Tuning the Electronic Spin State of Catalysts by Strain Control for Highly Efficient Water Electrolysis

• Published in: Small methods 2018-05, Vol.2 (5), p.n/a
• Main Authors: Hsu, Shao‐Hui, Hung, Sung‐Fu, Wang, Hsin‐Yi, Xiao, Fang‐Xing, Zhang, Liping, Yang, Hongbin, Chen, Hao Ming, Lee, Jong‐Min, Liu, Bin
• Format: Article
• Language: English
• Subjects: adsorption; oxygen Evolution; spin State; spinel; strain
• ISSN: 2366-9608; 2366-9608
• DOI: 10.1002/smtd.201800001

The electronic configuration is crucial in governing the binding strength of intermediates with catalysts, yet it is still challenging to control the catalysts' surface electronic spin state. Here, it is demonstrated that through surface metal–organic framework transformation followed by acid etching, the electronic spin state of surface Co3+ ions on spinel Co3O4 can be transformed from t2g6 to the high electronic spin state of t2g4eg2 by expanding the surface lattice constant, which significantly enhances the overlap of the eg orbital of cobalt with the oxygen adsorbates, and greatly improves the intermediates adsorption and thus the oxygen evolution reaction activity. The high electronic spin rich Co3O4 electrode exhibits an anodic current density of 10 mA cm−2 at an overpotential of 280 mV. The finding offers a rational design strategy to manipulate the electronic spin state of catalyst and the hybridization of molecular orbitals in water electrolysis. Low‐spin Co3+ (t2g6) on spinel Co3O4 can be transformed to high‐spin Co3+ (t2g4eg2) via expanding the lattice of Co3O4 nanowires on the surface, which greatly enhances the overlap of the eg orbital of cobalt with the oxygen adsorbates, and thus facilitates the electrocatalytic activity of the oxygen evolution reaction.