Title: Spectroscopic Verification of Adsorbed Hydroxyl Intermediate in the Bifunctional Mechanism of Hydrogen Oxidation Reaction

Authors: Yao-Hui Wang, Xiao-Ting Wang, Huajie Ze, Xia-Guang Zhang, Petar M. Radjenovic, Yue-Jiao Zhang Jin-Chao Dong, Zhong-Qun Tian, Jian-Feng Li

Abstract: Elucidating hydrogen oxidation reaction (HOR) mechanisms in alkaline conditions is vital for understanding and improving the efficiency of anion‐exchange membrane fuel cells (AEMFCs). However, uncertainty remains around the alkaline HOR mechanism due to a lack of direct  in situ  evidence of the reaction intermediates. Herein,  in situ  electrochemical surface‐enhanced Raman spectroscopy (SERS) and density functional theory (DFT) calculations were used to study HOR processes on both PtNi alloy and pure Pt surfaces. Spectroscopic evidence indicates that adsorbed hydroxyl species (OH  ad  ) were directly involved in HOR processes in alkaline conditions on the PtNi alloy surface. However, OH  ad  species were not observed on the surface of pure Pt during the HOR. We show that Ni doping promoted hydroxyl adsorption on the Pt‐alloy catalytic surface, improving the HOR activity. DFT calculations also suggest that the free energy was decreased by hydroxyl adsorption. Thus, we provide direct evidence of the presence of the OH  ad  intermediate species on an oxophilic metal surface during the HOR and deduce its important role in improving the HOR activity and rate. Consequently, tuning OH adsorption by designing bifunctional catalysts is an efficient method for promoting HOR activity.

Full-Link: https://onlinelibrary.wiley.com/doi/10.1002/anie.202015571