Boosting multi-hole water oxidation catalysis on hematite photoanodes under low bias

Photoelectrochemical (PEC) water oxidation reaction has attracted considerable attention in recent years because of its importance in solar energy conversion. For such a sluggish four-hole and four-proton transfer reaction in a long timescale of ms–s, more and more studies have shown that the accumulation of multiple surface-trapped holes (e.g., high-valent iron oxo on hematite surfaces) or "oxidizing equivalents" is a prerequisite for efficient PEC water oxidation process. Previous PEC water oxidation studies commonly apply high potentials (>1.2 VRHE) to achieve this key. But how to complete multi-hole transfer under low bias (near the onset potential) remains unknown.