Electrodeposited Co-Pi Catalyst on α-Fe2O3 Photoanode for Water-Splitting Applications


Material Science and Engineering Department, K. N. Toosi University of Technology, Tehran, Iran


Optoelectronic properties of hematite (α-Fe2O3) as a photoanode and the required over-potential in photo-assisted water splitting has been improved by presence of Co-Pi on its surface. In order to increase the lifetime of the photogenerated holes and lower the applied bias, cobalt-phosphate (Co-Pi) on nanostructured α-Fe2O3 by electrodeposition was deposited. The nanostructure morphology of the α-Fe2O3 was confirmed by XRD and SEM. After depositing four different thicknesses of Co-Pi on α-Fe2O3, their photo-electrochemical (PEC) property was determined using linear sweep voltammetry (LSV) and chronoamperometry. The SEM and EDX results showed a complete coverage of Co-Pi on α-Fe2O3 and that the Co:P ratio was approximately 1:1.9 for the best produced catalyst. The highest performance of about 200 mV decrease in the onset potential was achieved for the 30-minutes electrodeposited sample. The Co-Pi/α-Fe2O3 catalyst showed an enhancement of 100% of photocurrent compared to the bare α-Fe2O3.


1.     Fujishima, A., and Honda, K., “Electrochemical Photolysis of Water at a Semiconductor Electrode”, Nature,  Vol. 238, No. 5358, (1972), 37–38.
2.     Zhong, D.K., and Gamelin, D.R., “Photoelectrochemical Water Oxidation by Cobalt Catalyst (‘Co−Pi’)/α-Fe2O3 Composite Photoanodes: Oxygen Evolution and Resolution of a Kinetic Bottleneck”, Journal of the American Chemical Society,  Vol. 132, No. 12, (2010), 4202–4207.
3.     Shinar, R., and Kennedy, J.H., “Photoactivity of doped α-Fe2O3 electrodes”, Solar Energy Materials,  Vol. 6, No. 3, (1982), 323–335.
4.     Zhong, D., Cornuz, M., Sivula, K., Grätzel, M., and Gamelin. D.R, “Photo-assisted electrodeposition of cobalt–phosphate (Co–Pi) catalyst on hematite photoanodes for solar water oxidation”, Energy & Environmental Science,  Vol. 4, No. 5, (2011), 1759–1764.
5      Kay, A., Cesar, I., and Grätzel, M., “New benchmark for water photooxidation by nanostructured α-Fe2O3 films”, Journal of the American Chemical Society,  Vol. 128, No. 49, (2006), 15714–15721.
6.     McDonald, K.J., and Choi, K.-S., “Photodeposition of Co-Based Oxygen Evolution Catalysts on α-Fe2O3 Photoanodes”, Chemistry of Materials,  Vol. 23, No. 7, (2011), 1686–1693.
7.     Carroll, G.M., Zhong, D.K., and Gamelin, D.R., “Mechanistic insights into solar water oxidation by cobalt-phosphate-modified α-Fe2O3 photoanodes”, Energy & Environmental Science,  Vol. 8, No. 2, (2015), 577–584.
8.     Van de Krol, R., and Grätzel, M., Photoelectrochemical Hydrogen Production, Electronic Materials: Science & Technology;  Vol. 102, Springer, (2012).
9.     Barroso, M., Cowan, A.J., Pendlebury, S.R., Grätzel, M., Klug, D.R., and Durrant, J.R., “The Role of Cobalt Phosphate in Enhancing the Photocatalytic Activity of α-Fe2O3 toward Water Oxidation”, Journal of the American Chemical Society,  Vol. 133, No. 38, (2011), 14868–14871.
10.   Barroso, M., Mesa, C.A., Pendlebury, S.R., owan, A.J., Hisatomi, T., Sivula, K., Grätzel, M., Klug, D.R., and Durrant, J.R., “Dynamics of photogenerated holes in surface modified α-Fe2O3 photoanodes for solar water splitting”, Proceedings of the National Academy of Sciences of the United States of America,  Vol. 109, No. 39, (2012), 15640–15645.
11.   Lin, F., and Boettcher, S.W., “Adaptive semiconductor/ electrocatalyst junctions in water-splitting photoanodes”, Nature Materials,  Vol. 13, No. 1, (2014), 81–86.
12.   Schrebler, R., Bello, K., Vera, F., Cury, P., Muñoz, E., del Río, R., Meier, H.G., Córdova, R., and Dalchiele, E.A., “An electrochemical deposition route for obtaining α-Fe2O3 thin films”, Electrochemical and solid-state letters,  Vol. 9, No. 7, (2006), C110–C113.
13.   Kanan, M.W., and Nocera, D.G., “In Situ Formation of an Oxygen-Evolving Catalyst in Neutral Water Containing Phosphate and Co2+”, Science,  Vol. 321, No. 5892, (2008), 1072–1075.
14.   Chirita M, Grozescu I, Taubert L, Radulescu H, Princz E, Stefanovits-Bányai É, Caramalau C, Bulgariu L, Macoveanu M, Muntean, C., “Fe2O3–nanoparticles, physical properties and their photochemical and photoelectrochemical applications”, Chemical Bulletin of “POLITEHNICA” University of Timisoara,  Vol. 54, No. 68, (2009), 1–8.
15.   Enache, C.S., Liang, Y.Q., and Van de Krol, R., “Characterization of structured α-Fe2O3 photoanodes prepared via electrodeposition and thermal oxidation of iron”, Thin Solid Films,  Vol. 520, No. 3, (2011), 1034–1040.
16.   Bak, A., Choi, W., and Park, H., “Enhancing the photoelectrochemical performance of hematite (α-Fe2O3) electrodes by cadmium incorporation”, Applied Catalysis B: Environmental,  Vol. 110, (2011), 207–215.
17.   Shi, X., Zhang, K., and Park, J.H., “Understanding the positive effects of (Co–Pi) co-catalyst modification in inverse-opal structured α-Fe2O3-based photoelectrochemical cells”, International Journal of Hydrogen Energy,  Vol. 38, No. 29, (2013), 12725–12732.
18.   Surendranath, Y., Kanan, M.W., and Nocera, D.G., “Mechanistic Studies of the Oxygen Evolution Reaction by a Cobalt-Phosphate Catalyst at Neutral pH”, Journal of the American Chemical Society,  Vol. 132, No. 46, (2010), 16501–16509.
19.   Lutterman, D.A., Surendranath, Y., and Nocera, D.G., “A Self-Healing Oxygen-Evolving Catalyst”, Journal of the American Chemical Society,  Vol. 131, No. 11, (2009), 3838–3839.
20.   Surendranath, Y., Dincǎ, M., and Nocera, D.G., “Electrolyte-Dependent Electrosynthesis and Activity of Cobalt-Based Water Oxidation Catalysts”, Journal of the American Chemical Society,  Vol. 131, No. 7, (2009), 2615–2620.
21.   Steinmiller, E.M.P., and Choi, K.-S., “Photochemical deposition of cobalt-based oxygen evolving catalyst on a semiconductor photoanode for solar oxygen production.”, Proceedings of the National Academy of Sciences of the United States of America,  Vol. 106, No. 49, (2009), 20633–20636.
22.   Liang, Y., Enache, C.S., and Van de Krol, R., “Photoelectrochemical Characterization of Sprayed α-Fe2O3 Thin Films: Influence of Si Doping and SnO2 Interfacial Layer”, International Journal of Photoenergy,  Vol. 2008, (2008), 1–7.
23.   Smith, R.D.L., Prévot, M.S., Fagan, R.D., Zhang, Z., Sedach, P.A., Siu, M.K.J., Trudel, S., and Berlinguette, C.P., “Photochemical route for accessing amorphous metal oxide materials for water oxidation catalysis”, Science,  Vol. 340, No. 6128, (2013), 60–63.
24.   Hahn, N.T., Ye, H., Flaherty, D.W., Bard, A.J., and Mullins, C.B., “Reactive Ballistic Deposition of α-Fe2O3 Thin Films for Photoelectrochemical Water Oxidation”, ACS Nano,  Vol. 4, No. 4, (2010), 1977–1986.
25.   Kanan, M.W., Surendranath, Y., and Nocera, D.G., “Cobalt–phosphate oxygen-evolving compound”, Chemical Society Reviews,  Vol. 38, No. 1, (2009), 109–114.
26.   Bak, T., Nowotny, J., Rekas, M., and Sorrell, C.C., “Photo-electrochemical hydrogen generation from water using solar energy. Materials-related aspects”, International Journal of Hydrogen Energy,  Vol. 27, No. 10, (2002), 991–1022.