Engineering the Structural Defects of Spinel Oxide Nanoneedles by Doping of V for a Highly Efficient Oxygen Evolution Reaction.

Rational design of multi-structural defects in the transition-metal oxides is a very alluring and challenging strategy to significantly improve its oxygen evolution reaction (OER) performance. Herein, a simple and promising element doping approach is demonstrated to fabricate a poor-crystalline V-doping CuCoO (V-CuCoO) nanoneedle with rich oxygen vacancies (V), partially amorphous phase, and Co defects on the carbon fiber (CF) (V-CuCoO/CF). The results indicate that the V doping could further weaken the crystallinity of V-CuCoO, providing the thoroughfares for the convenience of electrolyte penetration and the exposure of active sites. Meanwhile, [CoO] octahedron in the V-CuCoO lattice is gravely distorted due to a strong electronic interaction between the doped V and Co atoms, creating more Co active species. With the merits of these multiple structural defects, V-CuCoO/CF exhibits rich active sites, and its intrinsically electrocatalytic activity is significantly enhanced. The optimized V-CuCoO/CF electrocatalyst has a significantly enhanced OER activity with a required low overpotential of ∼204 and ∼246 mV at a current density of 100 and 300 mA cm, respectively, a small Tafel slope of 40.7 mV dec, and excellent stability in an alkaline medium. Furthermore, the results from the projected partial density of states calculation not only demonstrate that the 3-fol-coordinated Co near V bonded with Cu and V sites (Cu-Co-V) exhibits an enhanced electronic transfer activity but also reveal that the doped V could protect the Co sites from the deactivation by intermediates overbinding on the V sites. This work provides new insights into structure engineering of spinel phase copper cobaltite, resulting in significantly boosting electrocatalytic OER activity.