A Precious‐Metal‐Free Hybrid Electrolyzer for Alcohol Oxidation Coupled to CO2‐to‐Syngas Conversion

• Published in: Angewandte Chemie 2020-09, Vol.132 (36), p.15763-15771
• Main Authors: Bajada, Mark A., Roy, Souvik, Warnan, Julien, Abdiaziz, Kaltum, Wagner, Andreas, Roessler, Maxie M., Reisner, Erwin
• Format: Article
• Language: English
• Subjects: alcohols; Anodizing; Carbon dioxide; Carbon nanotubes; catalyst immobilization; Cathodes; Chemistry; Cobalt; Coupling (molecular); electrocatalysis; Electrocatalysts; Electrolysis; energy conversion; Glyceraldehyde; Glycerol; Indium tin oxides; Nanotechnology; Nanotubes; Oxidation; Substrates; Synthesis gas; Tin
• ISSN: 0044-8249; 1521-3757
• DOI: 10.1002/ange.202002680

Electrolyzers combining CO2 reduction (CO2R) with organic substrate oxidation can produce fuel and chemical feedstocks with a relatively low energy requirement when compared to systems that source electrons from water oxidation. Here, we report an anodic hybrid assembly based on a (2,2,6,6‐tetramethylpiperidin‐1‐yl)oxyl (TEMPO) electrocatalyst modified with a silatrane‐anchor (STEMPO), which is covalently immobilized on a mesoporous indium tin oxide (mesoITO) scaffold for efficient alcohol oxidation (AlcOx). This molecular anode was subsequently combined with a cathode consisting of a polymeric cobalt phthalocyanine on carbon nanotubes to construct a hybrid, precious‐metal‐free coupled AlcOx–CO2R electrolyzer. After three‐hour electrolysis, glycerol is selectively oxidized to glyceraldehyde with a turnover number (TON) of ≈1000 and Faradaic efficiency (FE) of 83 %. The cathode generated a stoichiometric amount of syngas with a CO:H2 ratio of 1.25±0.25 and an overall cobalt‐based TON of 894 with a FE of 82 %. This prototype device inspires the design and implementation of nonconventional strategies for coupling CO2R to less energy demanding, and value‐added, oxidative chemistry. Inspirational device: A molecularly engineered electrolyzer was constructed for the selective oxidation of glycerol to glyceraldehyde, with a turnover number (TON) of ≈1000 and a Faradaic efficiency (FE) of 83 %, coupled with aqueous CO2 reduction to generate a stoichiometric amount of syngas, with a CO:H2 ratio of 1.25±0.25, an overall TON of 894 and FE of 82 %.