Unveiling the influence of 5,10,15,20-tetrakis (4-carboxyl phenyl) porphyrin on the photogenerated charge behavior and photoelectrochemical water oxidation of hematite photoanode

Coupling porphyrins with semiconductors is demonstrated as one of effective means to facilitate the separation of photogenerated charge in dye-sensitized solar cells as well as photocatalytic hydrogen production. However, there are limited reports about exploring the effect of porphyrin on the behavior of photogenerated charges and photoelectrochemical (PEC) water oxidation performance. Herein, we have built a hybrid photoanode containing Ti doped α-Fe2O3 (Ti-Fe2O3), 5,10,15,20-tetrakis (4-carboxyl phenyl) porphyrin (H2TCPP) and cobalt phosphate (CoPi) cocatalyst. Because of the appropriate band alignment of Ti-Fe2O3, H2TCPP and CoPi, the photogenerated holes are transferred directionally from Ti-Fe2O3 to CoPi across H2TCPP, which boosts the separation efficiency of CoPi/H2TCPP/Ti-Fe2O3 in turn. Meanwhile, CoPi/H2TCPP/Ti-Fe2O3 possesses higher injection efficiency as well. Under the double guarantee of high separation efficiency and injection efficiency, CoPi/H2TCPP/Ti-Fe2O3 yields an impressive photocurrent density of 1.84 mA/cm2 at 1.23 V vs. reversible hydrogen electrode (RHE), which is much higher than that of CoPi/Ti-Fe2O3. This structure design describes an appealing maneuver to facilitate the directed migration of photogenerated charges and then enhance the PEC water oxidation performance.