(215e) Strongly Coupled 3D Ternary Fe2O3@Ni2p/Ni(PO3)2 Hybrid for Enhanced Electrocatalytic Oxygen Evolution at Ultra-High Current Densities

Xiaodi Cheng^a, Zhiyan Pan^b, Chaojun Lei^a, Yangjun Jin^b, Bin Yang^a, Zhongjian Li^a, Xingwang Zhang^a, Lecheng Lei^a, Chris Yuan,^c Yang Hou^a,*

^aKey Laboratory of Biomass Chemical Engineering of Ministry of Education, College of Chemical and Biological Engineering, Zhejiang University, Hangzhou, China. E-mail: yhou@zju.edu.cn

^bEnvironmental Chemical and Resource Research Institute, College of Environment, Zhejiang University of Technology, Hangzhou, China.

^cDepartment of Mechanical and Aerospace Engineering, Case Western Reserve University, Cleveland, OH, 44106, USA.

Abstract

Developing highly efficient non-noble metal electrocatalysts for oxygen evolution reaction (OER) at large current densities remains as one of the primary challenges for water electrolyzesr. Construction of transition metal phosphides/phosphates based hybrid electrocatalysts possessing synergistic effects between different active components based on their advantages could satisfy the prerequisite of activity and stability for OER. Transition metal oxides featuring iron have become one of the most promising OER electrocatalysts thanks to its inherent catalytic activity associated with natural abundance. Therefore, how to construct a hybrid electrocatalyst combining multiple active contents is a key issue to designing high active OER materials. Meticulous design and synthesis of the active sites of the electrocatalysts, and in-depth understanding of the catalytic mechanism are crucial for the development of new catalytic materials with sufficient active sites, thus realizing efficient water splitting.

Herein, we developed a novel 3D strongly coupled ternary hybrid composed of Ni₂P/Ni(PO₃)₂ and Fe₂O₃ grown on the 3D Ni foam through a disproportionation reaction. In this 3D hybrid structure, the Fe₂O₃@Ni₂P/Ni(PO₃)₂ nanoparticles with length of ~300 nm and width of ∼200 nm are homogeneously grown on the surface of 3D Ni foam. The outstanding OER activity can be attributed to the synergetic effect and strong coupling effect between the Fe₂O₃ and Ni₂P/Ni(PO₃)₂. In situ Raman spectroscopy revealed that the NiOOH and FeOOH phases were the real active species in the Fe₂O₃@Ni₂P/Ni(PO₃)₂/NF for OER. The excellent OER catalytic activity of 3D Fe₂O₃@Ni₂P/Ni(PO₃)₂/NF could be donated to the synergic effect among the Fe₂O₃, Ni₂P, and Ni(PO₃)₂ in addition to strong coupling effect. The NiOOH and FeOOH species acted as the active phases in Fe₂O₃@Ni₂P/Ni(PO₃)₂/NF during OER process was proved through in situ Raman spectroscopy.

The 3D Fe₂O₃@Ni₂P/Ni(PO₃)₂/NF hybrid achieves a superior electrocatalytic oxygen evolution reaction OER) performance at ultra-high current densities in alkaline electrolyte. The catalytic current densities of 500 and 1000 mA cm^−2 are reached by applying only potentials of 1.57 and 1.60 V, respectively, which are almost the lowest potentials among all previously reported transition metal (Ni and Fe) based phosphides and phosphates electrocatalysts (Nat. Commun., 2018, 9, 2551; Energy Environ. Sci., 2018, 11, 1287-1298, etc.), and even better than that of the benchmark Ir/C catalyst (1.64 and > 1.8 V at 100 and 500 mA cm^−2). Furthermore, In addition to the admirable OER activity and stability, the bifunctional 3D Fe₂O₃@Ni₂P/Ni(PO₃)₂/NF delivered a cell voltage of 1.93, 2.48, and 3.02 V at 100, 500, and 1000 mA cm^−2 toward overall-water-splitting.

Biography

Xiaodi Cheng received his bachelor's degree from Chemical Engineering Institute of Jinggangshan University in 2017. He is currently a Master in College of Chemical and Biological Engineering, Zhejiang University. His current research focuses on the design and synthesis of Ni-Fe based hybrids for energy and environmental applications.