Bifunctional electrocatalysts for oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) are necessary in the renewable energy systems. However, the kinetically slow and large energy-demanding procedures of oxygen electrocatalysis make the preparation of bifunctional catalysts difficult. In this work, we report a novel hierarchical GdFeO 3 perovskite oxide of a spherelike nanostructure and surface modification with the group X heterometal oxides. The nanostructured GdFeO 3 layer behaved as a bifunctional electrocatalyst in the oxygen electrocatalysis of OER and ORR. Moreover, the surface decoration with catalytically active PtO x + Ni/NiO nanoparticles enhanced the electrocatalytic performances substantially. Incorporation of mesoporous PtO x + Ni/NiO nanoparticles into the porous GdFeO 3 nanostructure enlarged the electrochemically active surface area and provided the interconnected nanostructures to facilitate the OER/ORR. The nanostructures were visualized by scanning electron microscopy and transmission electron microscopy images, and the surface area and pore size of nanoparticles were analyzed from N 2 adsorption/desorption isotherms. Tafel analysis indicates that surface modification effectively improves the kinetics of oxygen reactions and accordingly increases the electrocatalytic efficiency. Finally, the 2 wt % PtO x + NiO|GdFeO 3 (x = 0, 1, and 2) electrode achieved the enhanced OER performance with an overpotential of 0.19 V at 10 mA/cm 2 in an alkaline solution and a high turnover frequency of 0.28 s −1 at η = 0.5 V. Furthermore, the ORR activity is observed with an onset potential of 0.80 V and a half-wave potential (E 1/2 ) of 0.40 V versus reversible hydrogen electrode.

Electrochemical proton reduction is a promising energy storage method because H 2 molecule has a simple structure with a relatively low potential energy. Current interest in hydrogen catalysts has increased research efforts on synthetic analogs of hydrogenase active sites. In this study, we demonstrated the electrochemical H 2 evolution reactivity of [NNN R -Co(CH 3 CN) 3 ] 2+ (R CH 2 (1b), NCH 3 (2b)) complexes and examined a proton-relay process in the H 2 evolution reaction (HER). Upon one-electron reduction, the Co(II) ion center in a high-spin state dissociated a CH 3 CN ligand, while opening a reaction site. Cyclic voltammograms of the Co complexes indicated quasi-reversible Co(II/I) redox behaviors, and both complexes 1b and 2b showed catalytic H 2 evolution activity. Interestingly, 2b, assisted by a protonrelaying NCH 3 group, exhibited more efficient catalytic activity than 1b.

We describe electrochemical reactivity of a pincer-type [NNN-Fe(tBuNC)3](ClO4)2 complex. Upon electron-reduction, the Fe(I) species experienced disproportionation to Fe(0) and Fe(II). The electron-reduced Fe center dissociated a tBuNC ligand to make...