Advances in Hydrogen-Driven Bicarbonate Conversion to Formic Acid and Formate Salts.

Abstract

According to a January 2025 report by the UK Met Office, carbon dioxide (CO₂) levels are expected to reach 429.6 ppm in May, marking the highest concentration in over 2 million years. This alarming rise has intensified global efforts to mitigate climate change through carbon capture and utilization (CCU) technologies. A promising strategy is converting CO₂ into valuable chemicals such as formic acid and formate salts. Formic acid, in particular, is seen as a potential hydrogen carrier, addressing challenges in hydrogen storage and transport. However, the direct hydrogenation of CO₂ to formic acid is thermodynamically challenging due to the high stability. To overcome these barriers, researchers have explored alternative pathways, such as the reduction of bicarbonate (HCO₃ ^-), which is more reactive and easier to handle. Bicarbonate can be sourced from CO₂-rich streams like flue gases or seawater, simplifying capture and conversion. This review explores hydrogen-driven bicarbonate conversion via catalytic methods: electrocatalysis, thermocatalysis, photocatalysis, homogeneous, and enzymatic catalysis. Each uses distinct energy inputs and offers unique advantages. While electrocatalysis shows 90% Faradaic efficiency, photocatalysis and enzymatic approaches remain limited by quantum yields and scalability. The review outlines key advances, challenges, and future directions to enhance these technologies for a sustainable, carbon-neutral future.