Hematite decorated with nanodot-like cobalt (oxy)hydroxides for boosted photoelectrochemical water oxidation

CoOOH nanodots decorated hematite (CoOOH/Fe2O3) photoanode was successfully fabricated. The CoOOH/Fe2O3 exhibits a high photocurrent density of 1.92 mA cm−2 at 1.23 V vs. RHE, which is ca. 2.6 times to that of bare Fe2O3, and a ca. 110 mV cathodic shift of the onset potential. CoOOH plays important roles that suppress the surface recombination and improve the charge transfer. [Display omitted] •CoOOH nanodot was rationally designed and in-situ decorated on Fe2O3 photoanode.•CoOOH/Fe2O3 exhibited superior photoelectrochemical activity for water oxidation.•CoOOH could suppress charge recombination by passivating the surface states of Fe2O3.•CoOOH provided active sites and facilitated the charge transfer for water oxidation. Photoelectrochemical (PEC) water splitting has been considered as an alternative process to produce green hydrogen. However, the energy conversion efficiency of PEC systems was still limited by the inefficient photoanode. Cocatalysts decoration is regarded as an efficient strategy for improving PEC performance of photoanode. In this work, nanodot-like cobalt (oxy)hydroxides was rationally decorated on hematite to fabricate CoOOH/Fe2O3 photoanode. The resulted CoOOH/Fe2O3 exhibits a high photocurrent density of 1.92 mA cm−2 at 1.23 V vs. RHE, which is 2.6 times than that of bare Fe2O3. In addition, the onset potential displays a cathodic shift of ca. 110 mV, indicating that CoOOH can efficiently accelerate water oxidation kinetics over Fe2O3. The comprehensive PEC and electrochemical characterizations reveal that CoOOH could not only provide abundant accessible Co active sites for water oxidation, but also could passivate the surface states of Fe2O3, thus increase the carrier density and decrease the interfacial resistance. As a result, the PEC water oxidation performance over Fe2O3 was significantly boosted. This work supports that the roles of CoOOH cocatalyst is generic and such CoOOH could be used for other semiconductor-based photoanodes for outstanding PEC water splitting performance.