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The electrocatalytic oxygen reactions, i.e. oxygen reduction/evolution reactions (ORR/OER), play a key role in electrochemical energy conversion and storage devices, including fuel cells, electrolyzers, and metal-air batteries, and have attracted significant attention in the past decades. Platinum-group metal (PGM)-free materials have been intensively investigated as alternatives to replace the well-accepted but costly PGM-based catalysts such as Pt for ORR and Ir/Ru (oxides) for OER. Particularly, metal-organic framework (MOF)-derived carbon materials are emerging PGM-free catalysts for ORR/OER. So far, excellent works have been achieved to enhance the activity and durability of the MOF-derived PGM-free catalysts. It is the occasion to promote the PGM-free catalysts to the next level of application, i.e. in real devices. However, ORR/OER in real devices are potentially subject to the porosity related challenges, e.g. electron/mass transfer issue and active site isolation in organic Li-air batteries. To address these challenges, the rational design of porous electrocatalyst for devices is required. In this review, we summarize the most recent progress of MOF-derived carbon materials for ORR/OER with the focus on not only the active site engineering but also the design of porous structure. We also provide perspectives on the rational design of PGM-free catalysts using MOF as precursors.

Oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) play crucial roles in energy conversion and storage devices. Particularly, the bifunctional ORR/OER catalysts are core components in rechargeable metal–air batteries, which have shown great promise in achieving "carbon emissions peak and carbon neutrality" goals. However, the sluggish ORR and OER kinetics at the oxygen cathode significantly hinder the performance of metal–air batteries. Although noble metal-based catalysts have been widely employed in accelerating the kinetics and improving the bifunctionality, their scarcity and high cost have limited their deployment in the market. In this review, we will discuss the ORR and OER mechanisms, propose the principles for bifunctional electrocatalysts design, and present the recent progress of the state-of-the-art bifunctional catalysts, with the focus on non-noble metal-based materials to replace the noble metal catalysts in Zn–air batteries. The perspectives for the future R&D of bifunctional electrocatalysts will be provided toward high-performance Zn–air batteries at the end of this paper.

International audience; The worldwide fossil fuel shortage and resultant environmental issues urgently require renewable and clean energy technologies. Electrocatalytic oxygen reduction/evolution reactions (ORR/OER) are the cornerstone for renewable energy conversion and storage devices, such as fuel cells, electrolyzers, unitized regenerative fuel cells, and metal‐air batteries. High‐performance electrocatalysts are required to improve the ORR and OER activity and stability, and thus the device performance. Therefore, appropriate strategies and methods are crucial for the rational design and synthesis of highly efficient ORR/OER electrocatalysts. On the other hand, the conventional platinum‐group‐metal‐based (PGM‐based) catalysts, such as Pt and Ir/Ru (oxides), have been facing great challenges, including limited resources and high cost, leading to them being less competitive in the market. Thus, a lot of effort has been devoted to developing alternative PGM‐free ORR/OER catalysts, which, however, still suffer from low activity and insufficient stability. In this review paper, the strategies for engineering high‐performance PGM‐free ORR and OER electrocatalysts are discussed by reviewing the most recent advances. At the end, perspectives on the methods to rationally design PGM‐free ORR and OER catalysts are provided.

A synergistic Pd–C catalytic hydrogenation of 4-pyridinecarboxamides straightforward to 4-piperidinecarboxamide hydrochlorides was developed in the presence of ClCH 2 CHCl 2 . It provided a novel strategy for highly efficient hydrogenation of pyridine nuclear by using low-cost Pd–C catalyst under mild conditions.

Pd–C catalyzed hydrogenolysis of benzaldehydes to methylbenzenes has been described to proceed via a ‘benzenemethanol pathway’. In this article, a novel ‘acetal pathway’ was first revealed by a systematic study when lower alcohols were used as solvents and a solvent-controlled highly efficient procedure was established.

A synergistic Pd–C catalytic hydrogenation of 4-pyridinecarboxamides straightforward to 4-piperidinecarboxamide hydrochlorides was developed in the presence of ClCH 2 CHCl 2 . It provided a novel strategy for highly efficient hydrogenation of pyridine nuclear by using low-cost Pd–C catalyst under mild conditions.

In the presence of 1,1,2-trichloroethane, a novel procedure for the Pd−C catalytic N-debenzylation of benzylamines was established. The method proceeded in a synergistic catalytic system and directly gave the products as crystal amine hydrochlorides in practically quantitative yields.

In the presence of 1,1,2-trichloroethane, a novel procedure for the Pd−C catalytic N-debenzylation of benzylamines was established. The method proceeded in a synergistic catalytic system and directly gave the products as crystal amine hydrochlorides in practically quantitative yields.

The mixed acid (H 2 SO 4 -HOAc) catalyzed ring opening of α,β-epoxyketone was the most used method for the preparation of diosphenols, but it seriously suffered from poor yields and -tedious workup operations. By using silica gel supported mixed acid (H 2 SO 4 -HOAc), a variety of α,β-epoxyketones were converted into the corresponding diosphenols in unprecedented high yields within a few minutes.