An essential descriptor for the oxygen evolution reaction on reducible metal oxide surfaces† †Electronic supplementary information (ESI) available: Computational methods. See DOI: 10.1039/c8sc04521f

The number of excess electrons (NEE), as a descriptor, perfectly reproduces the OER volcano curve of TiO2(110) plotted using ΔGO – ΔGOH.

[1]  Venkatasubramanian Viswanathan,et al.  Universality in Oxygen Reduction Electrocatalysis on Metal Surfaces , 2012 .

[2]  J. Nørskov,et al.  Oxygen vacancies as active sites for water dissociation on rutile TiO(2)(110). , 2001, Physical review letters.

[3]  G. Pacchioni,et al.  Increasing Oxide Reducibility: The Role of Metal/Oxide Interfaces in the Formation of Oxygen Vacancies , 2017 .

[4]  Tejs Vegge,et al.  Functional Independent Scaling Relation for ORR/OER Catalysts , 2016 .

[5]  Reshma R. Rao,et al.  Towards identifying the active sites on RuO2(110) in catalyzing oxygen evolution , 2017 .

[6]  T. Frauenheim,et al.  Oxygen deficiency in Ti O 2 : Similarities and differences between the Ti self-interstitial and the O vacancy in bulk rutile and anatase , 2015 .

[7]  A. Fisher,et al.  Electron traps and their effect on the surface chemistry of TiO2(110) , 2010, Proceedings of the National Academy of Sciences.

[8]  C. Peden,et al.  Insights into Photoexcited Electron Scavenging Processes on TiO2 Obtained from Studies of the Reaction of O2 with OH Groups Adsorbed at Electronic Defects on TiO2 (110) , 2003 .

[9]  Colin F. Dickens,et al.  A Theoretical Investigation into the Role of Surface Defects for Oxygen Evolution on RuO2 , 2017 .

[10]  John Kitchin,et al.  Universality in Oxygen Evolution Electrocatalysis on Oxide Surfaces , 2011 .

[11]  R. Rousseau,et al.  Impact of Nonadiabatic Charge Transfer on the Rate of Redox Chemistry of Carbon Oxides on Rutile TiO2(110) Surface , 2015 .

[12]  Yafei Li,et al.  PtTe Monolayer: Two-Dimensional Electrocatalyst with High Basal Plane Activity toward Oxygen Reduction Reaction. , 2018, Journal of the American Chemical Society.

[13]  B. Hammer,et al.  The Role of Interstitial Sites in the Ti3d Defect State in the Band Gap of Titania , 2008, Science.

[14]  N. A. Deskins,et al.  Anticorrelation between surface and subsurface point defects and the impact on the redox chemistry of TiO2(110). , 2015, Chemphyschem : a European journal of chemical physics and physical chemistry.

[15]  Ioannis Katsounaros,et al.  Oxygen electrochemistry as a cornerstone for sustainable energy conversion. , 2014, Angewandte Chemie.

[16]  I. Lyubinetsky,et al.  Ability of Ti O 2 ( 110 ) surface to be fully hydroxylated and fully reduced , 2015 .

[17]  Colin F. Dickens,et al.  Combining theory and experiment in electrocatalysis: Insights into materials design , 2017, Science.

[18]  R. P. Gupta,et al.  Oxide Materials for Development of Integrated Gas Sensors—A Comprehensive Review , 2004 .

[19]  J. Nowotny,et al.  Defect disorder of titanium dioxide. , 2006, The journal of physical chemistry. B.

[20]  J. Nørskov,et al.  Electrolysis of water on oxide surfaces , 2007 .

[21]  J. Nørskov,et al.  Improved adsorption energetics within density-functional theory using revised Perdew-Burke-Ernzerhof functionals , 1999 .

[22]  G. Kresse,et al.  Efficiency of ab-initio total energy calculations for metals and semiconductors using a plane-wave basis set , 1996 .

[23]  Roy E. Welsch,et al.  Descriptors of Oxygen-Evolution Activity for Oxides: A Statistical Evaluation , 2016 .

[24]  G. Thornton,et al.  Oxygen vacancy origin of the surface band-gap state of TiO2(110). , 2010, Physical review letters.

[25]  E. Sato,et al.  Oxygen Evolution on La1 − x Sr x Fe1 − y Co y O 3 Series Oxides , 1980 .

[26]  Michel Dupuis,et al.  Localized Electronic States from Surface Hydroxyls and Polarons in TiO2(110) , 2009 .

[27]  D. Cao,et al.  A universal principle for a rational design of single-atom electrocatalysts , 2018, Nature Catalysis.

[28]  S. Trasatti.  Electrocatalysis by oxides — Attempt at a unifying approach , 1980 .

[29]  Burke,et al.  Generalized Gradient Approximation Made Simple. , 1996, Physical review letters.

[30]  J. Goodenough,et al.  A Perovskite Oxide Optimized for Oxygen Evolution Catalysis from Molecular Orbital Principles , 2011, Science.

[31]  S. Tong,et al.  Interaction of O2 with reduced rutile TiO2(110) surface , 2013 .

[32]  C. Minot,et al.  Scaling reducibility of metal oxides , 2017, Theoretical Chemistry Accounts.

[33]  Irving Langmuir,et al.  THE ARRANGEMENT OF ELECTRONS IN ATOMS AND MOLECULES. , 1919 .

[34]  Bin Xu,et al.  Intrinsic Role of Excess Electrons in Surface Reactions on Rutile TiO2 (110): Using Water and Oxygen as Probes , 2018 .

[35]  B. Liu,et al.  Identification of Surface Reactivity Descriptor for Transition Metal Oxides in Oxygen Evolution Reaction. , 2016, Journal of the American Chemical Society.

[36]  J. Nørskov,et al.  Oxidation and Photo-Oxidation of Water on TiO2 Surface , 2008 .

[37]  K. Burke,et al.  Rationale for mixing exact exchange with density functional approximations , 1996 .

[38]  Venkatasubramanian Viswanathan,et al.  Importance of Correlation in Determining Electrocatalytic Oxygen Evolution Activity on Cobalt Oxides , 2012 .

[39]  S. Trasatti.  Electrocatalysis in the anodic evolution of oxygen and chlorine , 1984 .

[40]  U. Diebold,et al.  Following the Reduction of Oxygen on TiO2 Anatase (101) Step by Step. , 2016, Journal of the American Chemical Society.

[41]  G. Kresse,et al.  From ultrasoft pseudopotentials to the projector augmented-wave method , 1999 .

[42]  J. Rossmeisl,et al.  Physical and chemical nature of the scaling relations between adsorption energies of atoms on metal surfaces. , 2012, Physical review letters.

[43]  Joseph H. Montoya,et al.  Trends in adsorption of electrocatalytic water splitting intermediates on cubic ABO3 oxides. , 2018, Physical chemistry chemical physics : PCCP.

[44]  Annabella Selloni,et al.  Electronic structure of defect states in hydroxylated and reduced rutile TiO2(110) surfaces. , 2006, Physical review letters.

[45]  Xue-qing Gong,et al.  CO Oxidation at Rutile TiO2(110): Role of Oxygen Vacancies and Titanium Interstitials , 2015 .

[46]  A. Selloni,et al.  Adsorption and reactions of O2 on anatase TiO2. , 2014, Accounts of chemical research.

[47]  N. A. Deskins,et al.  Defining the Role of Excess Electrons in the Surface Chemistry of TiO2 , 2010 .

[48]  H. Jónsson,et al.  Origin of the Overpotential for Oxygen Reduction at a Fuel-Cell Cathode. , 2004, The journal of physical chemistry. B.

[49]  J. Nørskov,et al.  Electrolysis of water on (oxidized) metal surfaces , 2005 .

[50]  F. Calle‐Vallejo,et al.  A New Type of Scaling Relations to Assess the Accuracy of Computational Predictions of Catalytic Activities Applied to the Oxygen Evolution Reaction , 2017 .

[51]  Marc T. M. Koper,et al.  Thermodynamic theory of multi-electron transfer reactions: Implications for electrocatalysis , 2011 .

[52]  Kresse,et al.  Efficient iterative schemes for ab initio total-energy calculations using a plane-wave basis set. , 1996, Physical review. B, Condensed matter.