Structural Changes in RuO2 during Electrochemical Hydrogen Evolution

A comprehensive theoretical study of the X-ray photoelectron shifts for RuO2 during hydrogen evolution has been performed. The shifts have been calculated using first-principles density functional theory and are compared with previous theoretical and experimental results to reconsider the proposed structural changes occurring during hydrogen evolution on RuO2. We find that during hydrogen evolution hydrogen enters the rutile RuO2 lattice and converts oxygen groups into hydroxyl groups and that this process explains the experimentally observed increase in unit cell dimensions as well as observed chemical shifts. Furthermore, carbon contamination is the most likely explanation for a set of peaks previously identified as caused by a new RuO(OH)2 phase. We find that formation of metallic Ru is just one possible explanation for another peak in the X-ray photoelectron spectrum and that explanations including conversion of RuO2 into Ru(OH)3, or removal of oxygen from Ru active surface sites, also can explain the observed shifts.