10.1021/jacs.7b05184.s001 Camilo A. Mesa Camilo A. Mesa Andreas Kafizas Andreas Kafizas Laia Francàs Laia Francàs Stephanie R. Pendlebury Stephanie R. Pendlebury Ernest Pastor Ernest Pastor Yimeng Ma Yimeng Ma Florian Le Formal Florian Le Formal Matthew T. Mayer Matthew T. Mayer Michael Grätzel Michael Grätzel James R. Durrant James R. Durrant Kinetics of Photoelectrochemical Oxidation of Methanol on Hematite Photoanodes American Chemical Society 2017 rate law analysis 1 sun irradiation α- Fe 2 O 3 photoanodes metal oxide surfaces anatase TiO 2 photoanodes methanol oxidation Kinetic isotope effect studies α- Fe 2 O 3 photoinduced absorption spectroscopy unity Faradaic efficiency PEC methanol oxidation 2017-07-22 00:00:00 Journal contribution https://acs.figshare.com/articles/journal_contribution/Kinetics_of_Photoelectrochemical_Oxidation_of_Methanol_on_Hematite_Photoanodes/5303590 The kinetics of photoelectrochemical (PEC) oxidation of methanol, as a model organic substrate, on α-Fe<sub>2</sub>O<sub>3</sub> photoanodes are studied using photoinduced absorption spectroscopy and transient photocurrent measurements. Methanol is oxidized on α-Fe<sub>2</sub>O<sub>3</sub> to formaldehyde with near unity Faradaic efficiency. A rate law analysis under quasi-steady-state conditions of PEC methanol oxidation indicates that rate of reaction is second order in the density of surface holes on hematite and independent of the applied potential. Analogous data on anatase TiO<sub>2</sub> photoanodes indicate similar second-order kinetics for methanol oxidation with a second-order rate constant 2 orders of magnitude higher than that on α-Fe<sub>2</sub>O<sub>3</sub>. Kinetic isotope effect studies determine that the rate constant for methanol oxidation on α-Fe<sub>2</sub>O<sub>3</sub> is retarded ∼20-fold by H/D substitution. Employing these data, we propose a mechanism for methanol oxidation under 1 sun irradiation on these metal oxide surfaces and discuss the implications for the efficient PEC methanol oxidation to formaldehyde and concomitant hydrogen evolution.