Exploration of the highly efficient bi‐functional catalysts toward the reduction of CO2 and decomposition of Li2CO3 at the cathode is the key for high‐performance Li‐CO2 batteries. Herein, topological defect‐rich graphene (TDG) based materials are developed as metal‐free cathodes for Li‐CO2 batteries, presenting an unprecedented full discharge capacity of over 69 000 mA h g−1 at the current density of 0.5 A g−1, a relatively small voltage gap of 1.87 V (Li/Li+) even at an extremely high current density of 2.0 A g−1, and an excellent long‐term stable cycle life of up to 600 cycles at 1.0 A g−1. The outstanding performance of Li‐CO2 batteries with the TDG cathodic electrocatalyst can be attributed to the introduction of topological defects in the carbon skeleton, providing sufficient active sites for CO2 reduction and evolution to facilitate the formation/decomposition of Li2CO3 during the discharging/charging process. The density functional theory calculations reveal the superiority of the negatively charged C atoms in topological defects as the adsorption for CO2 molecules and the activation sites for the decomposition of Li2CO3, and that the heterocyclic pentagon ring (C5) has a relatively low theoretical potential gap (1.01 V) during the charge and discharge processes.

Oxygen reduction reaction (ORR) is vital for clean and renewable energy technologies, which require no fossil fuel but catalysts. Platinum (Pt) is the best‐known catalyst for ORR. However, its high cost and scarcity have severely hindered renewable energy devices (e.g., fuel cells) for large‐scale applications. Recent breakthroughs in carbon‐based metal‐free electrochemical catalysts (C‐MFECs) show great potential for earth‐abundant carbon materials as low‐cost metal‐free electrocatalysts towards ORR in acidic media. This article provides a focused, but critical review on C‐MFECs for ORR in acidic media with an emphasis on advances in the structure design and synthesis, fundamental understanding of the structure‐property relationship and electrocatalytic mechanisms, and their applications in proton exchange membrane fuel cells. Current challenges and future perspectives in this emerging field are also discussed.

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A hollow PdCuMoNiCo high-entropy alloy on carbon hybrid was developed as a high-performance bi-functional electrocatalyst for the oxygen reduction reaction and formic acid oxidation reaction in an acidic medium.