RuO2 is commercially employed as an anodic catalyst in the chlor-alkali process. It is also one of the most active electrocatalysts for the oxidation of water, relevant to electrochemical water splitting. However, the use of RuO2 is limited by its low anodic stability under acidic conditions, especially at high overpotentials. In the present work, the electrochemical stability of model RuO2(110)/Ru(0001) anodes was investigated in order to gain a deeper understanding of the relation between structure and performance in Cl2 and O2 evolution reactions (CER and OER, respectively). Online electrochemical mass spectrometry was used to determine the onset potential of CER and OER in HCl and H2SO4 electrolytes, respectively. The onset potential of OER was higher in HCl than in H2SO4 due to competition with the kinetically more favorable CER. A detailed stability evaluation revealed pitting corrosion of the electrode surface with exposure of Ru(0001) metal substrate concomitant with the formation of a hydrous RuO2 in some areas regardless of the applied electrochemical treatment. However, despite local pitting, the RuO2(110) layer preserves its thickness in most areas. Degradation of the electrode was found to be less severe in 0.5 M HCl due to a decrease in the faradaic efficiency of RuO2 oxidation caused by competition with the kinetically more favorable CER.
|Original language||English (US)|
|State||Published - 2020|
Bibliographical noteKAUST Repository Item: Exported on 2021-07-13
Acknowledgements: The authors thank ESRF for technical and financial support during beam time IHCH-1283 at beamline ID03. Dr. Iman Sohrabnejad-Eskan of JLU Giessen and Dr. Johannes Pfrommer of DESY Hamburg are acknowledged for technical support and fruitful discussions. The authors would like to thank the following colleagues of Eindhoven University of Technology: Ad H. Wonders for useful discussions and assistance with the OLEMS measurements; Adelheid M. Elemans-Mehring for ICP-OES measurements; Alexey Bolshakov for assistance on synchrotron measurements. A.G. and E.J.M.H. acknowledge funding by the Dutch Research School Combination Catalysis Controlled by Chemical Design (NRSC-Catalysis) and an NWO Vici grant. M.E.C.P. acknowledges funding by a Graduate School program from the Netherlands Organization for Scientific Research (NWO). H.O. thanks BMBF (project: 05K2016-HEXCHEM) and DFG (Ov21-16 within SPP2080) for financial support.