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The quest for alternatives to Pt as an oxygen reduction electrocatalyst, possessing high activity, stability, and abundant reserves, holds great significance for H2/O2 fuel cells. Recently, metal‐nitrogen‐carbon (M‐N‐C) electrocatalysts have garnered substantial attention as promising substitutes. These electrocatalysts not only exhibit well‐defined structures but also offer the flexibility to adjust the central metal atoms and coordination atoms. It is beneficial in elucidating the active sites during the catalytic process and in the design of highly active electrocatalysts. In this review, the real active site of M‐N‐C electrocatalyst‐driven ORR is investigated in depth by in situ characterization techniques such as X‐ray absorption spectroscopy, Raman spectroscopy, Fourier‐transform infrared spectroscopy. It′s worth noting that the catalytic activity of M‐N‐C electrocatalysts originates from the dynamic evolution of electrocatalyst structure. Subsequently, we review various synthetic strategies, including the wet chemistry method, spatial confinement, and template‐assisted method, aimed at the rational design of M‐N‐C electrocatalysts. Moreover, recent progresses of M‐N‐C electrocatalysts with varying configurations, encompassing single‐atom, and double‐atom electrocatalysts are discussed, Finally, summary and perspectives on the development of M‐N‐C are provided. [ABSTRACT FROM AUTHOR]

The practical application of Li−S batteries is still limited by the fundamental problems of the insulation properties of sublimed S and the "shuttle effect" of polysulfides. S‐doped porous carbon cage (SPCC) obtained by the catalytic guidance methodology is employed as a highly efficient S host material for Li−S batteries, which presents the cage‐like morphology coupled with abundant pore channels. Compared to the undoped PCC, SPCC exhibits higher electrical conductivity. The composite of sublimed S and SPCC (S@SPCC) employed as cathode for Li−S batteries possesses a higher reversible capacity, superior rate capability and better durability in comparison with that of S@PCC cathode. The synergistic effect of robust matrix associated with good electrical conductivity and abundant pore channels of SPCC is beneficial for the fast electron transport and shorten the Li‐ion diffusion distance. Besides, S doping possesses the positive function to attract Li‐polysulfides, inhibiting the shuttle of Li‐polysulfides and contributing to the superior electrode behavior of the S@SPCC cathode. [ABSTRACT FROM AUTHOR]

The lack of highly efficient, inexpensive catalysts severely hinders the large‐scale application of electrochemical energy conversion technologies (e.g., electrochemical hydrogen evolution reaction (HER) for hydrogen production, metal–air batteries (Cathode: oxygen reduction reaction (ORR))). As a new class of nanomaterials with a high ratio of surface atoms and tunable composition and electronic structure, metal nanocluster (NCs) are promising candidates as catalysts. Herein, a novel catalyst using S,N‐doped carbon matrix (NSCSs) is synthesized to efficiently stabilize high density and ultra‐uniform ruthenium (Ru) nanoclusters (Ru@NSCSs) by small‐molecule self‐assembly pyrolysis approach. The obtained Ru@NSCSs catalyst exhibits outstanding HER activity in all pH conditions (especially with a low overpotential of 5 mV at a current density of 10 mA cm−2 in 1 m KOH) and excellent ORR performance (half‐wave potential (E1/2) of 0.854 V in 0.1 m KOH). Based on the experimental investigations and theoretical calculations, it is discovered that the S‐atom can modulate the electronic structure and optimization of redox states on the surficial sites of Ru NCs during the ORR process. This work provides a feasible strategy for understanding and regulating the metal–support interface of ultra‐uniform nanoclusters catalysts. [ABSTRACT FROM AUTHOR]

Interfacial engineering is a powerful method to improve the bifunctional electrocatalytic performance of pure phase catalysts. While it is expected to further optimize the electronic configuration of heterojunctions to boost the reaction kinetics in hydrogen/oxygen evolution reaction (HER/OER), but remains a challenge. Herein, a novel in situ hybrid heterojunction strategy is developed to construct 2D porous Co‐doped Ni/Ni3N heterostructure nanosheets (Co–Ni/Ni3N) by pyrolysis of partially cobalt substituted nickel‐zeolitic imidazolate framework (CoNi‐ZIF) nanosheets under NH3 atmosphere. A combined experimental and theoretical studies manifest that the hybrid heterostructures can display regulative electronic states and downshift d‐band center from the Fermi level, as well as optimize the adsorption energy of reaction intermediates, thus reducing the thermodynamic energy barriers and accelerating the catalytic kinetics. Consequently, benefitting from the optimized electronic configuration, hierarchical hollow nanosheets architecture, and abundant doped heterojunctions, the hybrid Co–Ni/Ni3N heterostructure catalyst exhibits efficient catalytic activity for both HER (60 mV) and OER (322 mV) at 10 mA cm−2 in alkaline media, which is 105 and 47 mV lower than that of pure Ni3N, respectively. The electrochemically active surface area of Co–Ni/Ni3N is two times higher than that of Ni3N. Furthermore, the coupled practical water electrolyzer requires a low voltage of 1.575 V to reach 10 mA cm−2, and it can be driven by a 1.5 V battery. This work highlights the interface engineering guidance for the rational establishment of hybrid interfaces by electronic modulation of interfacial effect for alkaline water splitting. [ABSTRACT FROM AUTHOR]

The key challenge for solar water oxidation is to develop photoanodes with high charge transfer and separation efficiency as well as rapid surface reaction kinetics. Herein, the double metal‐free carbon materials, including carbon dots (CDs) and ultra‐thin carbon nitride (UCN), were coupled with TiO2 nanorods (CDs/UCN/TiO2) to enhance photoelectrochemical (PEC) activity. Attributed to the integrated effect of UCN and CDs, the designed ternary CDs/UCN/TiO2 photoanode exhibits a photocurrent density of 1.43 mA cm−2, which is 3.0‐fold higher than that of the bare TiO2 nanorods. In detail, the UCN can efficiently accelerate the charge separation and restrict the electron/hole recombination, owing to the close contact heterojunction. Meanwhile, the CDs can significantly facilitate H2O2 decomposition, as demonstrated by scanning electrochemical microscopy (SECM), as they induce rapid reaction kinetics. Importantly, such constructed photoanodes modified with double metal‐free carbon materials provide great potential for future progress in PEC water splitting through a simple decoration strategy with metal‐free carbon materials. [ABSTRACT FROM AUTHOR]

It is a serious challenge to develop photoanodes with fast charge separation efficiency and surface reaction kinetics. Herein, the N doped carbon dot modified WO3 nanoflake (NCDs/WO3) is constructed by impregnation method. The resulting NCDs/WO3 exhibits an excellent photocurrent density of 1.42 mA cm−2 (1.0 V vs saturated calomel electrode, SCE) in 1 m H2SO4 solution under AM 1.5 G irradiation, which is 2.25 times higher than that of the pristine WO3. In addition, the onset potential of NCDs/WO3 photoanode represents a cathodic shift of 70 mV, indicating the charge separation and transfer process are both promoted. These results demonstrate N doped CD modified WO3 can further enhance the conductivity and electrochemical activity surface area, which contributes to the higher photoelectrochemical (PEC) performance. This work provides an efficient strategy for the development of doping carbon material with heteroatoms to increase the charge transfer and charge separation efficiency in PEC water oxidation. Nitrogen doped carbon dots modified WO3 nanoflakes are studied to strengthen the light absorption and to accelerate the charge separation and transfer efficiency of WO3 nanoflakes. Nitrogen doping improves the electrical conductivity and electrochemical activity surface area of carbon dots, which is beneficial for promoting the photoelectrochemical performance of WO3. [ABSTRACT FROM AUTHOR]