新系统模拟光合作用过程，特别是紫色细菌的有效能量转移
太阳能转化为燃料的效率为15%，这种方法超过自然光合作用，并以令人印象深刻的速度产生甲烷
创新和可持续的过程利用廉价的、地球上丰富的元素，潜在地推进碳中和的目标
据油价网2023年8月12日报道，香港城市大学的一个研究小组最近开发了一种稳定的人工光催化系统，比自然光合作用更有效。新系统模拟天然叶绿体，利用光线将水中的二氧化碳转化为甲烷，后者是一种很有价值的燃料。这一有希望的发现可能有助于实现碳中和的目标。
光合作用是指植物和一些生物体内的叶绿体利用阳光、水和二氧化碳来产生食物或能量的过程。在过去的几十年里，许多科学家试图开发人工光合作用过程，将二氧化碳转化为碳中和燃料。
香港城市大学化学系副教授叶如泉教授是这项联合研究的负责人之一，他解释说：“然而，由于许多光敏剂或催化剂在水中降解，因此很难在水中转换二氧化碳。尽管人工光催化循环已被证明具有更高的内在效率，但在水中减少二氧化碳的低选择性和稳定性阻碍了它们的实际应用。”
香港城市大学、香港大学、江苏大学和中国科学院上海有机化学研究所的联合研究小组在《自然催化》杂志上发表的最新研究中，克服了这些困难，利用超分子组装方法创建了一个人工光合系统。它模仿了紫色细菌的捕光色素体(即含有色素的细胞)的结构，这种色素体在从太阳转移能量方面非常有效。
新的人工光合系统的核心是一种高度稳定的人工纳米胶束——一种可以在水中自组装的聚合物，具有亲水和疏水两端。纳米胶束的亲水头部作为光敏剂吸收阳光，其疏水尾部作为自组装的诱导剂。
当它被放入水中时，由于水分子和纳米胶束疏水尾部之间的分子间氢键，纳米胶束会自组装。添加钴催化剂可产生光催化制氢和二氧化碳还原，从而产生氢气和甲烷。
利用先进的成像技术和超快光谱学，该团队揭示了创新光敏剂的原子特征。他们发现，纳米胶束亲水头部的特殊结构，以及水分子与纳米胶束疏水尾部之间的氢键，使其成为一种稳定的、与水相容的人工光敏剂，解决了人工光合作用的传统不稳定性和水不相容问题。光敏剂与钴催化剂之间的静电相互作用以及纳米胶团的强捕光天线效应改善了光催化过程。在实验中，研究小组发现甲烷的产率超过13000微摩尔每克每小时，24小时的量子产率为5.6%。它还实现了高效的太阳能转化为燃料的效率，达到15%，超过了自然光合作用。
最重要的是，新的人工光催化系统在经济上是可行的和可持续的，因为这种新的人工光催化系统不依赖昂贵的贵金属。叶如泉教授说：“系统的分层自组装提供了一种有前途的自下而上的策略，可以创建一个精确控制的高性能人工光催化系统，这个系统基于廉价的、地球上丰富的元素，如锌和钴卟啉复合物。”
叶如泉教授还表示，他相信这一最新发现将有利于并启发未来利用太阳能进行二氧化碳转化和还原的光催化系统的合理设计，为实现碳中和的目标形成积极助力。
李峻 译自 油价网
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.
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