Molecular Catalysts Modified Fe₂O₃ For Photoelectrocatalytic Water Oxidation

Photoelectrochemical（PEC）water splitting is a promising approach for solar energy conversion.In overall water splitting,water oxidation is recognized as the thermodynamic and kinetic bottleneck.Therefore,the construction of highly efficient photoanode for oxygen evolution is crucial for an efficient PEC cell.Fe₂O₃（hematite）is a tyoe of traditional photoanode materials,which has the advantages of suitable band gap,large theoretical photocurrent density,good optical stability and high abundance.However,it suffers from short hole diffusion length,poor charge transport performance and slow interface dynamics.In order to improve the performance of Fe₂O₃photoanode,in this study,we integrate a thin layer of Fe OOH on the Fe₂O₃ photoanode and utilize the electropolymerization method to load Ru（bda）（vpy）catalyst on the surface of Fe₂O₃/Fe OOH.Fe₂O₃/Fe OOH/poly-Ru（bda）（vpy）ternary hybrid photoanode was successfully constructed for PEC water splitting,in which Fe OOH replicates the role of tyrosine residue in PSII as an efficient electron transfer mediator.The ternary hybrid photoanode produced a 2.4 times higher photocurrent density than that of previously reported Fe₂O₃/poly-Ru（bda）（vpy）under simulated sun-light irradiation,and displayed a negative shift on the onset potential by100 m V.Furthermore,the long-term constant voltage electrolysis proved that the introduction of Fe OOH can significantly enhance the stability of the hybrid electrode.Transient fluorescence spectroscopy and electrochemical impedance spectroscopy show that the water splitting performance of the hybrid electrode could be effectively improved by Fe OOH as an efficient electron and hole transfer relay between Fe₂O₃substrate and Ru（bda）（vpy）.On the basis of the above hybrid photoanode,a hybrid PEC water splitting system Fe₂O₃/Fe OOH/bpmen-Co（bpmen=N,N’-dimethyl-N,N’-bis-（pyridin-2-ylmethyl）-1,2-diaminoethane）based on non-noble metal water oxidation catalyst was constructed to reduce the cost of the artificial synthetic system.Photoelectrochemical experiments showed that the hybrid system exhibited good PEC performance and excellent stability,indicating that this strategy could be extended to other PEC water splitting systems.The above results are of importance for the ratinal design of highly efficient articifical photosynthetic systems.