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.

有人提出将陆地热液系统作为早期生活的替代发源地，但缺乏提供生物分子的合理方案。在这里，我们表明元素硫（S ⁰）作为陆地温泉中的主要矿物，可以在280 nm以下的紫外线（UV）下将二氧化碳（CO ₂）还原为甲酸（HCOOH）。半导体S ⁰被示为具有4.4eV的直接带隙。紫外线激发的S ⁰产生具有-2.34 V的高负电势（相对于NHE，pH 7）的光电子，这可以减少CO ₂接受来自电子供体的电子，例如还原硫物种。同时，紫外线会破坏硫键，有利于带电荷的碳酸盐在S ⁰上的吸附并有助于其光还原。假设地面温泉覆盖了原始地球表面的1％，则10μM的S ⁰可能在10厘米厚的光生带内产生最大10 ⁹ kg /年的HCOOH，这是其对益生元生物分子积累的显着贡献。