High‐Valence Metal Doping Induced Lattice Expansion for M‐FeNi LDH toward Enhanced Urea Oxidation Electrocatalytic Activities

Abstract The precise design of low‐cost, efficient, and definite electrocatalysts is the key to sustainable renewable energy. The urea oxidation reaction (UOR) offers a promising alternative to the oxygen evolution reaction for energy‐saving hydrogen generation. In this study, by tuning the lattice expansion, a series of M‐FeNi layered double hydroxides (M‐FeNi LDHs, M: Mo, Mn, V) with excellent UOR performance are synthesized. The hydrolytic transformation of Fe‐MIL‐88A is assisted by urea, Ni 2+ and high‐valence metals, to form a hollow M‐FeNi LDH. Owing to the large atomic radius of the high‐valence metal, lattice expansion is induced, and the electronic structure of the FeNi‐LDH is regulated. Doping with high‐valence metal is more favorable for the formation of the high‐valence active species, NiOOH, for the UOR. Moreover, the hollow spindle structure promoted mass transport. Thus, the optimal Mo‐FeNi LDH showed outstanding UOR electrocatalytic activity, with 1.32 V at 10 mA cm −2 . Remarkably, the Pt/C||Mo‐FeNi LDH catalyst required a cell voltage of 1.38 V at 10 mA·cm −2 in urea‐assisted water electrolysis. This study suggests a new direction for constructing nanostructures and modulating electronic structures, which is expected to ultimately lead to the development of a class of auxiliary electrocatalysts.