Perovskite oxide is an attractive low-cost alternative catalyst for oxygen evolution reaction (OER) relative to the precious metal oxide-based electrocatalysts (IrO and RuO). In this work, a series of Sr-doped La-based perovskite oxide catalysts with compositions of LaSr FeO ( x = 0, 0.2, 0.5, 0.8, and 1) are synthesized and characterized. The OER-specific activities in alkaline solution increase in the order of LaFeO (LF), LaSrFeO (LSF-0.2), LaSrFeO (LSF-0.5), SrFeO (SF), and LaSrFeO (LSF-0.8). We establish a direct correlation between the enhancement in the specific activity and the amount of surface oxygen vacancies as well as the surface Fe oxidation states. The improved specific activity for LSF-0.8 is clearly linked to the optimum amount of surface oxygen vacancies and surface Fe oxidation states. We also find that the OER performance stability is a function of the crystal structure and the deviation in the surface La and/or Sr composition(s) from their bulk stoichiometric compositions. The cubic structure and lower deviation, as is the case for LSF-0.8, led to a higher OER performance stability. These surface performance relations provide a promising guideline for constructing efficient water oxidation.

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Although metallic ruthenium (Ru) is a potential electrocatalyst for the hydrogen evolution reaction (HER) to replace platinum (Pt) at a cost of only ≈4% of Pt, the persistent dissolution of Ru under operation conditions remains a challenge. Here, it is reported that agglomerates of large ruthenium phosphide (RuP) particles (L-RP, ≈32 nm) show outstanding HER performance in pH-universal electrolytes, which particularly demonstrates a surprisingly higher intrinsic activity and durability than small nanoparticles of RuP (S-RP, ≈3 nm) or metallic Ru on carbon supports. This is especially true in basic media, achieving electrocatalytic activity comparable to or even outperforming that of Pt/C, as reflected by lower overpotential at 10 mA cm , smaller Tafel slope, larger exchange current density, and higher turnover frequency while maintaining 200 h stable operation. Calculations suggest that ΔG of RuP is much closer to zero than that of metallic Ru, and phosphorous doping is proven to enhance the rate of proton transfer in HER, contributing in part to the improved activity of RuP. The better performance of L-RP than that of S-RP is ascribed largely to the stabilization of the P species due to the lowered surface energy of large particles. Furthermore, the relatively low-cost materials and facile synthesis make L-RP/C a highly attractive next-generation HER electrocatalyst.