新系統模擬光合作用過程，特別是紫色細菌的有效能量轉移

太陽能轉化為燃料的效率為15%，這種方法超過自然光合作用，并以令人印象深刻的速度產生甲烷

創新和可持續的過程利用廉價的、地球上豐富的元素，潛在地推進碳中和的目標

據油價網2023年8月12日報道，香港城市大學的一個研究小組最近開發了一種穩定的人工光催化系統，比自然光合作用更有效。新系統模擬天然葉綠體，利用光線將水中的二氧化碳轉化為甲烷，后者是一種很有價值的燃料。這一有希望的發現可能有助于實現碳中和的目標。

光合作用是指植物和一些生物體內的葉綠體利用陽光、水和二氧化碳來產生食物或能量的過程。在過去的幾十年里，許多科學家試圖開發人工光合作用過程，將二氧化碳轉化為碳中和燃料。

香港城市大學化學系副教授葉如泉教授是這項聯合研究的負責人之一，他解釋說：“然而，由于許多光敏劑或催化劑在水中降解，因此很難在水中轉換二氧化碳。盡管人工光催化循環已被證明具有更高的內在效率，但在水中減少二氧化碳的低選擇性和穩定性阻礙了它們的實際應用。”

香港城市大學、香港大學、江蘇大學和中國科學院上海有機化學研究所的聯合研究小組在《自然催化》雜志上發表的最新研究中，克服了這些困難，利用超分子組裝方法創建了一個人工光合系統。它模仿了紫色細菌的捕光色素體(即含有色素的細胞)的結構，這種色素體在從太陽轉移能量方面非常有效。

新的人工光合系統的核心是一種高度穩定的人工納米膠束——一種可以在水中自組裝的聚合物，具有親水和疏水兩端。納米膠束的親水頭部作為光敏劑吸收陽光，其疏水尾部作為自組裝的誘導劑。

當它被放入水中時，由于水分子和納米膠束疏水尾部之間的分子間氫鍵，納米膠束會自組裝。添加鈷催化劑可產生光催化制氫和二氧化碳還原，從而產生氫氣和甲烷。

利用先進的成像技術和超快光譜學，該團隊揭示了創新光敏劑的原子特征。他們發現，納米膠束親水頭部的特殊結構，以及水分子與納米膠束疏水尾部之間的氫鍵，使其成為一種穩定的、與水相容的人工光敏劑，解決了人工光合作用的傳統不穩定性和水不相容問題。光敏劑與鈷催化劑之間的靜電相互作用以及納米膠團的強捕光天線效應改善了光催化過程。在實驗中，研究小組發現甲烷的產率超過13000微摩爾每克每小時，24小時的量子產率為5.6%。它還實現了高效的太陽能轉化為燃料的效率，達到15%，超過了自然光合作用。

最重要的是，新的人工光催化系統在經濟上是可行的和可持續的，因為這種新的人工光催化系統不依賴昂貴的貴金屬。葉如泉教授說：“系統的分層自組裝提供了一種有前途的自下而上的策略，可以創建一個精確控制的高性能人工光催化系統，這個系統基于廉價的、地球上豐富的元素，如鋅和鈷卟啉復合物。”

葉如泉教授還表示，他相信這一最新發現將有利于并啟發未來利用太陽能進行二氧化碳轉化和還原的光催化系統的合理設計，為實現碳中和的目標形成積極助力。

李峻 譯自 油價網

原文如下：

New Catalyst Paves Way For Green Methane Production

·     The new system mimics the photosynthesis process, specifically the efficient energy transfer in purple bacteria.

·     With a 15% solar-to-fuel efficiency rate, this method surpasses natural photosynthesis and produces methane at an impressive rate.

·     The innovative and sustainable process utilizes cheap, Earth-abundant elements, potentially advancing the goal of carbon neutrality.

A City University of Hong Kong research team recently developed a stable artificial photocatalytic system that is more efficient than natural photosynthesis. The new system mimics a natural chloroplast to convert carbon dioxide in water into methane, a valuable fuel, very efficiently using light. This promising discovery could contribute to the goal of carbon neutrality.

Photosynthesis is the process by which chloroplasts in plants and some organisms use sunlight, water and carbon dioxide to create food or energy. In past decades, many scientists have tried to develop artificial photosynthesis processes to turn carbon dioxide into carbon-neutral fuel.

Professor Ye Ruquan, Associate Professor in the Department of Chemistry at CityU, one of the leaders of the joint study explained, “However, it is difficult to convert carbon dioxide in water because many photosensitizers or catalysts degrade in water. Although artificial photocatalytic cycles have been shown to operate with higher intrinsic efficiency, the low selectivity and stability in water for carbon dioxide reduction have hampered their practical applications.”

In the latest study published in Nature Catalysis, the joint-research team from CityU, The University of Hong Kong (HKU), Jiangsu University and the Shanghai Institute of Organic Chemistry of the Chinese Academy of Sciences overcame these difficulties by using a supramolecular assembly approach to create an artificial photosynthetic system. It mimics the structure of a purple bacteria’s light-harvesting chromatophores (i.e. cells that contain pigment), which are very efficient at transferring energy from the sun.

The core of the new artificial photosynthetic system is a highly stable artificial nanomicelle – a kind of polymer that can self-assemble in water, with both a water-loving (hydrophilic) and a water-fearing (hydrophobic) ends. The nanomicelle’s hydrophilic head functions as a photosensitizer to absorb sunlight, and its hydrophobic tail acts as an inducer for self-assembly.

When it is placed in water, the nanomicelles self-assemble due to intermolecular hydrogen bonding between the water molecules and the tails. Adding a cobalt catalyst results in photocatalytic hydrogen production and carbon dioxide reduction, resulting in the production of hydrogen and methane.

Using advanced imaging techniques and ultrafast spectroscopy, the team unveiled the atomic features of the innovative photosensitizer. They discovered that the special structure of the nanomicelle’s hydrophilic head, along with the hydrogen bonding between water molecules and the nanomicelle’s tail, make it a stable, water-compatible artificial photosensitizer, solving the conventional instability and water-incompatibility problem of artificial photosynthesis. The electrostatic interaction between the photosensitizer and the cobalt catalyst, and the strong light-harvesting antenna effect of the nanomicelle improved the photocatalytic process.In the experiment, the team found that the methane production rate was more than 13,000 μmol h?1 g?1, with a quantum yield of 5.6% over 24 hours. It also achieved a highly efficient solar-to-fuel efficiency rate of 15%, surpassing natural photosynthesis.

Most importantly, the new artificial photocatalytic system is economically viable and sustainable, as it doesn’t rely on expensive precious metals. “The hierarchical self-assembly of the system offers a promising bottom-up strategy to create a precisely controlled, high-performance artificial photocatalytic system based on cheap, Earth-abundant elements, like zinc and cobalt porphyrin complexes,” said Professor Ye.

Professor Ye also commented he believes the latest discovery will benefit and inspire the rational design of future photocatalytic systems for carbon dioxide conversion and reduction using solar energy, contributing to the goal of carbon neutrality.