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Due to structural complexity and limited understanding, precise chemical modification in atomically dispersed metal-nitrogen-carbon (M-N-C) catalysts requires theoretical calculations to optimize electronic, geometric, and catalytic performance and experimental implementation of learned lessons to improve their catalytic performance towards oxygen reduction reaction (ORR). Herein, we conducted a density functional theory (DFT) investigation to understand the effect of the replacement of O-atoms in Fe–O 4 –C by N-atoms in the first coordination shell of Fe-site (constructing five models: Fe–O 4 –C, Fe–O 3 N–C, Fe–N 2 O 2 –C, Fe–ON 3 –C and Fe–N 4 –C) towards ORR. The geometric and electronic calculations of these models suggested that replacing all the O-atoms with N-atoms around the Fe-site would make it more conducive to the adsorption of ORR intermediates. Moreover, the Gibbs free energy calculations demonstrated that the Fe-site becomes the active centre for 2e− ORR, leading to the dominant generation of H 2 O 2 when Fe is coordinated with four O-atoms (Fe–O 4 –C). Whereas in compounds like Fe–N 2 O 2 –C, Fe–O 3 N–C, and Fe–N 4 –C, where the Fe-site displays 4e− ORR, form water is a preferred product if the O-atoms are replaced by N-atoms, as in Fe–N 2 O 2 –C, Fe–O 3 N–C, and Fe–N 4 –C. This study would provide a fundamental understanding of how atomically dispersed M-N-C catalysts' electrocatalytic activity is affected by changes in the coordination environment of metal sites. [Display omitted] • A theoretical approach was used to construct the models of Fe-NxOy-C-based electrocatalysts. • The models Fe–O 4 –C, Fe–NO 3 –C, M–N 2 O 2 –C, M–N 3 O–C, and M-N4-C, were completely investigated via DFT approaches. • The O 2 adsorption at the Fe–N 4 –C catalyst was the determining step during the associative pathway. • The M-N 4 -C catalytic moel displayed 4e- ORR, while the M-O 4 -C catalyst showed 2e- ORR. [ABSTRACT FROM AUTHOR]

Nitrogen‐doped, carbon‐supported transition metal catalysts are excellent for several reactions. Structural engineering of M−Nx sites to boost catalytic activity is rarely studied. Here, we demonstrate that the structural flexibility of Fe−N3 site is vital for tuning the electronic structure of Fe atoms and regulating the catalytic transfer hydrogenation (CTH) activity. By introducing carbon defects, we construct Fe−N3 sites with varying Fe−N bond lengths distinguishable by X‐ray absorption spectroscopy. We investigate the CTH activity by density‐functional theory and microkinetic calculations and reveal that the vertical displacement of the Fe atom out of the plane of the support, induced by the Fe−N3 distortion, raises the Fe 3dz2 ${3{d}_{{z}^{2}}{\rm \ }}$ orbital and strengthens binding. We propose that the activity is controlled by the relaxation of the reconstructed site, which is further affected by Fe−N bond length, an excellent activity descriptor. We elucidate the origin of the CTH activity and principles for high‐performing Fe−N−C catalysts by defect engineering. [ABSTRACT FROM AUTHOR]

The development of high-performance electrocatalysts for energy conversion reactions is crucial for advancing global energy sustainability. The design of catalysts based on their electronic properties (e.g., work function) has gained significant attention recently. Although numerous reviews on electrocatalysis have been provided, no such reports on work function-guided electrocatalyst design are available. Herein, a comprehensive summary of the latest advancements in work function-guided electrocatalyst design for diverse electrochemical energy applications is provided. This includes the development of work function-based catalytic activity descriptors, and the design of both monolithic and heterostructural catalysts. The measurement of work function is first discussed and the applications of work function-based catalytic activity descriptors for various reactions are fully analyzed. Subsequently, the work function-regulated material-electrolyte interfacial electron transfer (IET) is employed for monolithic catalyst design, and methods for regulating the work function and optimizing the catalytic performance of catalysts are discussed. In addition, key strategies for tuning the work function-governed material-material IET in heterostructural catalyst design are examined. Finally, perspectives on work function determination, work function-based activity descriptors, and catalyst design are put forward to guide future research. This work paves the way to the work function-guided rational design of efficient electrocatalysts for sustainable energy applications., (© 2024 The Authors. Advanced Materials published by Wiley‐VCH GmbH.)

The efficient energy conversion of hydroxide exchange membrane fuel cells (HEMFCs) is restrained by slow anodic hydrogen oxidation reaction (HOR) kinetics. Recently, Ru-based nanomaterials have emerged as the promising catalysts for alkaline HOR because of its much more attractive price advantage and reasonable intermediates binding ability, yet a comprehensive timely review on major achievements of Ru-based alkaline HOR catalysts is missing. Under the background, we aim to provide thorough knowledge of alkaline HOR on Ru-based catalysts, such as the developed mechanism viewpoints based on diverse experimental and advanced theoretical studies, the effective strategies to optimize both the catalytic activity and stability as well as the current progresses in the HEMFCs devices with Ru-anodes. Specifically, this review first covers three seemingly contradictive activity descriptors. In the following, the structure-activity relationship is shared to elucidate underlying performance improvement mechanisms. Then, the possible physical chemistry behind catalysts instability, including electrochemical degradations, oxides poisoning and CO susceptibility, is presented, and corresponding promising strategies for improving their stability are summarized. Next, the performance progresses of HEMFCs constructed by Ru-based anodic catalysts are provided. Finally, possible research directions for further enhancing Ru-based catalysts performance are suggested. Wherever is appropriate, our opinions are shared, hoping this review will serve as a guidance for the construction and development of efficient Ru-based catalysts for energy conversion. [Display omitted] • Three contradictive mechanisms may do carry rationality in one certain system. • Ru-based catalysts are optimized by increasing the quality or number of active sites. • Electrochemical degradations and poisoning should be controlled for good stability. • Ru-based catalysts without Pt can obtain equal HEMFCs performance to that of PtRu/C. [ABSTRACT FROM AUTHOR]

[Display omitted] • Advantages and optimization strategies for heteronuclear DACs towards their catalytic Activity are emphasized. • Advances in atomically precised heteronuclear DACs for electrocatalytic CO 2 RR are highlighted. • Correlations between structural characteristics of heteronuclear DACs and their CO 2 RR activity are discussed. • The key challenges and future direction with heteronuclear DACs-based materials are also explored. Inspired by nature's construction of the heteronuclear dual-atomic sites, Fe-Mo co-factor, for nitrogen fixation and the carbon cycle, researchers have focused extensively on developing heteronuclear dual-atomic site catalysts (HN-DACs) for electrochemical CO 2 reduction reactions (CO 2 RR). The HN-DACs, having different metal sites at a distance limit for the electronic interaction, can be promising models, offering one site for C-affinity and another site for O-affinity, thereby facilitating the breaking of the linear scaling relationship for CO 2 RR. Moreover, HN-DACs have excellent stability and selectivity due to the synergistic influence between heteronuclear dual-atomic sites, which affects the electronic structure and charge distribution over the whole DAC's surface. This review highlights the merits of DACs, in particular HN-DACs, and how they can break the linear scaling relationship towards CO 2 RR. The logical optimization strategies for HN-DACs and their synthesis, characterization, and stability are also discussed. Further, the recent advances in HN-DACs towards electrocatalytic CO 2 RR are extensively documented. Finally, challenges and future prospects with HN-DACs are also highlighted. [ABSTRACT FROM AUTHOR]

Energy storage technologies, such as fuel cells, ammonia production and lithium-air batteries, are important strategies for addressing the global challenge of energy crisis and environmental pollution. Taking overpotential as a direct criterion, we illustrate in theory and experiment that the adsorption energies of charged species such as Li+ +e- and H+ +e- are a central parameter to describe catalytic activities related to electricity-in/electricity-out efficiencies. The essence of catalytic activity is revealed to relate with electronic coupling between catalysts and charged species. Based on adsorption energy, some activity descriptors such as d-band center, eg-electron number and charge-transfer capacity are further defined by electronic properties of catalysts that directly affect interaction between catalysts and charged species. The present review is helpful for understanding the catalytic mechanisms of these electrocatalytic reactions and developing accurate catalytic descriptors, which can be employed to screen high-activity catalysts in future high-throughput calculations and experiments. [ABSTRACT FROM AUTHOR]

The sluggish cathodic oxygen reduction reaction (ORR) of proton exchange membrane fuel cells (PEMFCs) heavily relies on the employment of a large quantity of unaffordable Pt-based electrocatalysts to accelerate the slow kinetics. As switching from acidic proton exchange membrane to alkaline hydroxide one, it is highly promising to completely replace platinum group metal (PGM)-based ORR electrocatalysts with PGM-free counterparts. However, anodic hydrogen oxidation reaction (HOR), with a fast kinetics in PEMFCs even at a low Pt loading of 50 μg Pt cm −2 or less, becomes two orders of magnitude slower in alkaline media and thus requires a high loading of PGM-based electrocatalysts to accelerate the reaction rate. Alkaline HOR has drawn a great number of recent attentions, yet a comprehensive review is missing. Herein, this review covers diverse possible alkaline HOR mechanisms, hardly comparable electrocatalysts evaluation methods, two seemingly contradictive activity descriptors, as well as design and synthesis of PGM-based and PGM-free electrocatalysts with controlled structural parameters. Wherever is appropriate, this review describes our own point of view on certain subjects. Finally, future research directions are suggested. This review will provide knowledge and insights on fundamental and practical issues for the development of advanced alkaline HOR electrocatalysts and mechanism. [ABSTRACT FROM AUTHOR]

[Display omitted] • A fundamental understanding of ORR and electrocatalysts is provided. • Recent developments on non-noble-metal-based electrocatalysts for ORR are explored. • Correlations between science/engineering and existing activity descriptors to improve the electrocatalyst's ORR performance are highlighted. • Future aspects and challenges with non-noble-metal-based electrocatalysts are discussed. Metal-air batteries (MABs) and fuel cells (FCs) critically rely on electrocatalytic O 2 activation, and O 2 reduction reaction (ORR), with noble metal-free materials. However, the inception of their synergist reactivity is still unclear due to several electronic and structural limitations. Therefore, the correlation between their science and engineering and their experimental as well as theoretical activity descriptors can pave the way for the development of novel cheap, and efficient catalysts. Moreover, with this framework, several volcanic correlations were established, indicating that catalyst activity increases linearly with increasing binding energy of ORR intermediates up to a certain point, but after that, the activity decreases as binding energy increases. The motivation of this review is to highlight (i) recent designs and developments on non-noble-metal-containing electrocatalysts for ORR, (ii) correlations between science and engineering and existing activity descriptors to improve the electrocatalyst's ORR performance, and (iii) prospects and challenges with non-noble-metal-based electrocatalysts. The "science and engineering" of the electrode materials discussed in this review will aid researchers in selecting and designing ORR electrocatalysts for energy conversion processes. [ABSTRACT FROM AUTHOR]

Targeting tumor hydrogen peroxide (H 2 O 2 ) with catalytic materials has provided a novel chemotherapy strategy against solid tumors. Because numerous materials have been fabricated so far, there is an urgent need for an efficient in silico method, which can automatically screen out appropriate candidates from materials libraries for further therapeutic evaluation. In this work, adsorption-energy-based descriptors and criteria are developed for the catalase-like activities of materials surfaces. The result enables a comprehensive prediction of H 2 O 2 -targeted catalytic activities of materials by density functional theory (DFT) calculations. To expedite the prediction, machine learning models, which efficiently calculate the adsorption energies for 2D materials without DFT, are further developed. The finally obtained method takes advantage of both interpretability of physics model and high efficiency of machine learning. It provides an efficient approach for in silico screening of 2D materials toward tumor catalytic therapy, and it will greatly promote the development of catalytic nanomaterials for medical applications., (© 2023 Wiley-VCH GmbH.)

• This review highlights the fundamental roles of metallo-phthalocyanines for various electrocatalysis. • Discussion on activity descriptors for various electrocatalysis with metallo-phthalocyanines. • Summary on the going reports on metallo-phthalocyanines for energy applications. • Discussion on strategies to benchmark to performance of MN4-molecular electrocatalysts. • The difficulties and future directions for the metallo-phthalocyanines based materials at practical level. Metal phthalocyanines (MPcs) and their derivatives are not only considered as potential electrocatalysts for oxygen reduction reaction (ORR), oxygen and hydrogen evolution reaction (OER and HER) and carbon dioxide reduction reaction (CO 2 RR) but also as ideal models to understand the origin of activity of various electrocatalysts. The volcano correlations are usually used to understand the inception of synergistic reactivity of molecular electrocatalysts that the appropriate binding strength of reaction intermediate is essential. The M(III)/(II) redox potential, which was found to be the key activity descriptors for ORR process, while M(IV)/(III) and M(II)/(I) redox couples for OER, HER, and CO 2 RR, respectively. The aim of this review is (i) to simplify the existing bridges between the quantum parameters of MPcs and their activities, (ii) to highlight the recent advancements on MPcs-based materials for ORR, OER, HER and CO 2 RR, and (iii) to emphasize the future aspects from the combined approach of molecular, supramolecular and material science engineering for above mentioned electrocatalysis. The efforts in this work presents the "systematic design principles" which may be useful for researchers in constructing electrode materials for energy processes. [ABSTRACT FROM AUTHOR]

With the potential to circumvent the need for scarce and cost-prohibitive platinum-based catalysts in proton-exchange membrane fuel cells, anion-exchange membrane fuel cells (AEMFCs) are emerging as alternative technologies with zero carbon emission. Numerous noble metal-free catalysts have been developed with excellent catalytic performance for cathodic oxygen reduction reaction in AEMFCs. However, the anodic catalysts for hydrogen oxidation reaction (HOR) still rely on noble metal materials. Since the kinetics of HOR in alkaline media is 2-3 orders of magnitude lower than that in acidic media, it is a major challenge to either improve the performance of noble metal catalysts or to develop high-performance noble metal-free catalysts. Additionally, the mechanisms of alkaline HOR are not yet clear and still under debate, further hampering the design of electrocatalysts. Against this backdrop, this review starts with the prevailing theories for alkaline HOR on the basis of diverse activity descriptors, i.e ., hydrogen binding energy theory and bifunctional theory. The design principles and recent advances of HOR catalysts employing the aforementioned theories are then summarized. Next, the strategies and recent progress in improving the antioxidation capability of HOR catalysts, a thorny issue which has not received sufficient attention, are discussed. Moreover, the significance of correlating computational models with real catalyst structure and the electrode/electrolyte interface is further emphasized. Lastly, the remaining controversies about the alkaline HOR mechanisms as well as the challenges and possible research directions in this field are presented.

• This review provides the basics of fuel cells, O 2 , MN 4 -macrocycles, M-O 2 bond and ORR. • Summary of MN 4 -macrocycles based nanocomposites for ORR with activity and stability. • List activity descriptors for MN 4 -macrocycles with their theoretical clarifications. • The difficulties and future aspects of MN 4 - macrocycles for fuel cell applications. The oxygen reduction response (ORR) shows sluggish kinetics on cathode surface, which welcomes a noteworthy commitment to the efficiency loss of the fuel cell devices. The advancements in the designing and developments of the competent electrocatalysts for ORR suggest that the macrocycles is the class of versatile materials for the rapid ORR. The hypothetical investigations and trial results specify that the ORR activity of MN 4 -macrocycles (M = Mn, Fe and Co) can be regulated by directing its MII/III formal potential through proper substitution on the macrocyclic framework and metal center. In this work, we tended to the principal dialog beginning from the fundamental chemistry of fuel cell, ORR, macrocycles, dioxygen, and metal–dioxygen (M–O 2) bond communication, as the establishment of this survey. At that point, the emphasis on the comprehensive designs and developments on current macrocycles-based nanocomposites for ORR and the molecular understanding of macrocycles-based ORR descriptors, was considered as the core of this survey. The significance of this survey lies in objective planning the electrocatalysts beginning from the most essential normal for the electronic auxiliary designing to an increasingly reasonable dimension of nanofabrication. [ABSTRACT FROM AUTHOR]