SECM for the study and the screening of photoelectrode architectures

Photoelectrochemical water splitting represents an ideal system for the storage of sunlight energy through the production of H2. While many researchers find and design new promising semiconductors, an important effort is dedicated to the research of materials to be deposited on top of the semiconductors (overlayers) to improve the performance of the resulting photoelectrode architecture. The role of overlayers was initially addressed to their ability of improving interfacial reactions or quenching surface traps[1] . However, further study highlighted their more is likely related to an induced modification of the semiconductor electron density[2] or the ability of storing the photogenerated holes thus decreasing the probability of charge recombination [3,4]. This greatly extends the possible candidates for overlayers and requires new efficient screening methods. In this communication we will show our most recent outcomes obtained using SECM for studying both semiconductors and overlayers. The main part of the work consists in the study and the screening of overlayers deposited onto hematite (α-Fe2O3) photoanodes [5]. This was mainly done in the substrate generation/tip collection mode on arrays of overlayers deposited onto a common semiconductor layer adopting the method recently proposed for screening electrocatalysts for the oxygen evolution [6] that consists in pulsing the substrate potential to achieve a reduced interference between spots while the tip addresses every spot collecting the generated oxygen. [1] K. Sivula, F. Le Formal, M. Grätzel, ChemSusChem, 4 (2011) 423-449 [2] M. Barroso, C.A. Mesa, S.R. Pendlebury, A.J. Cowana, T. Hisatomi, K. Sivula, M. Grätzel, D.R. Klug, J.R. Durrant PNAS, 109 (2012) 15640–15645 [3] L. Badia-Bou, E. Mas-Marza, Rodenas P., E. M. Barea, F. Fabregat-Santiago, S. Gimenez, E. Peris, J. Bisquert, J. Phys. Chem. C, 117 (2013) 3826−3833 [4] F. Lin, S.W. Boettcher, Nature Materials, 13 (2014) 81-86 [5] M. Marelli, A. Naldoni, A. Minguzzi, M. Allieta, T. Virgili, G. Scavia, S. Recchia, R. Psaro, V. Dal Santo, ACS Appl. Mater. Interfaces, 6 (2014) 11997-12004. [6] A. Minguzzi, D. Battistel, J. Rodriguez-Lopez, A. Vertova, S. Rondinini, A.J. Bard, S. Daniele, J. Phys. Chem. C, 119 (2015) 2941–2947