Tuning A-Site Cation Deficiency in Pr0.5La0.5BaCo2O5+ δ Perovskite to Realize Large-Scale Hydrogen Evolution at 2000 mA cm-2.

Industrial-level hydrogen production from the water electrolysis requires reducing the overpotential (η) as much as possible at high current density, which is closely related to intrinsic activity of the electrocatalysts. Herein, A-site cation deficiency engineering is proposed to screen high-performance catalysts, demonstrating effective Pr0.5- xLa0.5BaCo2O5+ δ (P0.5- xLBC) perovskites toward alkaline hydrogen evolution reaction (HER). Among all perovskite compositions, Pr0.4La0.5BaCo2O5+ δ (P0.4LBC) exhibits superior HER performance along with unique operating stability at large current densities (J = 500-2000 mA cm-2 geo). The overpotential of ≈636 mV is achieved in P0.4LBC at 2000 mA cm-2 geo, which outperforms commercial Pt/C benchmark (≈974 mV). Furthermore, the Tafel slope of P0.4LBC (34.1 mV dec-1) is close to that of Pt/C (35.6 mV dec-1), reflecting fast HER kinetics on the P0.4LBC catalyst. Combined with experimental and theoretical results, such catalytic activity may benefit from enhanced electrical conductivity, enlarged Co-O covalency, and decreased desorption energy of H* species. This results highlight effective A-site cation-deficient strategy for promoting electrochemical properties of perovskites, highlighting potential water electrolysis at ampere-level current density.

Synergistic Interaction of Double/Simple Perovskite Heterostructure for Efficient Hydrogen Evolution Reaction at High Current Density.

Electrocatalytic hydrogen production for industrial level requires highly active and cost-effective catalysts at large current densities. Herein A-site Ba-deficient double perovskite PrBa0.94 Co2 O5+ δ (PB0.94 C) is used as a precursor for fabricating PB0.94 C-based double/simple perovskite heterostructure (PB0.94 C-DSPH). PB0.94 C-DSPH with enhanced electrochemical surface area, more hydrophilic surface, and high conductivity ensures abundant active sites, rapid release of gas, and efficient charge transfer at high current densities. The resultant PB0.94 C-DSPH delivers the overpotential of 364 mV at a current density of 500 mA cm-2 for hydrogen evolution reaction in 1.0 m KOH solution, along with excellent long-term durability. Promisingly, the electrolyzer with PB0.94 C-DSPH cathode and NiFe-layered double hydroxide anode demonstrates high performance for overall water splitting by yielding high current density of 500 mA cm-2 at 1.93 V. Density functional theory calculations indicate that the double/simple perovskite heterostructure promotes the water adsorption, the dissociation of molecular H2 O, and the OH* desorption considerably, which controls the whole hydrogen evolution process. The proposed PB0.94 C-DSPH solves the problem of low hydrogen-evolution efficiency at high current density faced by noble metal-based catalysts in basic environment. This study may provide a route to explore high-demand elements in the earth for addressing the critical catalysts in clean-energy utilizations.

A-Site Cation-Ordering Layered Perovskite EuBa0.5Sr0.5Co2-x Fe x O5+δ as Highly Active and Durable Electrocatalysts for Oxygen Evolution Reaction.

The developments of high-performance and tolerant catalysts may enable more sustainable energy in the future, especially toward water oxidation. Herein, we report A-site cation-ordering layered perovskite EuBa0.5Sr0.5Co2-x Fe x O5+δ (EBSCFx) (x = 0.2-0.6) electrocatalysts. When evaluated for oxygen evolution reaction (OER) in alkaline media, EuBa0.5Sr0.5Co1.6Fe0.4O5+δ (EBSCF0.4) exhibits the best catalytic activity among all of these catalysts, as evidenced by the lowest overpotential of 420 mV at a current density of 10 mA cm-2. Notably, the catalytic activity of EBSCF0.4 is better than that of commercial IrO2 at the overpotential >460 mV. Furthermore, the EBSCF0.4-20RuO2 (involving 20 wt % RuO2) composite catalyst is developed and gives an overpotential as low as 390 mV at 50 mA cm-2, which is even superior to commercial RuO2. For overall water splitting, an electrolysis voltage of merely 1.47 V is achieved at 10 mA cm-2 in an electrolyzer employing EBSCF0.4-20RuO2 as bifunctional catalysts, with exceptional durability for 24 h. Such a performance outperforms state-of-the-art IrO2∥Pt/C and RuO2∥Pt/C couples. According to density functional theory (DFT) calculations, the unique catalytic properties of EBSCF0.4 may benefit from highly active Fe sites with octahedral coordination, and the synergistic effects of Fe and Ru sites in the composite catalyst accelerate the electrochemical water oxidation.