Coupling multifunctional ZnCoAl-layered double hydroxides on Ti-FeO photoanode for efficient photoelectrochemical water oxidation.

The efficiency of photoelectrochemical (PEC) water splitting is hindered by the slow kinetics of the oxygen evolution reaction (OER). This study developed a composite photoanode for water oxidation by incorporating ternary LDHs (ZnCoAl-LDH) onto Ti-FeO as a cocatalyst. The ZnCoAl-LDH/Ti-FeO photoanode achieved a photocurrent density of 3.51 mA/cm at 1.23 V vs. RHE, which is 9.8 times higher than that of bare Ti-FeO. Through a series of characterizations, the synergistic effects among the three metals were revealed. Furthermore, the addition of Zn can induce the formation of more high-valent Co, increasing the conductivity of CoAl-LDH and significantly reducing the surface charge transfer resistance. These advantages significantly enhance the injection efficiency of ZnCoAl-LDH/Ti-FeO (82 %), thereby accelerating the OER kinetics of Ti-FeO. Our work introduces new approaches for selecting photoelectrochemical cocatalysts and designing high-performance photoanodes for water splitting.