Surficial redox reactions play an essential role in photocatalytic water splitting, and are closely related to the surface properties of a specific photocatalyst. In this work, using monoclinic BiVO₄ decahedral single crystals as a model photocatalyst, we report on the interrelationship between the photocatalytic activity and the surficial reaction sites for charge-carrier consumption. By controlled hydrothermal synthesis, the ratio of {010} to {110} facets on BiVO₄, which respectively serve as reductive and oxidative sites, is carefully tailored. Our results show that superior photocatalytic water oxidation could be obtained on BiVO₄ decahedrons with a medium ratio of reductive/oxidative sites and that efficient overall water splitting could be achieved via further modification of appropriate cocatalysts in Z-scheme system. The excellent photocatalytic performance is attributed to the accelerated selective redox reactions by realizing balanced charge-carrier consumption, which provides insightful guidance for prospering photocatalytic reactions in energy conversion.