Department of Chemistry, Yale University, New Haven, CT 06520, USA.
Chem Soc Rev. 2017 Oct 16;46(20):6099-6110. doi: 10.1039/c7cs00314e.
Surface anchoring groups are needed to attach molecular units to photoanodes for photocatalytic water oxidation. The anchoring group must be hydrolytically stable and oxidation resistant under a variety of pH conditions. They must sometimes be electrically conducting for efficient light-induced electron injection from a photosensitizer to a metal oxide, but other times not conducting for accumulation of oxidizing equivalents on a water-oxidation catalyst. Commonly used anchors such as carboxylic acids and phosphonic acids have limited stability in aqueous environments, leading to surface hydrolysis and loss of catalytic function. More hydrolytically stable anchors, such as silatranes and hydroxamic acids, which are oxidation resistant and stable under acidic, neutral, and basic conditions, are more suitable for photoanode applications. Hydroxamic acids can be incorporated into dye molecules to give high electron injection efficiency due to their electrical conductivity and strong electronic coupling to the metal oxide surface. In contrast, silatranes, once bound as siloxanes, have diminished electronic coupling making them useful as catalyst anchors.
表面锚固基团用于将分子单元附着到光阳极上以进行光催化水氧化。锚固基团必须在各种 pH 条件下具有水解稳定性和抗氧化性。它们有时必须具有导电性，以便有效地将光致电子从光敏剂注入金属氧化物，但有时则不能导电，以免在水氧化催化剂上积累氧化当量。羧酸和膦酸等常用的锚固基团在水相环境中的稳定性有限，导致表面水解和催化功能丧失。更稳定的锚固基团，如硅烷三醇和偕氨肟酸，在酸性、中性和碱性条件下具有抗氧化性和稳定性，更适合用于光阳极应用。偕氨肟酸可以掺入染料分子中，由于其导电性和与金属氧化物表面的强电子耦合，可提供高的电子注入效率。相比之下，硅烷三醇一旦作为硅氧烷结合，电子耦合就会减弱，使其成为有用的催化剂锚固基团。
