空気から作るソーラー燃料への一歩(A step towards solar fuels out of thin air)


EPFLの化学技術者たちは、透明で多孔質の新しい電極の上に、空気中の水分を採取して水素燃料に変換することができる、太陽光発電の人工葉を発明した。この半導体ベースの技術は、拡張性があり、調製が容易です。 EPFL chemical engineers have invented a solar-powered artificial leaf, built on a novel electrode which is transparent and porous, capable of harvesting water from the air for conversion into hydrogen fuel. The semiconductor-based technology is scalable and easy to prepare.

2023-01-04 スイス連邦工科大学ローザンヌ校(EPFL)

 空気中から水を採取し、太陽エネルギーだけで水素燃料を供給する装置は、何十年にもわたって研究者の夢であった。今回、EPFLの化学エンジニアであるKevin Sivula氏と彼のチームは、この夢の実現に向けた重要な一歩を踏み出しました。半導体ベースの技術と、2つの重要な特徴をもつ新しい電極を組み合わせた、独創的かつシンプルなシステムを開発しました。多孔質であるため空気中の水と最大限に接触し、透明であるため半導体コーティングが太陽光に最大限に露出する。このデバイスに太陽光を当てるだけで、空気中の水分を取り込み、水素ガスを発生させることができます。この成果は、2023年1月4日付のAdvanced Materialsに掲載されました。


気相光電気化学水素製造用透明多孔質導電性基材 Transparent Porous Conductive Substrates for Gas-Phase Photoelectrochemical Hydrogen Production

Marina Caretti, Elizaveta Mensi, Raluca-Ana Kessler, Linda Lazouni, Benjamin Goldman, Loï Carbone, Simon Nussbaum, Rebekah A. Wells, Hannah Johnson, Emeline Rideau, Jun-ho Yum, Kevin Sivula
Advanced Materials  Published: 28 November 2022


Gas diffusion electrodes are essential components of common fuel and electrolysis cells but are typically made from graphitic carbon or metallic materials, which do not allow light transmittance and thus limit the development of gas-phase based photoelectrochemical devices. Herein, the simple and scalable preparation of F-doped SnO2 (FTO) coated SiO2 interconnected fiber felt substrates is reported. Using 2–5 µm diameter fibers at a loading of 4 mg cm−2, the resulting substrates have porosity of 90%, roughness factor of 15.8, and Young’s Modulus of 0.2 GPa. A 100 nm conformal coating of FTO via atmospheric chemical vapor deposition gives sheet resistivity of 20 ± 3 Ω sq−1 and loss of incident light of 41% at illumination wavelength of 550 nm. The coating of various semiconductors on the substrates is established including Fe2O3 (chemical bath deposition), CuSCN and Cu2O (electrodeposition), and conjugated polymers (dip coating), and liquid-phase photoelectrochemical performance commensurate with flat FTO substrates is confirmed. Finally, gas phase H2 production is demonstrated with a polymer semiconductor photocathode membrane assembly at 1-Sun photocurrent density on the order of 1 mA cm−2 and Faradaic efficiency of 40%.

太陽熱水素製造用有機半導体光電面の安定性の確立 Establishing Stability in Organic Semiconductor Photocathodes for Solar Hydrogen Production

Liang Yao, Néstor Guijarro, Florent Boudoire, Yongpeng Liu, Aiman Rahmanudin, Rebekah A. Wells, Arvindh Sekar, Han-Hee Cho, Jun-Ho Yum, Florian Le Forma, and Kevin Sivula
Journal of the American Chemical Society  Published:April 9, 2020


As organic semiconductors attract increasing attention to application in the fields of bioelectronics and artificial photosynthesis, understanding the factors that determine their robust operation in direct contact with aqueous electrolytes becomes a critical task. Herein we uncover critical factors that influence the operational stability of donor:acceptor bulk heterojunction photocathodes for solar hydrogen production and significantly advance their performance under operational conditions. First, using the direct photoelectrochemical reduction of aqueous Eu3+ and impedance spectroscopy, we determine that replacing the commonly used fullerene-based electron acceptor with a perylene diimide-based polymer drastically increases operational stability and identify that limiting the photogenerated electron accumulation at the organic/water interface to values of ca. 100 nC cm–2 is required for stable operation (>12 h). These insights are extended to solar-driven hydrogen production using MoS3, MoP, or RuO2 water reduction catalyst overlayers where it is found that the catalyst morphology strongly affects performance due to differences in charge extraction. Optimized performance of bulk heterojunction photocathodes coated with a MoS3:MoP composite gave 1 Sun photocurrent density up to 8.7 mA cm–2 at 0 V vs RHE (pH 1). However, increased stability was gained with RuO2 where initial photocurrent density (>8 mA cm–2) deceased only 15% or 33% during continuous operation for 8 or 20 h, respectively, thus demonstrating unprecedented robustness without a protection layer. This performance represents a new benchmark for organic semiconductor photocathodes for solar fuel production and advances the understanding of stability criteria for organic semiconductor/water-junction-based devices.