The development of low-cost, high-efficiency, and robust electrocatalysts for the oxygen evolution reaction (OER) is urgently needed to address the energy crisis. In recent years, non-noble-metal-based OER electrocatalysts have attracted tremendous research attention. Beginning with the introduction of some evaluation criteria for the OER, the current OER electrocatalysts are reviewed, with the classification of metals/alloys, oxides, hydroxides, chalcogenides, phosphides, phosphates/borates, and other compounds, along with their advantages and shortcomings. The current knowledge of the reaction mechanisms and practical applications of the OER is also summarized for developing more efficient OER electrocatalysts. Finally, the current states, challenges, and some perspectives for non-noble-metal-based OER electrocatalysts are discussed.

The exploration of highly active, durable, and cost-effective electrocatalysts for the oxygen reduction reaction (ORR) is indispensable for several important energy conversion technologies. Significant achievements have been made with numerous efforts devoted by the academic and industrial researchers. In this review, from a more practical point of view, the tests and experiments at the membrane electrode assembly (MEA) level are accentuated due to the fact that the rotating disk electrode (RDE) level performance cannot be transformed directly into the MEA level. Four major categories of the current ORR electrocatalysts are discussed, namely, platinum group metal (PGM or noble) catalysts, non-PGM catalysts, carbon-based catalysts, and single-atom-based catalysts. The advantages and shortcomings, along with the performance achieved by the catalysts, are briefly reviewed, and the improvement in the rational design approaches is emphasized at the full-cell level. Finally, the present challenges and prospects are discussed for developing advanced ORR electrocatalysts.

Porous CoFe O /C NRAs supported on nickel foam@NC (denoted as NF@NC-CoFe O /C NRAs) are directly fabricated by the carbonization of bimetal-organic framework NRAs grown on NF@poly-aniline(PANI), and they exhibit high electrocatalytic activity, low overpotential, and high stability for the oxygen evolution reaction in alkaline media.

Postsynthetic ion exchange of [Co2(μ-Cl)2(btta)] (MAF-X27-Cl, H2bbta =1H,5H-benzo(1,2-d:4,5-d')bistriazole) possessing open metal sites on its pore surface yields a material [Co2(μ-OH)2(bbta)] (MAF-X27-OH) functionalized by both open metal sites and hydroxide ligands, giving drastically improved electrocatalytic activities for the oxygen evolution reaction (an overpotential of 292 mV at 10.0 mA cm(-2) in 1.0 M KOH solution). Isotope tracing experiments further confirm that the hydroxide ligands are involved in the OER process to provide a low-energy intraframework coupling pathway.

In view of the clean and sustainable energy, metal–organic frameworks (MOFs) based materials, including pristine MOFs, MOF composites, and their derivatives are emerging as unique electrocatalysts for oxygen reduction reaction (ORR). Thanks to their tunable compositions and diverse structures, efficient MOF‐based materials provide new opportunities to accelerate the sluggish ORR at the cathode in fuel cells and metal–air batteries. This Minireview first provides some introduction of ORR and MOFs, followed by the classification of MOF‐based electrocatalysts towards ORR. Recent breakthroughs in engineering MOF‐based ORR electrocatalysts are highlighted with an emphasis on synthesis strategy, component, morphology, structure, electrocatalytic performance, and reaction mechanism. Finally, some current challenges and future perspectives for MOF‐based ORR electrocatalysts are also discussed.

Rational design and synthesis of highly active and robust bifunctional non‐noble electrocatalysts for both oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) are urgently required for efficient rechargeable metal–air batteries. Herein, abundant MnO/Co heterointerfaces are engineered in porous graphitic carbon (MnO/Co/PGC) polyhedrons via a facile hydrothermal‐calcination route with a bimetal–organic framework as the precursor. The in situ generated Co nanocrystals not only create well‐defined heterointerfaces with high conductivity to overcome the poor OER activity but also promote the formation of robust graphitic carbon. Owing to the desired composition and formation of the heterostructures, the resulting MnO/Co/PGC exhibits superior activity and stability toward both OER and ORR, which makes it an efficient air cathode for the rechargeable Zn–air battery. Importantly, the homemade Zn–air battery is able to deliver excellent performance including a peak power density of 172 mW cm−2 and a specific capacity of 872 mAh g−1, as well as excellent cycling stability (350 cycles), outperforming commercial mixed Pt/C||RuO2 catalysts. This work highlights the synergy from heterointerfaces in oxygen electrocatalysis, thus providing a promising approach for advanced metal–air cathode materials.

Novel NiCo2O4 NSs@HNRAs are fabricated via a simple and environmental friendly template-assisted electrodeposition followed by thermal annealing and they exhibit predominant electrochemical properties and long-term cycle stability.

Delicate design of nanostructures for oxygen‐evolution electrocatalysts is an important strategy for accelerating the reaction kinetics of water splitting. In this work, Ni–Fe layered‐double‐hydroxide (LDH) nanocages with tunable shells are synthesized via a facile one‐pot self‐templating method. The number of shells can be precisely controlled by regulating the template etching at the interface. Benefiting from the double‐shelled structure with large electroactive surface area and optimized chemical composition, the hierarchical Ni–Fe LDH nanocages exhibit appealing electrocatalytic activity for the oxygen evolution reaction in alkaline electrolyte. Particularly, double‐shelled Ni–Fe LDH nanocages can achieve a current density of 20 mA cm−2 at a low overpotential of 246 mV with excellent stability.