Mg-doped TaN nanorods coated with a conformal CoOOH layer for water oxidation: Bulk and surface dual modification of photoanodes

Charge separation/transfer and photocorrosion are two major factors limiting the photoelectrochemical (PEC) applications of the TaN photocatalyst. Herein, we have fabricated TaN single-crystal nanorods with Mg doping by flux-assisted crystal growth, aiming to shorten the charge transport distance and increase the electrical conductivity. The optimized Mg-doped TaN photoanodes exhibit an unprecedented PEC water splitting activity with an AM 1.5G photocurrent of 1.5 mA cm at 1.23 V. The high performance is attributed to the fact that the bulk modification, Mg doping, can induce oxygen-impurity surface states as effective electron trap centers, thus increasing the electrical conductivity of TaN and charge separation efficiency. After a conformal surface modification with CoOOH by a simple electrodeposition method as a water oxidation electrocatalyst to improve the hole extraction and reaction kinetics, the Mg-doped TaN photoanodes afford an over 4-fold increase in photocurrent (ca. 6.5 mA cm at 1.23 V) and about 70% retention of the initial photocurrent after 70 min irradiation at 1.0 V. Our results testify that the bulk and surface co-modification is an effective route to develop high-performance PEC water splitting devices.