Lattice oxygen activation enabled by high-valence metal sites for enhanced water oxidation
Authors: Bocheng Qiu
Xiaobin Feng
Ning Zhang
Ran Long
Dewei Rao
Lejuan Cai
Yang Lu
Yang Chai
Yujie Xiong
Xi Deng
Journal: Nature Communications (2020)
Discipline: Multidisciplinary
Keywords: Anodic oxygen evolution reaction; Transition metal sites; Ni4+ species; Surface reconstructed (oxy)hydroxides; FeCoCrNi alloy film
Affiliations: Department of Applied Physics, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong, P. R. China., The Hong Kong Polytechnic University Shenzhen Research Institute, 518057, Shenzhen, P. R. China., Department of Mechanical Engineering, City University of Hong Kong, Kowloon, Hong Kong, P. R. China., Nano-Manufacturing Laboratory (NML), Shenzhen Research Institute of City University of Hong Kong, 518057, Shenzhen, P. R. China., School of Materials Science and Engineering, Jiangsu University, 212013, Zhenjiang, Jiangsu, P. R. China., Hefei National Laboratory for Physical Sciences at the Microscale, iChEM (Collaborative Innovation Center of Chemistry for Energy Materials), School of Chemistry and Materials Science, National Synchrotron Radiation Laboratory, University of Science and Technology of China, 230026, Hefei, Anhui, P. R. China., Department of Mechanical Engineering, City University of Hong Kong, Kowloon, Hong Kong, P. R. China. ., Nano-Manufacturing Laboratory (NML), Shenzhen Research Institute of City University of Hong Kong, 518057, Shenzhen, P. R. China. ., Department of Applied Physics, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong, P. R. China. ., The Hong Kong Polytechnic University Shenzhen Research Institute, 518057, Shenzhen, P. R. China. .

Abstract:  Anodic oxygen evolution reaction (OER) is recognized as kinetic bottleneck in water electrolysis. Transition metal sites with high valence states can accelerate the reaction kinetics to offer highly intrinsic activity, but suffer from thermodynamic formation barrier. Here, we show subtle engineering of highly oxidized Ni4+ species in surface reconstructed (oxy)hydroxides on multicomponent FeCoCrNi alloy film through interatomically electronic interplay. Our spectroscopic investigations with theoretical studies uncover that Fe component enables the formation of Ni4+ species, which is energetically favored by the multistep evolution of Ni2+→Ni3+→Ni4+. The dynamically constructed Ni4+ species drives holes into oxygen ligands to facilitate intramolecular oxygen coupling, triggering lattice oxygen activation to form Fe-Ni dual-sites as ultimate catalytic center with highly intrinsic activity. As a result, the surface reconstructed FeCoCrNi OER catalyst delivers outstanding mass activity and turnover frequency of 3601 A gmetal-1 and 0.483 s-1 at an overpotential of 300 mV in alkaline electrolyte, respectively. 

Retracted: No

PubPeer comments:
 In Supplementary Figure 38, in-situ electrochemical Raman was used to characterize three electrocatalysts, EA-CCN, EA-FCN, and EA-FCCN. As the noise background is relatively high, which makes the peak assignment is not convincible. Especially considering the inclination of background line from low-to-high wavenumber (or reverse), the broad bump definitely cannot be the evidence of Ni4+-(OO)- marked in the following figures. Can the author explain here how to get this conclusion? ![file] , 
 We thank very much for the question. Indeed, the noise background in Supplementary Figure 3 is relatively high. In Raman spectra, the NiOO- active oxygen species is an intrinsically board but weak peak at the region of 900~1150 cm-1. Similar results are also reported in existing literature (e.g., JACS,2015,137,15112; Angew,2019,58,12999; Angew,2019,58,10295; etc). In the high OER potentials, compared to CCN samples with a very flat Raman spectra without signals, we can observe the board Raman signals for other two samples although the background is inclined, especially for FCCN. The signals are more obvious compared to the ones at low potentials. The Raman intensity is sufficiently high to indicate the existence of NiOO- active oxygen species. Nevertheless, considering its intrinsically weak nature, we just considered this data as supplementary evidence in SI file. ,