Hydrothermal Conditions Enhance Electrochemical CO2 Reduction Reaction: A Sustainable Path to Efficient Carbon Recycling

Abstract

In converting CO₂ into useful chemical starting materials, the electrochemical CO₂ reduction reaction (CO2RR) promises to be a major carbon-utilization strategy, contributing to a carbon-neutral society. These are proposed using hydrothermal conditions—characterized by high temperature and high pressure—to address the challenges of CO2RR. Technology assessment revealed that the additional energy to create hydrothermal conditions doesnot increase the overall energy demand for chemical production, and the CO₂ emissions from methanol production through hydrothermal electrochemical CO2RR can be negative with the photovoltaic electricity and waste heat supply. Moreover, These experimentally demonstrated promising improvements in the CO2RR process using hydrothermal conditions and elucidated the specific roles of temperature and pressure in promoting CO2RR. An increase in the process temperature to 150 °C, improves the CO₂ diffusion coefficient in water, resulting in the enhancement of current density and the reduction of activation overpotential for CO2RR. On the other hand, the pressurization by CO₂ can prevent the decrease in CO₂ solubility under high-temperature conditions, keeping a high selectivity of CO2RR. These findings indicate a plausible avenue for the efficient recycling of CO₂ and its integration into the carbon cycle, marking a significant stride toward a sustainable, zero-emission society.