1. CoPi/BiVO4 Photocatalyst
Catherine Bridges and Connor Hayes

2. CoPi/BiVO4 & Water Oxidation
Bismuth Vanadate (BiVO4)
Monoclinic scheelite BiVO4
Photocatalytic Water Oxidation
Cobalt Phosphate Cocatalyst
Addition of CoPi increased activity by 7x
Applications O2
Suarez, C; Hernadez, S; Russo, N. BiVO4 as photocatalyst for solar fuels through water splitting: A Short Review. Appl. Catal. A: Gen. 2014, 1-13.
Yang, J; Wang, D; Han, H; Li, C. Roles of Cocatalysts in Photocatalysis and Photoelectrocatalysis. Acc. Chem. Res. 2013, 46,

3. PEC Cell Water Oxidation
3 electrode system
Xenon Lamp excites the photocatalyst
Formation of O2 and photoanodic current occurred
H+ reduction occurs at the counter electrode
Jeon, T.; Choi, W.; Park, H.; Cobalt-phosphate complexes catalyze the photoelectrochemical water oxidation of BiVO4 electrodes. Phys. Chem. Chem. Phys. 2011, 13,
Wang, D; Li, R; Zhu, J; Shi, J; Han, J; Zong, X; Li, C. Photocatalytic Water Oxidation on BiVO4 with the Electrocatalyst as an Oxidation CoCatalyst: Essential Relations between Electrocatalyst and Photocatalyst. J. Phys. Chem. 2012, 116,

4. Preparation of CoPi/BiVO4
𝐵𝑖(𝑁 𝑂 3 ) 3 +𝑁 𝐻 4 𝑉 𝑂 3 →𝑩𝒊𝑽 𝑶 𝟒
Synthesis of BiVO4: 1:1 stoichiometric mixture of Bi(NO3)3 and NH4VO3
Coating onto FTO working electrode
Formation and deposition of CoPi: 0.1M K3PO4 and 0.5mM CoCl2
CoPi Deposition
BiVO4
FTO Electrode
Jeon, T.; Choi, W.; Park, H.; Cobalt-phosphate complexes catalyze the photoelectrochemical water oxidation of BiVO4 electrodes. Phys. Chem. Chem. Phys. 2011, 13,

5. Structure of Photocatalyst
Monoclinic Scheelite BiVO4
Photocatalytic
Molecular Cobaltate Clustered (MCC) CoPi
Allows for CoIV oxidation state
Kanan, M; Yano, J; Surendranath, Y; Dinca, M; Yachandra, V; Nocera, D. Structure and Valency of a Cobalt-Phosphate Water Oxidation Catalyst Determined by in Situ X-Ray Spectroscopy. J. Am. Chem. Soc., 2010, 132,
Suarez, C; Hernadez, S; Russo, N. BiVO4 as photocatalyst for solar fuels through water splitting: A Short Review. Appl. Catal. A: Gen. 2014, 1-13.

6. Mechanism of CoPi/BiVO4
Light excites an electron in BiVO4
CoPi donates its electron to BiVO4
Cobalt center’s oxidation state increases
Process continues until Co(IV) is achieved
Water oxidation occurs
Kanan, M; Yano, J; Surendranath, Y; Dinca, M; Yachandra, V; Nocera, D. Structure and Valency of a Cobalt-Phosphate Water Oxidation Catalyst Determined by in Situ X-Ray Spectroscopy. J. Am. Chem. Soc., 2010, 132,
Zhong, D; Sujung, C; Gamelin, D. Near Complete Supression of Surface Recombination in Solar Photoelectrolysis by “Co-Pi” Catalyst-Modified W:BiVO4. J. Am. Chem. Soc. 2011, 133,

7. XPS Spectra w/o CoPi = Bare BiVO4 S-ED = step wise electrodeposition
S-PD = stepwise photodeposition
S-ED (L) = stepwise electrodeposition after 12 hours
S-ED on FTO = Bare CoPi
Co peaks
P peaks
Jeon, T.; Choi, W.; Park, H. Cobalt-phosphate complexes catalyze the photoelectrochemical water oxidation of BiVO4 electrodes. Phys. Chem. 2011, 13,

8. SEM images of Bare BiVO4 and CoPi/BiVO4
CoPi on BiVO4
Wang, D.; Li, R.; Zhu, J.; Shi, J.; Han, J.; Zong, X.; Li, C. Photocatalytic Water Oxidation on BiVO4 with the Electrocatalyst
as an Oxidation Cocatalyst: Essential Relations between Electrocatalyst and Photocatalyst. J. Phys. Chem. 2012, 116,

9. O2 Evolution Capability
Optimal CoPi Loading = 1.0% wt
Wang, D.; Li, R.; Zhu, J.; Shi, J.; Han, J.; Zong, X.; Li, C. Photocatalytic Water Oxidation on BiVO4 with the Electrocatalyst as an Oxidation Cocatalyst: Essential Relations between Electrocatalyst and Photocatalyst. J. Phys. Chem. 2012, 116,

10. Comparison with other Cocatalysts1 2 3
CoPi is da best 4 5 6
Wang, D.; Li, R.; Zhu, J.; Shi, J.; Han, J.; Zong, X.; Li, C. Photocatalytic Water Oxidation on BiVO4 with the Electrocatalyst as an Oxidation Cocatalyst: Essential Relations between Electrocatalyst and Photocatalyst. J. Phys. Chem. 2012, 116,

11. Summary
The addition of the cocatalyst CoPi exponentially enhances the water oxidizing ability of the photocatalyst BiVO4.
This combination is preferred because of its low toxicity, efficiency and availability (aka cheap).
Coupling of this photocatalyst with a high yielding hydrogen evolver could potentially give the most efficient water splitting system.