In-situ (001) crystal plane derived C, N-FeNbO4 microrods on Ni foam for alkaline water/seawater oxidation

The rational design of electrocatalysts with high catalytic activity and outstanding corrosion resistance is of great significance for achieving water/seawater oxidation. In this work, a three-dimensional microrod C, N-FeNbO 4 /NF was successfully synthesized for the first time via hydrothermal approach integrated with in-situ strategy to construct more 001 crystal planes. Specifically, fluoride ions (F − ) coordinate with Fe/Nb and selectively adsorb onto FeNbO 4 (001) crystal plane. During liquid-phase nucleation process, the oxide further crystallizes along z-axis into microrod. Furthermore, the abundant C and N sources from solutions are incorporated into FeNbO 4 lattice by in-situ doping, thus significantly enhancing intrinsic electrical conductivity and catalytic activity. Meanwhile, the C, N-FeNbO 4 deposits on largely conductive nickel foam (NF), offering water/seawater oxidation under high current density. According to density functional theory (DFT) calculations, the model of in-situ constructed C, N-FeNbO 4 (001) crystal plane displays large carrier concentration and more mobile electrons. In-situ infrared spectroscopy suggests that C, N-FeNbO 4 /NF hosts multiple types of catalytic active sites, and confirms oxygen evolution reaction (OER) progress by adsorption evolution mechanism. From in-situ differential electrochemical mass spectrometry, the OER product of C, N-FeNbO 4 /NF is O 2 ( m / z  = 32), showing large O 2 evolution efficiency. The “in-situ derivatization–functional synergy” strategy imparts good electrocatalytic performance to C, N-FeNbO 4 /NF. In 1 M KOH and natural seawater, their overpotentials, with just 325 mV and 339 mV individually, can be acquired under 100 mA cm −2 current density. Depending on Tafel curve, the C, N-FeNbO 4 /NF offers strong corrosion resistance (corrosion potential: −0.17 V). Besides, it retains 96.5% initial activity after operating 100 h at 100 mA cm −2 current density in natural seawater.