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 O₂ evolution. However, the cocatalyst for O₂ evolution has been less investigated, and few effective cocatalysts were reported. This paper reports that the O₂ 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 O₂ evolution from photocatalytic water oxidation. By depositing the CoPi as the oxidation cocatalyst and Pt as the reduction cocatalyst on an yttrium-doped BiVO₄ (Bi_0.5Y_0.5VO₄), overall water splitting reaction to H₂ and O₂ was realized. Our work also reveals the essential relations between photocatalysis and electrocatalysis in water splitting reaction