A/B-Site Management Strategy to Boost Electrocatalytic Overall Water Splitting on Perovskite Oxides in an Alkaline Medium

Abstract

In this paper, Pr0.7Sr0.3Co1–x Ru x O3 perovskite oxides were synthesized by the sol–gel method as bifunctional catalysts for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). The overpotentials of PSCR0.05 against HER and OER at 10 mA cm–2 were 319 and 321 mV in alkaline medium, respectively. The Tafel slopes of HER and OER were 87.32 and 118.1 mV/dec, respectively. PSCR0.05 showed the largest electrochemical active area, the smallest charge transfer resistance, and excellent long-term durability. Meanwhile, the PSCR0.05 electrocatalyst was applied for overall water splitting and its cell voltage was maintained at 1.77 V at 10 mA cm–2. The super-exchange interaction between adjacent RuO6–CoO6 octahedra in perovskite made of PSCR0.05 contains sufficient active sites (such as Co2+/Co3+, Ru3+/Ru4+, and O2 2–/O–). The increase of surface oxygen vacancy and active site is the main reason for the improvement of difunctional catalyst performance. In this work, the electrocatalytic performance of perovskite-type oxides was further optimized by the method of A- and B-site cationic doping regulation, which provides a new idea for perovskite-type bifunctional electrocatalysts.

Study on Water Splitting of the 214-Type Perovskite Oxides LnSrCoO4 (Ln = La, Pr, Sm, Eu, and Ga)

“…According to the results of the Tafel slope and C dl , a smaller Tafel slope and higher C dl do not necessarily indicate a lower overpotential, as observed in the cases of LaSrCoO 4 and GdSrCoO 4 . Moreover, nearly all current experimental results indicate that the magnitude of the impedance is directly proportional to the absolute value of overpotential, and the TOF value calculated from the LSV curve is inversely proportional to the absolute value of overpotential. , From the electrical conductivity and magnetic behavior of the bulk samples, they all exhibit paramagnetic semiconductor-like behavior at room temperature, and importantly, considering the nearly identical microscopic sizes of the samples and the fact that the active sites are all Co atoms, we can infer that the activity of these catalysts is closely related to their intrinsic conductivity.…”

“…ABO 3 perovskite oxides (113-type) are widely used in electrochemical research, including the hydrogen evolution reaction (HER), the oxygen evolution reaction (OER), and the oxygen reduction reaction (ORR), owing to their diverse elemental composition, unique electronic structure, and the presence of oxygen vacancies. − A-site atoms generally refer to alkali metals, alkaline earth metals, and rare-earth elements, while B-site atoms are commonly employed as active sites in catalytic reactions, encompassing transition metals such as Fe, Co, and Ni, as well as noble metals like Ru, Pt, and Ir. − Currently, effective strategies to improve the electrocatalytic activity of perovskite oxides mainly involve the substitution of A­(B) site elements, regulation of oxygen vacancies, enhancement of the specific surface area, and improvement of room-temperature electrical conductivity. For example, in PrSrCoO 3 , the OER performance of PrSrCo 0.95 Ru 0.05 O 3 exceeds that of commercial RuO 2 by replacing different proportions of Ru elements . In Pr 0.5 Sr 0.5 Co 0.8 Fe 0.2 O 3−δ , the electrochemical performance is significantly improved by reducing the grain size and increasing the specific surface areas …”

Modulating the active phase in perovskite LaCoO3 with B-site doping of Cu for efficient methanol reforming to produce hydrogen

“…24 Zhao et al believed that the chemical state of B-site elements is reflected in the change of the B–O bond length. 25 It is speculated that the reduction process causes a modification in the ion states of B-site components, which consequently leads to a variation in the lattice parameters. The perovskite crystal remained stable before and after the reaction, indicating its high structural stability.…”

One-Dimensional La0.2Sr0.8Cu0.4Co0.6O3−δ Nanostructures for Efficient Oxygen Evolution Reaction

“…The O 1s spectrum shown in Figure 4 f contains four characteristic peaks at 528.2, 529.4, 532.1, and 533.6 eV corresponding to lattice oxygen (O 2− ), adsorbed oxidative oxygen species (O − /O 2− 2 ), adsorbed molecular oxygen and hydroxyl groups (O 2 /OH − ), and adsorbed water molecules (H 2 O). Among them, O − /O 2− 2 are active sites for OER in alkaline solutions, and the presence of these sites has a positive impact on oxygen transport [ 71 , 72 , 73 ].…”