Disordered CoFePi nanosheets with rich vacancies as oxygen evolving electrocatalysts: Insight into the local atomic environment

Metal phosphates are considered as advanced electrocatalysts for oxygen evolution reaction in metal-air batteries and water splitting devices. However, it is of huge challenge to expose more active sites due to the typical amorphous feature. Besides, proper defect engineering is promising to enhance the performance of electrocatalysts. Herein, we have successfully prepared disordered CoFePi nanosheets with rich vacancies from layered double hydroxide by a solution plasma method. The plasma can etch the interlayer anions to realize the physical exfoliation of layered double hydroxides. Meanwhile, the as-physically-exfoliated layered double hydroxides nanosheets are in-situ chemically-conversed to disordered CoFePi nanosheets by the NaH2PO4. The X-ray adsorption spectra results suggest the abundance of vacancies in the products. Cobalt tends to adjust the local structural rearrangement and to sustain the structure in the presence of a great deal of oxygen and metal vacancies. Under this adjustment, the crystal field is expected to be influenced in CoFePi. The oxygen and metal vacancies may be extensively present in MO6 octahedra layers, giving rise to a relative structure disorder and more unbonded speciec within the layers which provides more active sites in CoFePi. As a result, the disordered CoFePi nanosheets with rich vacancies could catalyse OER effectively.