One example is the chalcopyrite minerals (Cu1+xFe1–xS2) obtained from the Snow Chimney black smoker vent of the Mariner field in the southern Lau Basin.5 Due to their surface microstructure, these minerals exhibited a combination of low thermal conductivity and high electric conductivity, leading to thermoelectric properties. All are living under extreme pressure and temperature changes. A) Faradaic efficiencies of CO2 reduction on FeNi sulfide. The difference of optimum pH for each reaction results in a pH window which can enhance the selectivity for a desired reaction. Therefore, regulating selectivity boils down to how efficiently the catalyst can transfer electrons and protons to specific atoms to generate desired chemical compounds. Bacteria at hydrothermal vents inhabit almost everything: rocks, the seafloor, even the inside of animals like mussels. Temperature gradients are an under-utilized source of energy with which to drive chemical reactions. Chemical reactions that occur at vents are also considered, including organic synthesis and the formation of metal sulfides. Therefore, at least in the case of our lab‐synthesized FeNi sulfide, the driving force from the temperature and pH difference is clearly sufficient for CO2 reduction,10 giving insight into how the first organic molecules necessary for prebiotic life may have originated due to the catalytic activities of the inorganic hydrothermal vent.10,18, As to how this driving force is used to reduce CO2, it is worth noting that the thermodynamics become more favorable upon transferring more electrons (Table 1). The benefits of the aforementioned strategies to boost the electrochemical driving force were observed directly in our previous studies using iron sulfides.10 These materials are a major component of the modern black smoker type chimneys and perhaps existed in ancient hydrothermal vents.56,57,59 They are also known to exhibit electrocatalytic activity to reduce CO2 to CO and CH4 (Figure 4A). The Minami-Ensei knoll is located in a rifting center in the northern Okinawa Trough (Chiba et al., 1993). Efficient utilization of energy is an important aspect of any applied chemical process.1,2 In industrial chemical synthesis or energy conversion, energy efficiency is one of the most influential parameters of economical and industrial feasibility.1,2 From a biological standpoint, energy efficiency can dictate what species can fill an environmental niche,3 which in turn affects evolution.4 From a number of perspectives then, it is important to understand the factors which control how thermodynamic driving forces (energy availability) can be utilized to drive chemical reactions more efficiently, especially those from diffuse and fluctuating sources. This heated seawater (350-450°) dissolves large amounts of minerals. These calculations suggest that seafloor hydrothermal vent fluids contain as much as 0.5–10 nmol/kg Au. The respiratory plume is extended into … %PDF-1.5 %���� Contributors: Nadine Le Bris (Convenor), Sophie Arnaud-Haond, Stace Beaulieu, Erik Cordes, Ana Hilario, Alex Rogers, lead member), Saskia van de Gaever At a hydrothermal vent, the pH varies depending on the degree of mixing and diffusion, which would expose active sites along the chimney wall to different local pH (Figure 6). However, another important discrepancy between the hydrothermal fluid and the seawater is the temperature. On the other hand, at an elevated temperature of 500 K, such as that observed in the Iheya North hydrothermal field of the Okinawa Trough, Japan11 this value increases to 100 mV. If we imagine a scenario where CO2 is reduced by mixing directly with the reductive hydrothermal fluid, there is no difference in the temperature or pH between the vent fluid and the CO2, because they coexist in the same environment.20,50 In other words, several hundred mVs worth of reductive energy is lost, purely because the single chamber system fails to harvest the thermodynamic disequilibria between the vent fluid and the sea water. The authors declare no conflict of interest. Hydrothermal Vents photo courtesy of Schmidt Ocean Institute. In light of the fact that many industrial process require high temperature,42,46 the efficient utilization of heat at the deep sea hydrothermal vent may provide an important blue print. 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