Precisely designing atomic metal-nitrogen-carbon (M-N-C) catalysts with asymmetric diatomic configurations and studying their structure-activity relationships for oxygen reduction reaction (ORR) are important for Zinc-air batteries (ZABs). Herein, a dual-atomic-site catalyst (DASC) with CoN₃S-MnN₂S₂ configuration is prepared for the cathodes of ZABs. Compared with Co-N-C (Mn-free) and CoMn-N-C (S-free doping), CoMn-N/S-C exhibits excellent half-wave potential (0.883 V) and turnover frequency (1.54 e s^-1 site^-1), surpassing most of the reported state-of-the-art Pt-free ORR catalysts. The CoMn-N/S-C-based ZABs achieve extremely high specific capacity (959 mAh g^-1) and good stability (350 h @5 mA cm^-2). Density functional theory (DFT) calculation shows that the introduction of Mn and S can break the electron configuration symmetry of the original Co 3d orbital, lower the d-band center of the Co site and optimize the desorption behavior of *OH intermediate, thereby increasing the ORR activity.

Electrolytic water splitting (EWS) is an attractive and promising technique for the production of hydrogen energy. Nevertheless, the sluggish kinetic rate of hydrogen/oxygen evolution reactions leads to a high overpotential and low energy efficiency. Up to date, Pt/Ir-based nanocatalysts have become the state-of-the-art EWS catalysts, but disadvantages such as high cost and low earth abundance greatly limit their applications in EWS devices. As an attractive candidate for the Pt/Ir catalysts, series of Ru-based nanomaterials have aroused much attention for their low price, Pt-like hydrogen bond strength, and high EWS activity. In particular, Ru-doped functional porous materials have been becoming one of the most representative EWS catalysts, which can not only achieve the dispersion and adjustment for active Ru sites, but also simultaneously solve the problems of mass transfer and catalytic conversion in EWS. In this review, the design and preparation strategies of Ru-doped functional porous materials toward EWS in recent years are summarized, including Ru-doped metal organic frameworks (MOFs), Ru-doped porous organic polymers (POPs), and their derivatives. Meanwhile, detailed structure–activity relationships induced by the tuned geometric/electronic structures of Ru-doped functional porous materials are further depicted in this review. Last but not least, the challenges and perspectives of Ru-doped functional porous materials catalysts are reasonably proposed to provide fresh ideas for the design of Ru-based EWS catalysts.

Developing an efficient, interface-rich, and free-standing non-noble-metal electrocatalyst is vital for the flexible zinc-air batteries (ZABs). Herein, a three-dimensional (3D) heterogeneous carbon-based flexible membrane was assembled by Co@carbon nanosheets/carbon nanotubes and hollow carbon nanofiber (Co@NS/CNT-CNF) as an efficient oxygen reduction reaction (ORR) catalyst with a positive half-wave potential of 0.846 V and a small Tafel slope of 79 mV·dec⁻¹. Meanwhile, the Co@NS/CNT-CNF electrode also exhibits excellent open-circuit voltage, peak power density, and long-time cycling stability in liquid-state ZABs (1.605 V, 163 mW·cm⁻², and 400 h) and flexible ZABs under flat/bending condition (1.47 V, 102 mW·cm⁻², and 80 h). Such heterogeneous flexible membrane architecture not only optimizes the electrolyte infiltration, but also provides capacious possibility for O₂ and electrolyte transfer. Meanwhile, work-function analyses coupled with density functional theory (DFT) results demonstrate that the electron transfer capability and metal–support interaction can be well optimized in the obtained Co@NS/CNT-CNF catalyst.

Cobalt hydroxide nanosheet is among the most popular oxygen evolution reaction (OER) catalyst yet still suffers from sluggish catalytic kinetics, limited activity, and poor stability. Here, an efficient in situ electrochemical reconstructed CoFe-hydroxides derived OER electrocatalyst was reported. The introduction of Fe promoted the transformation of Co²⁺ into Co³⁺ in CoFe-hydroxides nanosheet, along with the formation of abundant amorphous/crystalline interfaces. Thanks for the retained nanosheet microstructure, high valence Co³⁺ and Fe³⁺ species, and the amorphous/crystalline heterostructure interfaces, the as-designed electrochemical reconstructed CoFeOOH nanosheet/Ni foam (CoFeOOHNS/NF) electrode delivers 100 mA·cm⁻² in alkaline at an overpotential of 275 mV and can stably electrocatalyze water oxidation for at least 35 h at 100 mA·cm⁻². Meanwhile, the alkaline full water splitting electrolyzer achieves a current density of 10 mA·cm⁻² only at 1.522 V for CoFeOOHNS/NF‖Pt/C/NF, which is much lower than that of Ru/C/NF‖Pt/C/NF (1.655 V@10 mA·cm⁻²). This work paves the way for in-situ synergetic modification engineering of electrochemical active components.