Developing high-efficiency and low-cost nonprecious catalysts for the oxygen reduction reaction (ORR) is important but still challenging. Herein, a N-doped carbon catalyst embedded with uniformly dispersed Cu nanoparticles (∼30 nm) is fabricated by the spatial confinement effect of a nitrogen-rich Salen-based covalent organic framework (Salen-COF), in which Cu­(II) ions are anchored onto open chelate sites of Salen-COF and isolated by aromatic rings to form uniformly dispersed Cu nanoparticles embedded in N-doped carbon (Cu NPs/N-C) during pyrolysis. The optimized Cu NPs/N-C-800 exhibits high ORR catalytic activity in both alkaline and acidic electrolytes, especially with an onset potential (E onset) of 1.02 V and a half-wave potential (E 1/2) of 0.88 V in an alkaline electrolyte. Attractively, the Cu NPs/N-C-800-derived Zn–air battery demonstrates a higher peak-power density (163.5 mW cm–2) and long-term cycling stability (118 h). The electronic interaction between the highly concentrated homogeneously dispersed Cu NPs and carbon shell results in an appropriate d-band center, and the porous graphitized carbon shell leads to faster electron transfer and mass transport, which are responsible for the high ORR performance of Cu NPs/N-C-800. This strategy provides a new prospect to synthesize uniformly dispersed metal nanoparticle electrocatalysts with more exposed active sites and efficient catalytic activities for renewable energy conversion devices.

The hydrogen spillover effect on metal-supported electrocatalysts is of great significance in hydrogen-involved reactions, especially in a hydrogen oxidation reaction (HOR). Herein, a facile thermal reduction method has been adopted to synthesize W18O49 (WO2.72) nanospheres decorated with single nickel atoms, and the obtained Ni-WO2.72-T (1.20 wt % Ni) was used as a probe catalyst for investigating the hydrogen spillover effect, which exhibits enhanced HOR performance, stability, and resistance to CO poisoning in acidic electrolytes. Based on in situ Raman spectroscopy and the density functional theory (DFT) calculation, a synergistic effect between Ni single-atom active sites and the hydrogen spillover effect is proposed to contribute to the HOR performance on Ni-WO2.72-T. Briefly, the introduction of single Ni atoms induces electron redistribution on Ni-WO2.72-T, making Ni atoms positively charged for H2 adsorption and activation, and on the other hand, the reversible phase transformation between WO2.72 and H x WO2.72 facilitates H* transfer from Ni to WO2.72, i.e., hydrogen spillover, resulting in elevating the HOR catalytic activity. Both experimentation and theoretical calculations demonstrate that the reversible phase transformation of the WO2.72 substrate strengthens the hydrogen spillover effect and thus elevates the HOR catalytic performance, which is believed to be helpful in designing highly active catalysts for hydrogen-involving reactions.

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Developing cost–benefit and high‐performance non‐noble metal oxygen reduction reaction (ORR) electrocatalysts is highly imperative for wide applications of renewable energy conversion devices. Herein, a one stone two birds phosphorization strategy has been proposed to synthesize hollow structured Cu/Cu3P heterogeneous nanoparticles supported on N, P co‐doped carbon (Cu/Cu3P@NP‐Cs). The optimized Cu/Cu3P@NP‐C‐900 features high ORR performance under both alkaline and acidic conditions. Moreover, the Cu/Cu3P@NP‐C‐900‐drivened Zn‐air battery exhibits a substantially higher power density output (148.2 mW cm−2) and stronger charge–discharge stability (300 h, 1805 cycles) than those of Pt/C‐equipped counterpart. The cross‐interface electron transfer from Cu3P to Cu effectively regulates the d‐band center of Cu/Cu3P, thereby leading to the balanced adsorption/desorption energy of oxygen species. Meanwhile, the hollow structure maximizes the exposure of accessible active centers, resulting in much accelerated ORR kinetics. This work proposes an innovative insight for developing hollow hetero‐structured catalysts to improve ORR performance.