A multi-phase catalyst coating, composed of a thin-film PrBa 0.8 Ca 0.2 Co 2 O 5+d (PBCC) decorated with nanoparticles (NPs) of BaCoO 3Àx and PrCoO 3Àx , has dramatically enhanced the rate of oxygen reduction reaction. Oxygen molecules adsorb and dissociate rapidly on the NPs due to enriched surface oxygen vacancies, while the dissociated oxygen species transport quickly through the PBCC film into the cathode.

PrBa0.8Ca0.2Co2O5+δ material has shown remarkable ORR activity and excellent CO2 tolerance, as confirmed by experimental and computational tools.

the demands for energy storage and conversion systems of high energy and power density increase rapidly. To meet the everincreasing demands, transition metal compounds have been widely studied as catalysts for chemical and energy transformation processes (e.g., oxygen reduction and evolution reaction) [1][2][3][4] and as electrode materials for rechargeable batteries [5][6][7] and supercapacitors. [8][9][10][11][12][13] For example, nickel hydroxides (Ni(OH) 2 ) have been successfully used in rechargeable alkaline batteries (due to their low-cost and high capacity) [5,14] and in hybrid supercapacitors (due to high rate capability). [15] Hybrid supercapacitors, composed of a capacitive electrode and a battery-type Faradaic electrode, have demonstrated significantly higher energy density than conventional carbon-based electrical double-layer capacitors (EDLCs), due largely to the higher capacity of the battery-type electrode and the broader voltage window of the electrode pair. [16][17][18][19][20] Moreover, hybrid supercapacitors can achieve much higher power density than rechargeable batteries. Typically, one electrode of a hybrid supercapacitor is a carbon-based material whereas the other electrode (i.e., battery-type electrode) is a lithium electroactive material (such as Sn [16] and Li 4 Ti 5 O 12 [21] ) or an anionic redox active transition metal-based oxide/hydroxide. [15,22] As a promising battery-type electrode for hybrid supercapacitor in alkaline electrolyte, Ni(OH) 2 usually exhibits a pair of distinctly separated Faradaic redox peaks due to its phase transition. [23] This material was widely reported as a "pseudocapacitive" material for supercapacitors in the past decade, [24][25][26][27][28][29][30] but has recently been regarded as a battery-type material because of its batterytype behavior in alkaline media. [31][32][33] However, Ni(OH) 2 electrodes usually suffer from an irreversible phase transition, [34,35] large volume variation, [14] and low electronic conductivity, [36] resulting in poor durability and limited rate capability.Numerous efforts have been devoted to addressing the above issues. In order to enhance the electronic conductivity, an electronically conductive second phase has been introduced [15,24,37] or Ni(OH) 2 has been grown on a conductive substrate. [28,38,39] As a highly conductive two-demonstrational material with high surface area, graphene is an ideal substrate to improve the electronic conductivity of Ni(OH) 2 . [15,24,40] To further improve Compact, light, and powerful energy storage devices are urgently needed for many emerging applications; however, the development of advanced power sources relies heavily on advances in materials innovation. Here, the findings in rational design, one-pot synthesis, and characterization of a series of Ni hydroxide-based electrode materials in alkaline media for fast energy storage are reported. Under the guidance of density functional theory calculations and experimental investigations, a composite electrode composed of Co-/Mn-substituted...