Anchoring a Molecular Iron Catalyst to Solar-Responsive WO3 Improves the Rate and Selectivity of Photoelectrochemical Water Oxidation

Molecular catalysts help overcome the kinetic limitations of water oxidation and generally result in faster rates for water oxidation than do heterogeneous catalysts. However, molecular catalysts typically function in the dark and therefore require sacrificial oxidants such as Ce4+ or S2O82– to provide the driving force for the reaction. In this Communication, covalently anchoring a phosphonate-derivatized complex, Fe­(tebppmcn)­Cl2 (1), to WO3 removes the need for a sacrificial oxidant and increases the rate of photoelectrochemical water oxidation on WO3 by 60%. The dual-action catalyst, 1-WO3, also gives rise to increased selectivity for water oxidation in pH 3 Na2SO4 (56% on bare WO3, 79% on 1-WO3). This approach provides promising alternative routes for solar water oxidation.分子催化剂可克服水氧化反应的动力学限制，通常较多相催化剂具备更快的水氧化反应速率。然而，分子催化剂通常仅能在黑暗环境中发挥作用，因此需要诸如四价铈（Ce⁴⁺）或过二硫酸根（S₂O₈²⁻）之类的牺牲性氧化剂为反应提供驱动力。本研究通讯中，将膦酸酯修饰的配合物Fe(tebppmcn)Cl₂（记为化合物1）共价锚定至三氧化钨（WO₃）表面，不仅无需使用牺牲性氧化剂，还将WO₃表面的光电化学水氧化反应速率提升了60%。该双功能催化剂1-WO₃在pH=3的硫酸钠（Na₂SO₄）电解液中，还可提升水氧化反应的选择性：裸WO₃表面的选择性为56%，而1-WO₃表面可达79%。该策略为太阳能驱动的水氧化反应提供了极具潜力的替代路径。