Zirconium‐Regulation‐Induced Bifunctionality in 3D Cobalt–Iron Oxide Nanosheets for Overall Water Splitting

• Published in: Advanced materials (Weinheim) Vol. 31; no. 28; pp. e1901439 - n/a
• Main Authors: Huang, Liangliang, Chen, Dawei, Luo, Gan, Lu, Ying‐Rui, Chen, Chen, Zou, Yuqin, Dong, Chung‐Li, Li, Yafei, Wang, Shuangyin
• Format: Journal Article
• Language: English
• Published: Germany Wiley Subscription Services, Inc 01.07.2019; Wiley Blackwell (John Wiley & Sons)
• Subjects: bifunctional electrocatalysts; cationic regulation; Cobalt ferrites; Electrocatalysts; Electronic structure; electronic structure regulation; hydrogen evolution reaction; Hydrogen evolution reactions; Iron oxides; Materials science; Metal foams; Morphology; Nanosheets; Oxides; oxygen evolution reaction; Oxygen evolution reactions; Slope stability; spinel‐structured oxides; Water splitting; Zirconium; oxygen evolution reaction; bifunctional electrocatalysts; cationic regulation; spinel-structured oxides; electronic structure regulation; hydrogen evolution reaction
• ISSN: 0935-9648; 1521-4095; 1521-4095
• DOI: 10.1002/adma.201901439

The design of high‐efficiency non‐noble bifunctional electrocatalysts for oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) is paramount for water splitting technologies and associated renewable energy systems. Spinel‐structured oxides with rich redox properties can serve as alternative low‐cost OER electrocatalysts but with poor HER performance. Here, zirconium regulation in 3D CoFe2O4 (CoFeZr oxides) nanosheets on nickel foam, as a novel strategy inducing bifunctionality toward OER and HER for overall water splitting, is reported. It is found that the incorporation of Zr into CoFe2O4 can tune the nanosheet morphology and electronic structure around the Co and Fe sites for optimizing adsorption energies, thus effectively enhancing the intrinsic activity of active sites. The as‐synthesized 3D CoFeZr oxide nanosheet exhibits high OER activity with small overpotential, low Tafel slope, and good stability. Moreover, it shows unprecedented HER activity with a small overpotential of 104 mV at 10 mA cm−2 in alkaline media, which is better than ever reported counterparts. When employing the CoFeZr oxides nanosheets as both anode and cathode catalysts for overall water splitting, a current density of 10 mA cm−2 is achieved at the cell voltage of 1.63 V in 1.0 m KOH. CoFe2O4 after incorporation of zirconium tunes the nanosheet morphology and electronic structure around the Co and Fe sites for optimizing the adsorption energies, thus effectively enhancing the intrinsic activity of the active sites. Thus, the as‐synthesized optimal electrocatalyst of 3D zirconium‐regulated CoFe2O4 (CoFeZr oxides) nanosheets exhibits superior bifunctional OER and HER activities for overall water splitting.