Water Splitting at the Phase Transition of Ferroelectric Oxide Single Crystals

Ferroelectric surfaces are amazing playgrounds for reduction and oxidation reactions since they permanently accumulate surface charges and fields and show specific electrochemical reactivity as a function of the ferroelectric polarization [1,2,3]. Among surface electrochemical reactions, water splitting is naturally observed on FE oxide surfaces and hence hints at their application not only for water decomposition (i.e. H2 production) but also as new platforms for catalysis. Moreover, the chemical reactivity of the FE surface seems to couple to internal FE polarization via many different mechanisms. This feature opens new opportunities such as ferrocatalysis, that is, to exploit ferroelectric surfaces in catalysis for water splitting since ferroelectric polarization becomes a switch to adjust surface catalytic properties.[4]<br/><br/>Here, I will present a study of the water splitting reactions on ferroelectric surfaces as a function of polarization, obtained from the combination of near ambient pressure XPS analysis and Scanning Probe Microscopy techniques (essentially Piezoresponse Force Microscopy and Kelvin Probe Force Microscopy), and demonstrate the emergence of ferrocatalysis, upon cooling at the paraelectric-ferroelectric phase transition of BaTiO3 single crystals. I’ll show how the surface redox activity is coupled to ferroelectricity by several different factors: the polarity of the stray electric fields, the coupling to screening mechanisms and the specific chemical active sites of each surface. In this sense, the potential of ferroelectric materials for pyrocatalytic water splitting applications will be discussed.<br/><br/><b>References</b><br/>[1] K. Cordero-Edwards, et al. J. Phys. Chem. C, 120, 24048 (2016).<br/>[2] N. Domingo, et al. Phys. Chem.Chem.Phys, 21 (2019), 4920<br/>[3] N.Domingo, et al., Nanoscale, 11 (2019) 17920<br/>[4] I. Spasojevic, PhD Thesis, Universitat Autonoma de Barcelona, June 2022.