以釩酸鉍光陽極進行小分子的光電化學氧化反應

Abstract

光電催化有機合成（photoelectrocatalytic organic synthesis, PECOS）因具備溫和的反應條件與獨特的產物選擇性，被認為是環保且具有潛力有機合成策略。然而，儘管具備這些優勢，對固液界面反應機制的理解仍然不足，限制了其更廣泛的應用。本研究中，我們以單斜白鎢礦型釩酸鉍（bismuth vanadate, BiVO4）作為光陽極，進行兩項光電催化反應。第一部分中，成功透過間接氧化機制將苯甲醇選擇性氧化為苯甲醛。研究結果顯示，反應效率受限於氧化還原介體－N-羥基琥珀醯亞胺（NHS）在電極表面的吸附，該吸附會形成有害的表面態，導致光生載子複合，並抑制NHS的完全再生。經鉬摻雜於BiVO4後，可有效降低表面態的生成，顯著提升催化效率。在最佳條件下，苯甲醛的生成速率達19.1 μmol cm-2 h-1，且選擇性與法拉第效率均接近100%。動力學分析亦顯示，鉬摻雜電極具有較長的吸附時間常數，佐證其產率提升之原因。 第二部分則以BiVO4光陽極直接氧化鄰-三聯苯（o-terphenyl），成功驅動分子內碳－碳鍵形成反應，合成三亞苯（triphenylene）。此為首次在光電化學條件下成功實現朔爾反應（Scholl reaction），為多環芳烴（polycyclic aromatic hydrocarbons）的綠色合成提供了新的途徑。這些研究結果不僅展現光電化學在有機合成中的應用潛力，也強調了對固液界面反應機制深入理解的重要性，為未來光電化學有機反應的設計提供了重要參考。

Photoelectrocatalytic organic synthesis (PECOS) has emerged as a promising approach for sustainable organic synthesis due to its mild reaction conditions and unique product selectivity. Despite these advantages, limited understanding of interfacial behavior and efficiency loss mechanisms remains a major challenge. In this study, monoclinic scheelite-type bismuth vanadate (BiVO4) photoanodes were applied to two light-driven reactions. First, benzyl alcohol was selectively oxidized to benzaldehyde through an indirect oxidation pathway. The reaction efficiency was found to be limited by the specific adsorption of the redox mediator N-hydroxysuccinimide (NHS) on the BiVO4 surface, which induced detrimental surface states, promoted charge recombination, and suppressed complete regeneration of NHS. Molybdenum doping effectively reduced surface state density and improved catalytic performance, achieving a benzaldehyde formation rate of 19.1 μmol cm-2 h-1 with nearly 100% selectivity and Faradaic efficiency. Kinetic analysis showed longer adsorption time constants for Mo-doped electrodes, corroborating the enhancement in reaction yield. In the second part, BiVO4 was used to drive intramolecular C–C bond formation via direct oxidation of o-terphenyl, yielding triphenylene. This work represents the first successful demonstration of the Scholl reaction via PEC, offering a new sustainable route for synthesizing polycyclic aromatic hydrocarbons. Overall, this work highlights the potential of PEC in organic synthesis and underscores the importance of understanding interfacial mechanisms, providing valuable insights for the rational design of future PEC systems.