(Invited) Intermediates in PEC Water Oxidation — How They Come and How They Go

Abstract

Atmospheric oxygen that we live on is the result of a fundamental evolutionary step in photosynthesis which occurred on Earth 2-3 billion years ago [Biello 2009]. The water oxidation in natural photosystem II accounts for 50% of this oxygen. The man-made analog to this natural process is water oxidation in photoelectrochemical cells - one of the most complex processes in physical chemistry. I will showcase how modern x-ray spectroscopy methods have assisted in the understanding of the molecular pro-cesses which occur in natural [Bora 2013, Ralston 2000, Visser 2001] and in man-made "photosystems". A most recent example is the element and orbital specific identification of transient electron holes in iron oxide [Braun 2012], chemical surface intermediates [Bora 2011] and changes in the water molecules in the electrochemical double layer during photoelectrochemical water oxidation [Braun 2016]. I will also demonstrate how the electronic structure evolution is quantitatively paralleled by the electric transport properties of the electrodes during operation. [Biello 2009] Biello D: The Origin of Oxygen in Earth's Atmosphere. In Scientific American 2009. [Bora 2011] Bora DK et al. Journal of Physical Chemistry C 2011, 115:5619-5625. [Bora 2013] Bora DK et al. JOURNAL OF ELECTRON SPECTROSCOPY AND RELATED PHENOMENA 2013, 190:93-105. [Braun 2012] Braun A et al. Journal of Physical Chemistry C 2012, 116:16870-16875. [Braun 2016] Braun A et al. Catalysis Today 2016, 260:72-81. [Ralston 2000] Ralston CY et al. Journal of the American Chemical Society 2000, 122:10553-10560. [Visser 2001] Visser H et al. Journal of the American Chemical Society 2001, 123:7031-7039.