Photoelectrochemical (PEC) water splitting of BiOI{001} nanosheets synthesized by a simple chemical transformation

• We prepared BiOI {001} by a chemical transformation using commercial bismuth oxide.
• BiOI exhibits stronger visible light absorbance in the preferred growth direction.
• The PEC water splitting evaluation was demonstrated to be more effective over BiOI than Bi2O3.
• UPS reveals experimentally the exact VB and CB energy positions of BiOI.

BiOI nanosheets were successfully prepared by a simple chemical transformation technique. The group theory analysis illustrated that the three vibrational modes (A1g, B1g and 3Eg) of BiOI with a tetragonal structure are Raman active, and the A1g and B1g bands were found in the observable range. The TEM results signified that BiOI possess a tetragonal crystal structure with exposed {001} facets, which is favorable to aggrandize the visible-light photocatalytic phenomenon. The photocatalytic property of BiOI and the commercial Bi2O3 was investigated by the photoelectrochemical (PEC) water splitting process under visible light irradiation. The BiOI produces a photocurrent of 6.56 μA cm−2 (1.23 V vs. reversible hydrogen electrode (RHE)) for PEC water oxidation at pH 6.6, which is partly attributed to the strong visible light absorbance along a or b direction. The experimental outcome of the ultraviolet photoelectron spectroscopy (UPS) of BiOI exhibited that the holes from the valence band of BiOI can oxidize the water to accomplish an oxygen evolution.