The Joint Center for Artificial Photosynthesis is a DOE Energy Innovation Hub.<\/p>\n

The work was supported by the DOE Office of Science.<\/p>\n

 <\/p>\n

About Lawrence Berkeley National Laboratory<\/h3>\n

Lawrence Berkeley National Laboratory addresses the world\u2019s most urgent scientific challenges by advancing sustainable energy, protecting human health, creating new materials, and revealing the origin and fate of the universe. Founded in 1931, Berkeley Lab\u2019s scientific expertise has been recognized with 13 Nobel Prizes. The University of California manages Berkeley Lab for the U.S. Department of Energy\u2019s Office of Science.<\/p>\n

About DOE\u2019s Office of Science<\/h3>\n

DOE\u2019s Office of Science is the single largest supporter of basic research in the physical sciences in the United States, and is working to address some of the most pressing challenges of our time. For more information, please visit the Office of Science website at science.energy.gov.<\/p>\n","protected":false},"excerpt":{"rendered":"

In the quest for abundant, renewable alternatives to fossil fuels, scientists have sought to harvest the sun\u2019s energy through \u201cwater splitting,\u201d an artificial photosynthesis technique that uses sunlight to generate hydrogen fuel from water. But water-splitting devices have yet to live up to their potential because there still isn\u2019t a design for materials with the […]<\/p>\n","protected":false},"author":59,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"_seopress_robots_primary_cat":"","nova_meta_subtitle":"","footnotes":""},"categories":[5572,5571],"tags":[5627,10630],"supplier":[7487,11236,4116],"class_list":["post-58149","post","type-post","status-publish","format-standard","hentry","category-bio-based","category-co2-based","tag-energy","tag-hydrogen","supplier-jcap","supplier-u-s-department-of-energy","supplier-us-doe-office-of-science-sc"],"_links":{"self":[{"href":"https:\/\/renewable-carbon.eu\/news\/wp-json\/wp\/v2\/posts\/58149","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/renewable-carbon.eu\/news\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/renewable-carbon.eu\/news\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/renewable-carbon.eu\/news\/wp-json\/wp\/v2\/users\/59"}],"replies":[{"embeddable":true,"href":"https:\/\/renewable-carbon.eu\/news\/wp-json\/wp\/v2\/comments?post=58149"}],"version-history":[{"count":0,"href":"https:\/\/renewable-carbon.eu\/news\/wp-json\/wp\/v2\/posts\/58149\/revisions"}],"wp:attachment":[{"href":"https:\/\/renewable-carbon.eu\/news\/wp-json\/wp\/v2\/media?parent=58149"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/renewable-carbon.eu\/news\/wp-json\/wp\/v2\/categories?post=58149"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/renewable-carbon.eu\/news\/wp-json\/wp\/v2\/tags?post=58149"},{"taxonomy":"supplier","embeddable":true,"href":"https:\/\/renewable-carbon.eu\/news\/wp-json\/wp\/v2\/supplier?post=58149"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}