Researchers from the University of Adelaide and Tianjin University have successfully split seawater without pre-treatment to produce green hydrogen. A paper on the work is published in Nature Energy.
The use of vast amounts of high-purity water for hydrogen production may aggravate the shortage of freshwater resources. Seawater is abundant but must be desalinated before use in typical proton exchange membrane (PEM) electrolysers. Here we report direct electrolysis of real seawater that has not been alkalised nor acidified, achieving long-term stability exceeding 100 h at 500 mA cm−2 and similar performance to a typical PEM electrolyser operating in high-purity water.
This is achieved by introducing a Lewis acid layer (for example, Cr2O3) on transition metal oxide catalysts to dynamically split water molecules and capture hydroxyl anions. Such in situ generated local alkalinity facilitates the kinetics of both electrode reactions and avoids chloride attack and precipitate formation on the electrodes.
A flow-type natural seawater electrolyser with Lewis acid-modified electrodes (Cr2O3–CoOx) exhibits the industrially required current density of 1.0 A cm−2 at 1.87 V and 60 °C.—Guo et al.
University of Adelaide’s Professor Shizhang Qiao, co-corresponding author, said that the researchers used a non-precious and cheap catalyst in a commercial electrolyzer.
Our work provides a solution to directly utilise seawater without pre-treatment systems and alkali addition, which shows similar performance as that of existing metal-based mature pure water electrolyser.—Yao Zheng, co-author
Seawater electrolysis is still in early development compared with pure water electrolysis because of electrode side reactions, and corrosion arising from the complexities of using seawater.
It is always necessary to treat impure water to a level of water purity for conventional electrolysers including desalination and deionisation, which increases the operation and maintenance cost of the processes. Our work provides a solution to directly utilise seawater without pre-treatment systems and alkali addition, which shows similar performance as that of existing metal-based mature pure water electrolyser.—Yao Zheng
The team will work on scaling up the system by using a larger electrolyzer so that it can be used in commercial processes such as hydrogen generation for fuel cells and ammonia synthesis.
Guo, J., Zheng, Y., Hu, Z. et al. (2023) “Direct seawater electrolysis by adjusting the local reaction environment of a catalyst.” Nat Energy doi: 10.1038/s41560-023-01195-x
Watafiti kutoka Chuo Kikuu cha Adelaide na Chuo Kikuu cha Tianjin wamefanikiwa kugawanya maji ya bahari bila matibabu ya awali ili kutengeneza hidrojeni ya kijani. Karatasi juu ya kazi hiyo imechapishwa katika Nishati ya Asili. Matumizi ya kiasi kikubwa cha maji safi sana kwa ajili ya uzalishaji wa hidrojeni yaweza kuzidisha upungufu wa rasilimali za maji baridi. Maji ya bahari ni mengi lakini lazima desalinated kabla ya matumizi katika kawaida proton kubadilishana utando (PEM) electrolysers. Katika kesi hii, electrolysis ya moja kwa moja ya maji ya bahari halisi ambayo haijawahi kuwa alkali au acidifying, kufikia utulivu wa muda mrefu zaidi ya 100h katika 500mA cm2 na utendaji sawa na electrolyser ya kawaida ya PEM inayofanya kazi katika maji safi. Hii hutimizwa kwa kuingiza safu ya asidi ya Lewis (kwa mfano, Cr2O3) kwenye kichocheo cha oksidi ya chuma cha mpito ili kugawanya molekuli za maji kwa nguvu na kukamata anions za hydroxyl. Kama in situ yanayotokana alkalinity ndani kuwezesha kinetics ya wote electrode athari na kuepuka chloride shambulio na precipitate malezi juu ya electrodes. Mtiririko aina ya asili maji ya bahari electrolyser na Lewis asidi-modified electrodes (Cr2O3 <COX) inaonyesha viwanda required sasa wiani wa 1.0 A cm2 katika 1.87 V na 60 ° C. Profesa Shijiazhuang Qiao wa Chuo Kikuu cha Adelaide, mwandishi mwenza, alisema kuwa watafiti walitumia kichocheo kisicho cha thamani na cha bei nafuu katika electrolyzer ya kibiashara. "Kazi yetu inatoa suluhisho la kutumia moja kwa moja maji ya bahari bila mifumo ya kabla ya matibabu na kuongeza alkali, ambayo inaonyesha utendaji sawa na ile ya sasa ya chuma-msingi wa maji safi electrolyser. ""Yao Zheng, mwandishi mwenza, ""Maji ya bahari electrolysis bado ni katika maendeleo ya mapema ikilinganishwa na maji safi electrolysis kwa sababu ya electrode upande athari, na kutu yanayotokana na utata wa kutumia maji ya bahari." Ni daima muhimu kutibu maji yasiyo safi kwa kiwango cha usafi wa maji kwa ajili ya electrolysers kawaida ikiwa ni pamoja na desalination na deionization, ambayo huongeza gharama ya uendeshaji na matengenezo ya taratibu. "Kazi yetu inatoa suluhisho la kutumia moja kwa moja maji ya bahari bila mifumo ya kabla ya matibabu na kuongeza alkali, ambayo inaonyesha utendaji sawa na ile ya sasa ya chuma-msingi wa maji safi ya mzee electrolyzer. ""Yao Zheng, Mtaalamu wa Utafiti wa Utafiti wa Utafiti wa Utafiti wa Utafiti wa Utafiti wa Utafiti wa Utafiti wa Utafiti wa Utafiti wa Utafiti wa Utafiti wa Utafiti wa Utafiti wa Utafiti wa Utafiti wa Utafiti wa Utafiti wa Utafiti wa Utafiti wa Utafiti wa Utafiti wa Utafiti wa Utafiti wa Utafiti wa Utafiti wa Utafiti wa Utafiti wa Utafiti wa Utafiti wa Utafiti wa Utafiti wa Utafiti wa Utafiti wa Utafiti wa Utafiti." Guo, J., Zheng, Y., Hu, Z. et al. "Kutumia ""Mchanganyiko wa umeme wa maji ya bahari"" ni njia ya kuunda mfumo wa umeme wa maji ya bahari kwa kutumia njia ya umeme wa maji ya bahari, ambayo inahitajika kwa ajili ya ufumbuzi wa maji ya bahari, na ambayo inaweza kutumika kwa ajili ya ufumbuzi wa maji ya bahari."