Enhancing the activity of FeNi bimetallic electrocatalysts on overall water splitting by Nd2O3-induced FeNi lattice contraction

The development of high-efficiency and cost-effective bifunctional electrocatalysts for overall water splitting remains a formidable challenge. Herein, FeNi-Nd2O3 nanoparticles anchored on N-doped carbon nanotubes (FeNi-Nd2O3/NCN) are designed for highly effective overall water splitting via a facile two-step hydrothermal approach. The synthetic FeNi-Nd2O3 hetero-trimers (Fe 2p-Ni 2p-Nd 3d orbital coupling) on NCN achieve excellent oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) activities with overpotentials of 270 and 120 mV at 10 mA cm−2 in 1 M KOH solution. Moreover, a small voltage of 1.52 V at 10 mA cm−2 is achieved when FeNi-Nd2O3/NCN is assessed as bifunctional catalyst for overall water splitting, which is superior to the typically integrated Pt/C and RuO2 counterparts (1.54 V at 10 mA cm−2). The related characterizations including X-ray absorption fine structure (XAFS) spectroscopy show that the remarkably improved activity is originated from Nd2O3-induced FeNi bimetallic lattice contraction. Furthermore, density functional theory (DFT) calculations indicate that the lattice contraction reduces binding energies of intermediates by downshifting the position of FeNi bimetallic d-band center relative to the Fermi level to optimize catalytic performance. Therefore, the Nd2O3-induced FeNi bimetallic lattice contraction may provide a new perspective for designing and synthesizing innovative catalytic systems.