Leiden Institute of Chemistry, Leiden University , P.O. Box 9502, 2300 RA Leiden, The Netherlands.
J Am Chem Soc. 2017 Feb 8;139(5):2030-2034. doi: 10.1021/jacs.6b12008. Epub 2017 Jan 30.
A seemingly catalytically inactive electrode, boron-doped diamond (BDD), is found to be active for CO and CO reduction to formaldehyde and even methane. At very cathodic potentials, formic acid and methanol are formed as well. However, these products are the result of base-catalyzed Cannizzaro-type disproportionation reactions. A local alkaline environment near the electrode surface, caused by the hydrogen evolution reaction, initiates aldehyde disproportionation promoted by hydroxide ions, which leads to the formation of the corresponding carboxylic acid and alcohol. This phenomenon is strongly influenced by the electrolyte pH and buffer capacity and not limited to BDD or formaldehyde, but can be generalized to different electrode materials and to C and C aldehydes as well. The importance of these reactions is emphasized as the formation of acids and alcohols is often ascribed to direct CO reduction products. The results obtained here may explain the concomitant formation of acids and alcohols often observed during CO reduction.
一种看似无催化活性的电极，硼掺杂金刚石（BDD），被发现对 CO 和 CO 还原为甲醛甚至甲烷具有活性。在非常阴极化的电位下，甲酸和甲醇也会形成。然而，这些产物是碱催化 Cannizzaro 型歧化反应的结果。由析氢反应引起的电极表面附近的局部碱性环境，引发了由氢氧根离子促进的醛歧化反应，导致相应的羧酸和醇的形成。这种现象强烈地受到电解质 pH 值和缓冲能力的影响，不仅限于 BDD 或甲醛，也可以推广到不同的电极材料以及 C 和 C 醛。这些反应的重要性被强调，因为酸和醇的形成通常归因于直接的 CO 还原产物。这里得到的结果可以解释在 CO 还原过程中经常观察到的酸和醇的同时形成。
