Photoelectric conversion of mineral coatings on planetary surfaces (source: phys.org)

With the support of the National Natural Science Foundation of China (No. 41230103, 41522201), the collaboration of Lu Anhuai, Li Yan and Ding Hongrui from School of Earth and Space Sciences, Peking University, with Liu Kaihui from School of Physicsand Michael F. Hochella Jr., Virginia Tech, USA, has achieved significant progress in the field of solar energy conversion by the photoelectric effect of minerals. Relevant research results were published online in Proceedings of the National Academy of Sciences (PNAS) on April 22nd, 2019, under the title of "Photoelectric Conversion on Earth's Surface via Widespread Fe-and Mn-mineral Coatings". Full text link: https://www.pnas.org/content/early/2019/04/16/1902473116.

 Both organic organisms and inorganic minerals on Earth's land are exposed to solar irradiation. Photosynthesis is known as the largest and most important solar energy absorption and transformation reaction on Earth’s surface. However, whether there are other types of solar energy collection and utilization systems in nature has rarely been mentioned and concerned before. Through in-depth observation and analysis of rock/soil samples in different weathering environments in China such as Gobi Desert, karst landform and red soil, it was found that the surface of rock/soil particles directly exposed to sunlight was generally covered by a layer of iron/manganese (hydroxide) oxide "mineral coating". By means of micro-area and in-situ photoelectric measurements, the distribution mapping of photoelectric signals on mineral coating thin section was obtained at micro-scale. It is found that only the ferromanganese-rich "mineral coating" region shows a significant photocurrent signal, while the substrate without ferromanganese component does not produce any photocurrent response. Natural "mineral coating" has stable and sensitive solar photon-photoelectron conversion ability, which confirms that solar light has also been acting on surface minerals, producing energy absorption and transformation phenomenon and non-classical photosynthesis.

 This discovery broadens our new understanding of natural solar energy utilization pathways, that is, natural inorganic minerals also have solar energy conversion and utilization systems equivalent to organic photosynthesis, and provides a new perspective for the study of the origin of photosynthesis system and artificial photosynthesis. After the publication of the results, many domestic and foreign news media, such as Phys.org, Scinexx of Germany, nplus 1 of Russia, Xinhua News Agency, Science Network, Guangming Daily, China Daily, Beijing Daily and today's headlines, reported this scientific achievement immediately.