All Electrochemical Synthesis of Performic Acid Starting from CO₂, O₂, and H₂O

Driven by anthropogenic climate change, innovative approaches to defossilize the chemical industry are required. Herein, the first all‐electrochemical feasibility study for the complete electrosynthesis of the strong oxidizer and effective disinfectant performic acid is presented. Its synthesis is achieved solely from CO 2 , O 2 , and H 2 O in a two‐step process. Initially, CO 2 is electrochemically reduced to formate employing Bi 2 O 3 ‐based gas diffusion electrodes in a phosphate‐buffered electrolyte. Thereby, high formate concentration (500.7 ± 0.6 mmol L −1 ) and high Faradaic efficiency (86.3 ± 0.3%) are achieved at technically relevant current density (150 mA cm −2 ). Subsequently, the formate acts as (storable) feed electrolyte for the second electrolysis step. Employing carbon‐based gas diffusion electrodes, O 2 is reduced to H 2 O 2 and performic acid is directly formed in situ. As before, high H 2 O 2 concentration (1.27 ± 0.06 mol L −1 ) and high Faradaic efficiency (85.3 ± 5.4%) are achieved. Furthermore, performic acid concentration suitable for disinfection is obtained (82 ± 11 mmol L −1 ). In summary, this innovative feasibility study highlights the potential of combining electrochemical CO 2 reduction with H 2 O 2 electrosynthesis, which could provide sustainable access to performic acid in the future.