Photocatalytic Water Oxidation on BiVO4 with the Electrocatalyst as an Oxidation Cocatalyst: Essential Relations between Electrocatalyst and Photocatalyst

The oxygen evolution is kinetically the key step in the photocatalytic water splitting. Cocatalysts could lower the activation potential for O-2 evolution. However, the cocatalyst for O-2 evolution has been less investigated, and few effective cocatalysts were reported. This paper reports that the O-2 evolution rate of photocatalytic water splitting under visible light irradiation can be significantly enhanced when the electrocatalyst cobalt phosphate (denoted as CoPi) was deposited on BiVO4. The photocurrent density is also greatly enhanced by loading CoPi on BiVO4 electrode, and this enhancement in performance shows the similar trend between the photocatalytic activity and photocurrent density. We also found that this tendency is true for BiVO4 loaded with a series of different electrocatalysts as the cocatalysts. These results demonstrate that an effective electrocatalyst of water oxidation can be also an effective cocatalyst for O-2 evolution from photocatalytic water oxidation. By depositing the CoPi as the oxidation cocatalyst and Pt as the reduction cocatalyst on an yttrium-doped BiVO4 (Bi0.5Y0.5VO4), overall water splitting reaction to H-2 and O-2 was realized. Our work also reveals the essential relations between photocatalysis and electrocatalysis in water splitting reaction.