03 AUG 2023: In a recent study, a collaborative group of researchers consisting of City University (CityU), The University of Hong Kong (HKU), Jiangsu University, and the Shanghai Institute of Organic Chemistry under the Chinese Academy of Sciences has successfully created a reliable artificial photocatalytic system that surpasses the efficiency of natural photosynthesis. This advanced system mimics a natural chloroplast and effectively converts carbon dioxide in water into methane – a valuable fuel – using light. This achievement marks a substantial advancement with the potential to play a pivotal role in attaining carbon neutrality.
The research team adopted a supramolecular assembly method to construct a synthetic photosynthetic system that emulates the arrangement found in light-absorbing chromatophores of purple bacteria. These cells, rich in pigment, excel in harnessing solar energy transfer.
At the core of the novel artificial photosynthesis setup lies a remarkably stable synthetic nanomicelle. This specialised polymer possesses the ability to arrange itself in aqueous environments, featuring both water-attracting (hydrophilic) and water-repelling (hydrophobic) segments. The hydrophilic section serves as a light-absorbing photosensitizer, capturing sunlight, while the hydrophobic tail triggers the self-assembly process.
When immersed in water, the nanomicelles come together spontaneously, facilitated by hydrogen bonding between water molecules and the tails. Introducing a cobalt catalyst leads to the creation of hydrogen through photocatalysis and the reduction of carbon dioxide, yielding hydrogen and methane as end products.
By utilising sophisticated imaging techniques and rapid spectroscopy, the researchers revealed the atomic attributes of the novel photosensitizer. They found that the distinct configuration of the hydrophilic head in the nanomicelle, combined with the hydrogen bonding between water molecules and the nanomicelle's tail, results in a dependable, water-friendly synthetic photosensitizer. This addresses the long-standing issues of instability and incompatibility with water in artificial photosynthesis. Additionally, the interaction between the photosensitizer and cobalt catalyst, coupled with the efficient light-absorbing antenna capability of the nanomicelle, enhanced the overall photocatalytic process.
Researchers found that the rate of methane generation throughout the experiment exceeded 13,000 μmol h−1 g−1, exhibiting a quantum yield of 5.6% during a 24-hour period. Additionally, an impressive solar-to-fuel efficiency rate of 15% was attained, surpassing the capabilities of natural photosynthesis.
In the City University’s official press release, Professor Ye Ruquan, Associate Professor in the Department of Chemistry at CityU, expressed confidence that this recent breakthrough will have positive implications, serving as a guide for designing future photocatalytic systems aimed at converting and reducing carbon dioxide using solar energy. This advancement contributes to the overarching objective of achieving carbon neutrality.
Katika utafiti wa hivi karibuni, kikundi cha watafiti wa ushirikiano wa Chuo Kikuu cha Jiji (CityU), Chuo Kikuu cha Hong Kong (HKU), Chuo Kikuu cha Jiangsu, na Taasisi ya Kimakemia ya Kikaboni ya Shanghai chini ya Chuo Kikuu cha Sayansi cha China imefanikiwa kuunda mfumo wa photocatalysis ya bandia ambayo inazidi ufanisi wa photosynthesis ya asili. Mfumo huo wa hali ya juu huiga kloroplasti ya asili na kwa ufanisi hubadilisha kaboni dioksidi katika maji kuwa metani - mafuta yenye thamani - kwa kutumia nuru. Mafanikio haya yanaashiria maendeleo makubwa na uwezo wa kucheza jukumu muhimu katika kufikia kutokuwepo kwa kaboni. Timu ya utafiti ilitumia mbinu ya mkusanyiko wa supramolecular kujenga mfumo wa photosynthetic ya synthetic ambayo huiga mpangilio uliopatikana katika chromatophores ya kuingiza mwanga ya bakteria ya zambarau. Chembe hizo, zenye rangi nyingi, zina uwezo mkubwa wa kutumia nishati ya jua. Katika kiini cha mfumo mpya wa fotosynthesis bandia liko nanomicelle ya synthetic thabiti sana. Polymer hii maalumu ina uwezo wa kupanga yenyewe katika mazingira ya maji, akishirikiana na sehemu zote mbili za kuvutia maji (hydrophilic) na kuondoa maji (hydrophobic). Sehemu ya hydrophilic hutumika kama photosensitizer ya kunyonya mwanga, kukamata mwanga wa jua, wakati mkia wa hydrophobic huchochea mchakato wa kujikusanya. Wanapozama ndani ya maji, nanomicelles huungana kwa njia ya moja kwa moja, ikisaidiwa na vifungo vya hidrojeni kati ya molekuli za maji na mikia. Kuingiza kichocheo cha cobalt husababisha uundaji wa hidrojeni kupitia photocatalysis na kupunguzwa kwa kaboni dioksidi, ikitoa hidrojeni na methane kama bidhaa za mwisho. Kwa kutumia mbinu za hali ya juu za upigaji picha na spectroscopy ya haraka, watafiti walifunua sifa za atomu za photosensitizer mpya. Utaratibu wa kichwa cha hydrophilic katika nanomicelle, pamoja na uhusiano wa hidrojeni kati ya molekuli za maji na mkia wa nanomicelle, huongoza kwenye photosensitizer ya kisanii ya kuaminika na ya kibinadamu. Hii inashughulikia masuala ya muda mrefu ya kutokuwa na utulivu na kutoelewana na maji katika photosynthesis bandia. Kwa kuongezea, mwingiliano kati ya photosensitizer na kichocheo cha cobalt, pamoja na uwezo mzuri wa antenna ya kunyonya mwanga wa nanomicelle, iliboresha mchakato wa jumla wa photocatalytic. Kwa mfano, katika jaribio la kwanza, kiwango cha methane kilikuwa zaidi ya 13,000 μmol h-1 g-1 na kilikuwa na uwezo wa kutokeza methane kwa muda wa saa 24. Kwa kuongezea, kiwango cha ufanisi wa nishati ya jua ya 15% ilifikiwa, ikizidi uwezo wa photosynthesis ya asili. Katika taarifa rasmi ya City University, Profesa Ye Ruchun, Profesa Mshirika katika Idara ya Kemia katika City University, alielezea imani kwamba mafanikio haya ya hivi karibuni yatakuwa na athari nzuri, kutumika kama mwongozo kwa kubuni mifumo ya baadaye ya photocatalysis inayolenga kubadilisha na kupunguza kaboni dioksidi kwa kutumia nishati ya jua. Maendeleo haya yanachangia lengo kuu la kufikia kutokuwepo kwa kaboni.