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

Abstract

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 BiVO 4 . The photocurrent density is also greatly enhanced by loading CoPi on BiVO 4 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 BiVO 4 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 BiVO 4 (Bi 0.5 Y 0.5 VO 4 ), 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.