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Hydrogen peroxide (H2O2) is one of the 100 most paramount chemicals in the world, which has been widely used in industrial synthesis, pulp and bleaching, semiconductor cleaning, medical sterilizing, environmental treatments, and energy storage. Among various H2O2 production methods, anthraquinone process has intrinsic drawbacks such as energy‐intensive and environmental pollution while 2‐electron oxygen reduction reaction (ORR) provides an economic, efficient, and nonhazardous alternative process to realize the in situ production of H2O2 instead. Recently, heteroatom‐doped carbon electrocatalysts, especially the nitrogen‐doped ones, receive special attention due to the tunability on selectivity, activity, and stability towards ORR. In this review, the preparation methods on N‐doped carbon‐based electrocatalysts with different nitrogen forms are systematically classified, the mechanism of specific nitrogen morphology acting on two‐electron ORR is discussed, especially the selectivity, and the factors (pH, nitrogen content, active surface site density, physical properties of carbon substrates) affecting the ORR selectivity of N‐doped electrocatalysts are analyzed. Moreover, the preparation of H2O2 with N‐doped carbon materials in different experimental systems is also summarized. Finally, the development direction of H2O2 synthesis by 2‐electron ORR is prospected, and the suggestions from the aspects of production technology, testing method, and theoretical research are put forward. [ABSTRACT FROM AUTHOR]

[Display omitted] • Low-cost activated coke (AC) derived from coal was firstly utilized for H 2 O 2 electrogeneration. • AC-based gas diffusion electrode (GDE) was fabricated for effective H 2 O 2 production. • Effect of fabrication and operation parameters on H 2 O 2 production were systematically evaluated. • Synergistic effects of oxygen-containing groups towards 2eORR were studied by DFT calculation. Large-scale application of H 2 O 2 production through 2-electron oxygen reduction reaction (2eORR) greatly depends on the cost of electrode materials and configuration. In this work, engineered coal-derived oxygen-rich hierarchical activated coke (AC), which is low-cost and highly tunable in porosity and surface chemistry, was used as catalyst to fabricate gas diffusion electrodes (GDEs) for efficient H 2 O 2 production. Results showed that Fenton's reagents treatment could significantly increase the contents of C O and –COOH on AC, leading to an increased hydrophilicity. However, the higher O contents do not necessarily enhance the selectivity of AC towards 2eORR (i.e., F-5-AC, F-10-AC), especially that F-20-AC exhibited a complete 4e pathway. GDEs were then fabricated with AC and oxidized AC as catalyst, key fabrication parameters including the PTFE binder and AC particle size, and operating parameters such as current intensity, electrolyte pH, and O 2 flow rate were optimized. Up to 747 mg/L H 2 O 2 were generated within 90 min. Results showed that oxidized AC exhibited a decreased H 2 O 2 yield, due to the flooding of GDEs caused by super-hydrophilicity property. Finally, DFT calculations were employed to reveal the synergistic effect of different O groups considering the fact of high O contents on AC. [ABSTRACT FROM AUTHOR]

Hydrogen peroxide (H 2 O 2) electrosynthesis through oxygen reduction reaction (ORR) provides an environmentally-friendly alternative to the traditional anthraquinone process. While most studies focus on the original construction of active sites in electrocatalysts, it is also necessary to optimize the microenvironment in the dynamic catalytic process. Here, we proposed a pulse-induced strategy to achieve the in-situ regulation of active sites and interface microenvironment in ORR process, enabling a 210 % leap in H 2 O 2 yield and a 74 % increase in Faraday efficiency. A series of operando measurements revealed the stabilization effect on the catalyst morphology and oxygen-containing functional groups distribution, and the activation effect on the basal defect sites to strengthen the interaction with *O 2 and *OOH. Density functional theory calculations were further employed to reveal a unique ORR reaction pathway which decoupled the proton transfer and electron transfer process in pulsed electrocatalysis, providing new insights into the origin of ORR activity and selectivity. [Display omitted] • Exploring a strategy for dynamically regulating the active sites and interface microenvironment to promote H 2 O 2 production. • Achieving the in-situ stabilization of OGs and the dynamical activation of defects in O-doped carbon materials. • Providing unique insights into the origin of ORR activity and selectivity in pulsed-potential electrocatalysis. [ABSTRACT FROM AUTHOR]

Hydrogen peroxide (H 2 O 2) electrosynthesis from 2-electron O 2 reduction reaction (2eORR) is widely regarded as a promising alternative to the current industry-dominant anthraquinone process. Design and fabrication of effective, low-cost carbon-based electrodes is one of the priorities. Many previous work well confirmed that hydrophilic carbon-based electrodes are preferable for 2eORR. Here, we proposed a strategy of hydrophilicity-hydrophobicity regulation. By using commercially available graphite felt (GF) as electrodes, we showed that both hydrophilic GF, hydrophobic GF, and Janus GF yielded significantly higher H 2 O 2 production, which is 7.3 times, 7.6 times, and 7.7 times higher than the original GF, respectively. Results showed that currents and stirring rates affect the H 2 O 2 yields. The enhancement of hydrophilic GF is due to the incorporation of oxygen-containing functional groups, while the hydrophobic and Janus GF comes from the locally confined O 2 bubbles, which built a gas-liquid-solid interface inside GF and thus enhance the H 2 O 2 formation kinetics. Finally, the effectiveness of the hydrophilicity-hydrophobicity regulation concept was tested in Electro-Fenton process by removing typical dyes and antibiotics. This work supply an effective but facile strategy to enhance the performance of carbon-based electrodes towards 2eORR by regulating the micro-environment of electrodes. [Display omitted] • Increase of the hydrophilicity of graphite felt (GF) facilitated the H 2 O 2 electrogeneration. • Increase of the hydrophobicity increased the O 2 adsorption, thus increased the H 2 O 2 yield. • Janus GF exhibited a drastic enhancement on H 2 O 2 yield than the original one by 7 times. • Electro-Fenton enabled by the prepared electrodes was more effective for organics removal. • Hydrophilicity-hydrophobicity regulation is a promising strategy. [ABSTRACT FROM AUTHOR]

• Cost-effective activated coke catalyst is prepared towards H 2 O 2 production. • High activity, selectivity and stability are achieved in the typical alkaline system. • The coupling effects of carbon plane size and oxygen doping are evidenced. • A new activity descriptor of Fukui function is proposed to reveal active sites. Electrochemical oxygen reduction has been regarded as a promising choice to enable H 2 O 2 on-site production and utilization wherein the exploration of high-efficiency yet cost-effective catalysts is the key. Here, we demonstrate a low-cost activated coke (AC) electrocatalyst with size-tailored amorphous carbon clusters doped by oxygen groups, prepared through a facile CO 2 assisted mechanochemistry approach, to deliver among the highest performances reported in a typical alkaline system, including high activity (onset potential of 0.83 V), high H 2 O 2 selectivity (∼90 %) and long-term stability. A series of control experiments, structural characterizations before and after electrochemical tests and density functional theory calculations provide a new insight into the coupling role of carbon cluster size and oxygen doping in H 2 O 2 electrochemical production process, that is, size-reduced amorphous carbon lattices with abundant edges contribute to the high activity, while the basal carbon atoms in ether-doped small-size carbon plane are the most active sites towards H 2 O 2 selectivity. [ABSTRACT FROM AUTHOR]

• Recent advances in H 2 O 2 generation via 2-electron oxygen reduction (2eORR) are reviewed. • The H 2 O 2 electrosynthesis performances of various O-doped carbon cathodes are summarized. • The selectivities of various O functional groups toward 2eORR are discussed. • The synergistic effects of O and transition metals on 2eORR are systematically reviewed. • Future perspectives on O-doped carbon and Mn-O-C electrocatalysts are discussed. Hydrogen peroxide (H 2 O 2) electrosynthesis via the oxygen reduction reaction (ORR) presents an attractive decentralized alternative to the industry-dominant anthraquinone process. Oxidized carbon materials have proven to be promising catalysts due to their low cost and facile synthesis procedures. However, the nature of the active sites is still controversial. The objective of this paper is to provide a critical review of the advances of this topic. The fundamentals of the ORR pathway and O-doping effects are described, followed by the experimental preparation methods for O-doped carbon, including chemical oxidation and electrochemical oxidation. To identify the contribution of each oxygen-containing functional group (OG) or combination of OGs towards 2-electron ORR, combined experimental and DFT calculation results were analyzed. This paper also reviews the new advancement in the co-doping of O and transition metals, which could realize high activity and high selectivity toward H 2 O 2 generation. Future directions in this fascinating field are also highlighted. [ABSTRACT FROM AUTHOR]