Lattice-oxygen-active (Bi_0.5Co_0.5)₂O₃ was successfully prepared through vacancy modulation and demonstrated great OER activity and performance.

Rationally designing bifunctional electrocatalysts for the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) with high activity and long term stability remains to be a big challenge. Herein, we report in situ synthesized uniform Ru-doped FeCoP (FeCoRuP) nanoarrays as a bifunctional electrocatalyst for highly efficient overall water splitting. The introduction of Ru modifies the electronic interaction between cation active sites due to the electronegativity difference, which also introduces more active sites by creating lattice defects and distortion. Benefiting from the rich active sites and the strong electronic interaction, the optimized Ru-doped FeCoP exhibits excellent HER activities (45 mV at 10 mA cm⁻²) and OER activity (214 mV at 20 mA cm⁻²), together with excellent long-term durability (110 h) in alkaline media. An overall water splitting cell in which both anode and cathode are composed of the FeCoRuP catalyst exhibits an ultralow voltage of 1.47 V at 10 mA cm⁻², which is superior to the benchmark 20% Pt/C‖IrO₂ electrodes (1.68 V at 10 mA cm⁻²). The present work offers a simple but effective approach to promote the overall water splitting performance of transition metal phosphides by modulating the electronic structure of active sites.

In this paper, we prepare heavily electron doped $\mathrm{L}{\mathrm{a}}_{0.04}\mathrm{B}{\mathrm{a}}_{0.96}\mathrm{Sn}{\mathrm{O}}_3$ (LBSO) thin films on a $\mathrm{SrTi}{\mathrm{O}}_3$ (STO) substrate by the pulsed laser deposition method under different oxygen pressures, in which different levels of oxygen vacancy concentrations are present. Normally, oxygen vacancies are implicitly assumed as isolated point defects that dope the materials with electron carriers, whereas oxygen-deficient LBSO films exhibit an apparent metal-to-insulator transition combined with lower carrier concentrations and mobility with increased oxygen vacancies, which are concluded from the transport measurement data. Considering the almost constant density of threading dislocations and the higher formation energies for other intrinsic crystal defects, the observed transport trends are ascribed to the extra oxygen vacancies introduced. Therefore, strong electron localization originating from the interaction between the oxygen vacancy and La impurity is proposed for interpreting the behavior in oxygen-deficient LBSO films. Oxygen-deficient crystal structure models for LBSO have been optimized and the electronic structures are revealed by first-principles calculations based on the density functional theory. The partial density of states results indicate that strong electron localization comes from the deep strongly localized states in the forbidden gap, which are mainly composed of hybridized orbitals of $\mathrm{O}2p$ with $\mathrm{Sn}5s5p$ and some amount of $\mathrm{Sn}4d$. Thus, the control of the oxygen defects and the related electronic states in barium stannate is essential for achieving optimal electrical performance and as potential applications in perovskite heterostructure devices.