Volume 2, Issue 5, Pages 668-675 (May 2017) The Role of Ru Redox in pH-Dependent Oxygen Evolution on Rutile Ruthenium Dioxide Surfaces  Kelsey A. Stoerzinger, Reshma R. Rao, Xiao Renshaw Wang, Wesley T. Hong, Christopher M. Rouleau, Yang Shao-Horn  Chem  Volume 2, Issue 5, Pages 668-675 (May 2017) DOI: 10.1016/j.chempr.2017.04.001 Copyright © 2017 Elsevier Inc. Terms and Conditions

Chem 2017 2, 668-675DOI: (10.1016/j.chempr.2017.04.001) Copyright © 2017 Elsevier Inc. Terms and Conditions

Figure 1 Current Density from RuO2 with Noted Orientation in Ar-Saturated 0.1 M KOH at 50 mV/s Shown are (101), (001), and (111) RuO2 grown on TiO2, (100) grown on SrTiO3, and (110) grown on MgO. Schematics of the surface for each orientation are shown to the right of the cyclic voltammetry sweeps. Current densities are offset for clarity. Chem 2017 2, 668-675DOI: (10.1016/j.chempr.2017.04.001) Copyright © 2017 Elsevier Inc. Terms and Conditions

Figure 2 pH Dependence of the Ru Redox at ∼1.35 V and OER Current (A and B) CV measurements at 50 mV/s in Ar-saturated KOH for the (100) surface (A) and the (101) surface (B). (C) The pH dependence (reaction order) for OER activity on the RHE scale was measured by CV (solid) and potentiostatic (open) measurements (Figure S8). The super-Nernstian shift of the redox peak at ∼1.35 V on the RHE scale is shown for comparison. (D and E) Position of Ru redox (left, circle) and OER current at 1.51 V on the RHE scale (right, triangle) and the pH used for determining the reaction order and super-Nernstian shift, which are negligible for the (100) surface (D) and notable for the (101) surface (E). Chem 2017 2, 668-675DOI: (10.1016/j.chempr.2017.04.001) Copyright © 2017 Elsevier Inc. Terms and Conditions

Figure 3 OER Activity of Distinct RuO2 Facets (A) Tafel plot from potentiostatic measurements (constant applied voltage, points) shows V-iR versus |i| on a logarithmic scale. Solid lines correspond to CVs of the tenth OER cycle that preceded potentiostatic measurements, averaging forward and reverse sweeps. (B) OER activity, given as the current density at 1.53 V versus RHE (0.3 V overpotential), scales with the charge of the redox peak at ∼1.35 V versus RHE, which was distinct from the OER catalytic wave. Chem 2017 2, 668-675DOI: (10.1016/j.chempr.2017.04.001) Copyright © 2017 Elsevier Inc. Terms and Conditions