Photoreduction of inorganic carbon(+IV) by elemental sulfur: Implications for prebiotic synthesis in terrestrial hot springs

Yanzhang Li; Yan Li; Yi Liu; Yifu Wu; Junqi Wu; Bin Wang; Huan Ye; Haoning Jia; Xiao Wang; Linghui Li; Meixiang Zhu; Hongrui Ding; Yong Lai; Changqiu Wang; Jeffrey Dick; Anhuai Lu

doi:10.1126/sciadv.abc3687

Photoreduction of inorganic carbon(+IV) by elemental sulfur: Implications for prebiotic synthesis in terrestrial hot springs

Sci Adv. 2020 Nov 18;6(47):eabc3687. doi: 10.1126/sciadv.abc3687. Print 2020 Nov.

Authors

Yanzhang Li^{1

2}, Yan Li^{3

2}, Yi Liu^{1

2}, Yifu Wu^{1

2}, Junqi Wu^{1

2}, Bin Wang⁴, Huan Ye^{1

2}, Haoning Jia^{1

2}, Xiao Wang^{1

2}, Linghui Li^{1

2}, Meixiang Zhu^{1

2}, Hongrui Ding^{1

2}, Yong Lai^{1

2}, Changqiu Wang^{1

2}, Jeffrey Dick⁵, Anhuai Lu^{3

2

5}

Affiliations

¹ Beijing Key Laboratory of Mineral Environmental Function, School of Earth and Space Sciences, Peking University, Beijing 100871, People's Republic of China.
² The Key Laboratory of Orogenic Belts and Crustal Evolution, School of Earth and Space Sciences, Peking University, Beijing 100871, People's Republic of China.
³ Beijing Key Laboratory of Mineral Environmental Function, School of Earth and Space Sciences, Peking University, Beijing 100871, People's Republic of China. liyan-pku@pku.edu.cn ahlu@pku.edu.cn.
⁴ Sinopec Beijing Research Institute of Chemical Industry, Beijing 100013, People's Republic of China.
⁵ The Key Laboratory of Metallogenic Prediction of Nonferrous Metals and Geological Environment Monitoring, School of Geosciences and Info-Physics, Central South University, Changsha 410083, People's Republic of China.

Abstract

Terrestrial hydrothermal systems have been proposed as alternative birthplaces for early life but lacked reasonable scenarios for the supply of biomolecules. Here, we show that elemental sulfur (S⁰), as the dominant mineral in terrestrial hot springs, can reduce carbon dioxide (CO₂) into formic acid (HCOOH) under ultraviolet (UV) light below 280 nm. The semiconducting S⁰ is indicated to have a direct bandgap of 4.4 eV. The UV-excited S⁰ produces photoelectrons with a highly negative potential of -2.34 V (versus NHE, pH 7), which could reduce CO₂ after accepting electrons from electron donors such as reducing sulfur species. Simultaneously, UV light breaks sulfur bonds, benefiting the adsorption of charged carbonates onto S⁰ and assisting their photoreduction. Assuming that terrestrial hot springs covered 1% of primitive Earth's surface, S⁰ at 10 μM could have produced maximal 10⁹ kg/year HCOOH within 10-cm-thick photic zones, underlying its remarkable contributions to the accumulation of prebiotic biomolecules.

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