Sign up for our newsletter!
Your data will be handled in compliance with our privacy policy.
Your data will be handled in compliance with our privacy policy.
With our carbon nanofibers (CNFs) fabrication technology, we develop advanced materials engineering solutions for use in water electrolysis and fuel cells for the hydrogen industry.
Fredrik Liljeberg • December 22, 2022
The demand for susÂtainÂably proÂduced hydroÂgen is risÂing due to its role in avoidÂing greenÂhouse gas emisÂsions. ProÂducÂtion and use of susÂtainÂable hydroÂgen is made posÂsiÂble by two core techÂnoloÂgies: Water elecÂtrolÂyÂsis, which proÂduces hydroÂgen from water using elecÂtricÂiÂty, and fuel cells, which reversÂes the reacÂtion to genÂerÂate elecÂtricÂiÂty. HowÂevÂer, both techÂnoloÂgies use rare and expenÂsive catÂaÂlyst mateÂriÂals such as platÂinum or iridÂiÂum. Using carÂbon nanofibers (CNF) as a catÂaÂlyst supÂport can decrease the amount of expenÂsive catÂaÂlyst mateÂrÂiÂal needÂed. Smoltek nanosÂtrucÂture fabÂriÂcaÂtion techÂnolÂoÂgy can unlock this potential.
HydroÂgen proÂduced by water elecÂtrolÂyÂsis can be a soluÂtion to sevÂerÂal probÂlems in the process of reducÂing greenÂhouse gas emisÂsions. For examÂple, interÂmitÂtent enerÂgy sources such as solar and wind powÂer occaÂsionÂalÂly proÂduce more elecÂtricÂiÂty than needÂed, e.g. on very windy or sunÂny days.
Using this elecÂtriÂcal powÂer for water elecÂtrolÂyÂsis allows the enerÂgy to be stored in the form of proÂduced hydroÂgen gas, which can latÂer be used conÂvertÂed back to elecÂtricÂiÂty by a fuel cell formÂing only water vapor in the process. AnothÂer key driÂver is to abate the carÂbon dioxÂide emisÂsion in the proÂducÂtion of steel, where coal and coke can be replaced by hydroÂgen gas as reducÂing agent for the iron ore emitÂting only water vapor and makÂing a sigÂnifÂiÂcant reducÂtion in globÂal carÂbon dioxÂide emisÂsions posÂsiÂble. This enables a fosÂsil-free steel production.
Water elecÂtrolyzÂers use two elecÂtrodes, a posÂiÂtiveÂly charged anode and a negÂaÂtiveÂly charged cathÂode, sepÂaÂratÂed by an elecÂtrolyte that allows ions to travÂel between the elecÂtrodes. The elecÂtrodes are also elecÂtriÂcalÂly conÂnectÂed to a powÂer source that supÂplies elecÂtriÂcal powÂer to driÂve the reacÂtion. OxyÂgen gas is proÂduced at the anode through the oxyÂgen evoÂluÂtion reacÂtion, and hydroÂgen gas is proÂduced at the cathÂode through the hydroÂgen evoÂluÂtion reacÂtion. CatÂaÂlysts are used to proÂmote these elecÂtroÂchemÂiÂcal reacÂtions and allow them to run at a lowÂer enerÂgy cost. The reacÂtions hapÂpen at the active catÂaÂlyst surÂface, i.e. at surÂfaces where the catÂaÂlyst is in conÂtact with the electrolyte.
BenÂeÂfiÂcial conÂdiÂtions for water elecÂtrolÂyÂsis depend on the type of elecÂtrolyte, the operÂatÂing temÂperÂaÂture, the presÂsure and the types of catÂaÂlysts. HisÂtorÂiÂcalÂly the indusÂtry has mostÂly relied on low-temÂperÂaÂture elecÂtrolyzÂers using an alkaÂline soluÂtion with high pH conÂtainÂing potasÂsiÂum hydroxÂide in water. They do not require scarce catÂaÂlyst mateÂrÂiÂal but cause limÂitÂed curÂrent denÂsiÂties and thereÂfore limÂitÂed hydroÂgen outÂput per cell area. This drawÂback can be overÂcome by polyÂmer ionomer memÂbranes that conÂduct either hydroÂgen ions or hydroxÂide ions in direct conÂtact with anode and cathÂode, so-called zero-gap design. These ion-conÂductÂing polyÂmers are known as proÂton exchange memÂbranes (PEM) or anion exchange memÂbranes (AEM) respectively.
Low-temÂperÂaÂture elecÂtrolyzÂers with PEM elecÂtrolytes, known as PEM elecÂtrolyzÂers, are promisÂing not only for their highÂer curÂrent denÂsiÂty but also for their excelÂlent match with interÂmitÂtent powÂer sources and the longeviÂty of the comÂmerÂcialÂly offered proÂton exchange memÂbranes. This enables a comÂpact and durable elecÂtrolyzÂer design.
For high-curÂrent denÂsiÂty operÂaÂtion at low overÂpoÂtenÂtial1 PEM elecÂtrolyzÂers need rare and expenÂsive of catÂaÂlysts such as platÂinum on the cathÂode side and iridÂiÂum oxide on the anode side. To realÂize the potenÂtial of PEM elecÂtrolyzÂers, it is cruÂcial that the catÂaÂlysts are used effiÂcientÂly and that the catÂaÂlyst load, i.e. the amount of catÂaÂlyst per unit area of the elecÂtrolyzÂer cell, is kept to a minimum.
One way of reducÂing the catÂaÂlyst load is to deposit the catÂaÂlyst mateÂrÂiÂal on anothÂer mateÂrÂiÂal known as a catÂaÂlyst supÂport, either in the form of a thin film or as parÂtiÂcles with a diamÂeÂter of a few nanomeÂters. The catÂaÂlyst supÂports act as a scafÂfoldÂing, allowÂing the catÂaÂlyst to be spread over a largÂer area. An ideÂal catÂaÂlyst supÂport should have a large surÂface area, an open strucÂture that lets water and gasÂes flow to and from the catÂaÂlyst, excelÂlent conÂtact with the proÂton exchange memÂbrane and good and staÂble elecÂtriÂcal conÂducÂtivÂiÂty to enable the elecÂtroÂchemÂiÂcal reacÂtions. CarÂbon black is often used as a catÂaÂlyst supÂport on the cathÂode side in PEM elecÂtrolyzÂers, but the iridÂiÂum catÂaÂlyst on the anode side is genÂerÂalÂly used withÂout supÂport due to the harsh acidic conÂdiÂtions at the anode.
CarÂbon nanofibers (CNF) are carÂbon strucÂtures with a diamÂeÂter that is typÂiÂcalÂly below 100 nm and a length between 1 and 100 µm. Like many carÂbon nanoÂmaÂteÂriÂals, CNF are elecÂtriÂcalÂly conÂducÂtive and mechanÂiÂcalÂly strong.
CNF are grown by chemÂiÂcal vapor depoÂsiÂtion (CVD) and have the potenÂtial to improve on existÂing catÂaÂlyst supÂports. The CVD growth method makes it posÂsiÂble to conÂtrol the oriÂenÂtaÂtion of the CNF so that they are verÂtiÂcalÂly aligned with a well-defined averÂage spacÂing, width, and height. This means that the strucÂture of a CNF catÂaÂlyst supÂport can be adjustÂed to achieve the large surÂface area and degree of porosÂiÂty that is needed.
The strucÂture of a CNF catÂaÂlyst supÂport also makes it posÂsiÂble to conÂtrol the posiÂtion of the catÂaÂlyst that is depositÂed on it, which in turn opens posÂsiÂbilÂiÂties for optiÂmizÂing the active surÂface area of the catÂaÂlyst and reducÂing the catÂaÂlyst load. For examÂple, the catÂaÂlyst can be placed in direct conÂtact or even embedÂded into the memÂbrane. The CNF can be conÂforÂmalÂly coatÂed and proÂtectÂed for use on the anode side of the electrolyzer.
Although reducÂing catÂaÂlyst load is most imporÂtant in PEM elecÂtrolyzÂers, CNF catÂaÂlyst supÂports may also be used in AEM elecÂtrolyzÂers and in PEM fuel cells. There are clear advanÂtages to using CNF grown by CVD as a catÂaÂlyst supÂport, such as increasÂing the active catÂaÂlyst surÂface area and decreasÂing the needÂed catÂaÂlyst load. The CVD methÂods used for CNF proÂducÂtion by Smoltek can be used to realÂize the potenÂtial of CNF in elecÂtrolÂyÂsis and fuel cells.
For future needs of the PEM elecÂtrolyzÂer marÂket, when the capacÂiÂty is scaled to proÂduce Gigawatts of water elecÂtrolÂyÂsis yearÂly it will be cruÂcial to manÂage a low iridÂiÂum catÂaÂlyst load on PEM anodes to enable cost-effiÂcient hydroÂgen production.
Smoltek’s nanofiber-based cell mateÂriÂals creÂates an optiÂmal anode strucÂture that allows iridÂiÂum catÂaÂlyst nanoparÂtiÂcles to form a highÂly active and accesÂsiÂble surÂface. In prinÂciÂple, all of the nanoparÂtiÂcles come into conÂtact with the proÂton exchange memÂbrane of the cell potenÂtialÂly reducÂing the needÂed amount of iridÂiÂum by 80% – or more.
AnothÂer benÂeÂfit is that the cells can be optiÂmized for high curÂrent denÂsiÂty, thus the capacÂiÂty to proÂduce hydroÂgen per cell area increasÂes. This is achieved by a corÂreÂspondÂing increase of the iridÂiÂum load. These design choicÂes can creÂate a 2–3 times lowÂer investÂment cost for the elecÂtrolyzÂer in a hydroÂgen plant.
Our next step is to indusÂtriÂalÂize our soluÂtion for the elecÂtrolyzÂer cell mateÂrÂiÂal (CNF-ECM). We are thereÂfore lookÂing for indusÂtriÂal partner(s) that, in close colÂlabÂoÂraÂtion with us;
Is your comÂpaÂny a potenÂtial partÂner in takÂing advanÂtage of our disÂrupÂtive techÂnolÂoÂgy?
ConÂtact us today, and let’s arrange a meetÂing to disÂcuss it further.
Your data will be handled in compliance with our privacy policy.