New Way to Synthesize Robust and Porous Ni1-xFex Layered Double Hydroxide for Efficient Electrocatalytic Oxygen Evolution.

Traditional catalysts are usually synthesized by sputtering, electrochemical deposition, or hydrothermal methods, and they also need to be combined with substrates to obtain the working electrodes. Here we introduce a new route to produce an efficient catalyst for oxygen evolution reaction (OER) that is made by ball milling and sintering. By using Se as a grinding aid, the bulk electrode Ni1-xFexSe1.15 is obtained with high porosity and robust mechanical strength after sintering. Active Ni1-xFex layered double hydroxide (LDH) nanosheets are subsequently produced on the surface of the Ni1-xFexSe1.15 by in situ electrochemical oxidation. Compared with traditional synthesis methods, the new process displays superior advantages, such as producing an electrode that is substrate-free and exhibits robust mechanical strength as well as being cost-effective for mass production. Additionally, V- and Mn-doped Ni0.75Fe0.25-LDH exhibit comparable and competent OER performance in 1 M KOH solution. Ni0.71V0.04Fe0.25-LDH achieves current densities of 100 and 1000 mA cm-2 at overpotentials of 244 and 300 mV, respectively. This work demonstrates a promising way to synthesize highly efficient and robust electrocatalysts for water oxidation.