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CoPi/BiVO 4 Photocatalyst CATHERINE BRIDGES AND CONNOR HAYES

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CoPi/BiVO 4 & Water Oxidation Bismuth Vanadate (BiVO 4 ) Monoclinic scheelite BiVO 4 Photocatalytic Water Oxidation Cobalt Phosphate Cocatalyst Addition of CoPi increased activity by 7x Applications O 2 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, 1900-1909.

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PEC Cell Water Oxidation 3 electrode system Xenon Lamp excites the photocatalyst Formation of O 2 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 BiVO 4 electrodes. Phys. Chem. Chem. Phys. 2011, 13, 21392-21401. Wang, D; Li, R; Zhu, J; Shi, J; Han, J; Zong, X; Li, C. Photocatalytic Water Oxidation on BiVO 4 with the Electrocatalyst as an Oxidation CoCatalyst: Essential Relations between Electrocatalyst and Photocatalyst. J. Phys. Chem. 2012, 116, 5082-5089.

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Preparation of CoPi/BiVO 4 1. Synthesis of BiVO 4 : 1:1 stoichiometric mixture of Bi(NO 3 ) 3 and NH 4 VO 3 2. Coating onto FTO working electrode 3. Formation and deposition of CoPi: 0.1M K 3 PO 4 and 0.5mM CoCl 2 FTO Electrode BiVO 4 CoPi Deposition Jeon, T.; Choi, W.; Park, H.; Cobalt-phosphate complexes catalyze the photoelectrochemical water oxidation of BiVO 4 electrodes. Phys. Chem. Chem. Phys. 2011, 13, 21392-21401.

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Structure of Photocatalyst Monoclinic Scheelite BiVO 4 Photocatalytic Molecular Cobaltate Clustered (MCC) CoPi Allows for Co IV 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, 13692-13701. Suarez, C; Hernadez, S; Russo, N. BiVO 4 as photocatalyst for solar fuels through water splitting: A Short Review. Appl. Catal. A: Gen. 2014, 1-13.

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Mechanism of CoPi/BiVO 4 Light excites an electron in BiVO 4 CoPi donates its electron to BiVO 4 Cobalt centers 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, 13692-13701. 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, 18370-18377.

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XPS Spectra w/o CoPi = Bare BiVO 4 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 BiVO 4 electrodes. Phys. Chem. 2011, 13, 21392-21401.

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SEM images of Bare BiVO 4 and CoPi/BiVO 4 Bare BiVO 4 CoPi on BiVO 4 Wang, D.; Li, R.; Zhu, J.; Shi, J.; Han, J.; Zong, X.; Li, C. Photocatalytic Water Oxidation on BiVO 4 with the Electrocatalyst as an Oxidation Cocatalyst: Essential Relations between Electrocatalyst and Photocatalyst. J. Phys. Chem. 2012, 116, 5082-5089.

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O 2 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 BiVO 4 with the Electrocatalyst as an Oxidation Cocatalyst: Essential Relations between Electrocatalyst and Photocatalyst. J. Phys. Chem. 2012, 116, 5082-5089.

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Comparison with other Cocatalysts CoPi is da best 1 23 4 5 6 Wang, D.; Li, R.; Zhu, J.; Shi, J.; Han, J.; Zong, X.; Li, C. Photocatalytic Water Oxidation on BiVO 4 with the Electrocatalyst as an Oxidation Cocatalyst: Essential Relations between Electrocatalyst and Photocatalyst. J. Phys. Chem. 2012, 116, 5082-5089.

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Summary The addition of the cocatalyst CoPi exponentially enhances the water oxidizing ability of the photocatalyst BiVO 4. 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.

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