How has nature handled electron flow for carbon fixation? We know the mechanism of carbon fixation taking place inside chloroplast. At least, we know the framework of its action and function. Parallelly important, yet relatively unknown processes are carbon fixation taking place in deep-sea hydrothermal environments, which contain low levels or no solar radiation. In such environments, nature has to develop the systems to harvest geochemical and geothermal energy to generate high-energy electrons needed for carbon fixation. Yet, how nature utilizes temperature and chemical gradient fostered by geological settings remains largely unknown. In this talk, based on our findings of electrical current generation across a black smoker hydrothermal vent,^[1,2] together with thermoelectrical conversion by deep-sea minerals,^[3] I provide the new energetic underpinning of carbon fixation: de-coupled electron and heat transfer at deep-sea hydrothermal vents ^[4,5]. As catalysis at the deep-sea vent may tightly link with the origin and evolution of life, I provide the perspective to predict the first engine that drives the life emergence and fosters life complexity.

(1) R. Nakamura, et al. Angew. Chem. Int. Ed., 49, 7692 (2010). (2) M. Yamamoto, et al. Angew. Chem. Int. Ed., 52, 10758 (2013). (3) R. Ang, et al. Angew. Chem. Int. Ed., 54, 12909 (2015). (4) A. Yamaguchi, et al. Electrochim. Acta, 141, 311 (2014). (5) A. Yamaguchi, et al. Springer, Chapter 4.3.2. (2016).