Tapping the Potential of High-Valent Mo and W Metal Centers for Dynamic Electronic Structures in Multimetallic FeVO(OH)/Ni(OH) 2 for Ultrastable and Efficient Overall Water Splitting.

Rationally designing a noble metal-free electrocatalyst for OER and HER is pivotal for large-scale energy generation via water splitting. A multimetallic electrocatalyst FeVO(OH)/Ni 0.86 Mo 0.07 W 0.07 (OH) 2 , aimed at tuning the electronic structure, is fabricated and shows considerable improvement in the water-splitting reaction kinetics, aided by low Tafel slope values of 24 mV/dec for OER and 67 mV/dec for HER, respectively. By taking advantage of (e̅-e̅) repulsions at the t 2g level, we introduced high-valency Mo and W to provide a viable path for π-electron donation from oxygen 2p orbitals to vacant Mo and W orbitals for a dynamic electronic structure and an interfacial synergistic effect, which optimized the bond lengths for reaction intermediates to facilitate water splitting. The hybrid catalyst FeVO(OH)/NiMoW(OH) 2 shows intrinsic activity and durability toward OER and HER tested for 48 h at a current density of 20 mA/cm 2 and a cell voltage of 1.65 V @ 20 mA/cm 2 .