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Three-dimensional ordered macroporous (3-DOM) IrO 2 was synthesized by using the silica colloidal crystal template method and explored as electrocatalyst for oxygen evolution reaction (OER) in acidic medium. X-Ray diffraction (XRD) patterns indicate that the prepared 3-DOM IrO 2 has a rutile structure. Images of scanning and transmission electron microscopies suggest that the 3-DOM IrO 2 possesses a hierarchical pore structure, in which the honeycomb array of 300 nm primary macropores were cross-linked by secondary mesopores on the walls. The presence of mesopores is also indicated by the N 2 adsorption/desorption isotherms and the small-angle XRD patterns. As compared with IrO 2 prepared by conventional colloidal method, the 3-DOM IrO 2 exhibited much larger BET area and voltammetric charges. Accordingly, about two and half times enhancement in OER activity was achieved by using 3-DOM IrO 2 as the electrode materials, showing prospect of 3-DOM materials in reducing the demand of the expensive IrO 2 electrocatalyst for OER in water electrolysis.

A porous N-doped carbon-encapsulated CoNi alloy nanoparticle composite (CoNi@N−C) was prepared using a bimetallic metal−organic framework composite as the precursor. The optimal prepared Co 1 Ni 1 @N−C material at 800 °C exhibited well-defined porosities, uniform CoNi alloy nanoparticle dispersion, a high doped-N level, and scattered CoNi−N x active sites, therefore affording excellent oxygen catalytic activities toward the reduction and evolution processes of oxygen. The oxygen reduction (ORR) onset potential (E onset ) on Co 1 Ni 1 @N−C was 0.91 V and the halfwave potential (E 1/2 ) was 0.82 V, very close to the parameters recorded on the Pt/C (20 wt Pt%) benchmark. Moreover, it is worth noting that the ORR stability of Co 1 Ni 1 @N−C was prominently higher than that of Pt/C. Under the oxygen evolution reaction condition, Co 1 Ni 1 @N−C generated the maximum current density at the potential of 1.7 V (8.60 mA cm −2 ) and the earliest E onset (1.35 V) among all Co x Ni y @N−C hybrids. The Co 1 Ni 1 @N−C catalyst exhibited the smallest ΔE value, confirming the superior bifunctional activity. The high surface area and porosity, and CoNi−N x active sites on the carbon surface including the proper interactions between the N-doped C shell and CoNi nanoparticles were attributed as the main contributors to the outstanding oxygen electrocatalytic property and good stability.