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Single-atom catalysts (SACs) based on metal–nitrogen–carbon (M–N–C) compounds have been identified as a potential substitute for Pt-based oxygen reduction reaction (ORR) catalysts due to their facile availability and low cost. M1M2–N–C based dual-atom catalysts (DACs) may be utilised to regulate the active site and optimise their ORR activity. Accordingly, M1M2–N6–C14 (M1 = Mn, Fe, Co; M2 = late transition metals) DACs were constructed within a graphene slab. M1M2–N–C is more stable than the corresponding M1–N–C and M2–N–C due to the affinity between M1 and M2. Furthermore, the ORR activity of FeM–N–C (M = late transition metals), MnM–N–C (Co, Ru, Rh, Os, Ir, and Re) and CoM–N–C (M = Cu, Zn, Pd, and Pt) is enhanced in comparison to that of Fe–N–C, due to the modified electronic properties. In comparison to other active ORR electrocatalysts, FeCu–N–C is positioned at a relatively high level on the volcano plot. To gain further insight into the dynamic stability of FeCu–N–C under working conditions (*OOH, 80 °C), an ab initio molecular dynamics simulation was employed. The accelerated structural evolution of the FeCu–N–C electrocatalyst resulted in the Cu atom being pulled out of the N–C substrate plane. Nevertheless, the resulting Fe(vacancy)–N–C and Fe(vacancy)–NH–C electrocatalysts have been observed to retain high ORR activity and stability. The findings of this study have significant implications for the design of DACs. [ABSTRACT FROM AUTHOR]

The electrochemical decomposition of water plays a critical role in green and sustainable energy. However, the development of efficient and low-cost non-noble metal catalysts to overcome the high potential of the anodic oxygen evolution reaction (OER) is still challenging. In this work, electrocatalysts with high OER activity were obtained by doping Co/Fe bimetals into Ni3S2 (CF-NS) via a simple single-step hydrothermal method by adjusting the doping ratio of bimetals. A series of characterization studies revealed that the introduction of a Co/Fe co-dopant increased the number of active sites and improved the electroconductibility, while optimizing the electronic structure of Ni3S2. Meanwhile, Fe-induced high valence Ni contributed to the production of an OER active phase NiOOH. The unique dendritic crystal morphology facilitated the disclosure of the active sites and the expansion of mass transfer channels. The optimized sample required a low overpotential of 146 mV to obtain a current density of 10 mA cm−2 in 1.0 M KOH solution. The optimized sample also operated stably for at least 86 h. In sum, the proposed method looks very promising for designing efficient, stable, and low-cost non-precious metal catalysts with high conductivity and multiple active sites, useful for future synthesis of transition metal sulfide catalysts. [ABSTRACT FROM AUTHOR]

Iron‐nitrogen‐doped carbon (Fe‐NC) is an ideal candidate to replace Pt‐based oxygen reduction reaction (ORR) electrocatalysts due to its low cost and comparably high intrinsic activity. To further enhance the ORR performance of Fe‐NC electrocatalysts, efforts have been focused on two main methods. One is to enhance the intrinsic activity of FeNx sites through electronic and geometric regulation, and the other is to increase the density of active sites by introducing high‐nitrogen‐containing precursors or co‐doping methods. Herein, we report a strategy to further increase the Fe loading through the introduction of a trace amount of Cu atoms. Significant enhancement of the electrocatalytic ORR property is observed in the as‐prepared Fe and Cu co‐doped electrocatalyst with superior half‐wave potential (E1/2) in both alkaline and acid electrolyte. Experimental and theoretical study reveals that the introduction of a trace amount of Cu atoms is beneficial for the formation of FeN4 sites, owing to the reduced formation energy. This work opens up a wide avenue to further increase the Fe loading in Fe‐NC electrocatalysts through bimetal co‐doping method. [ABSTRACT FROM AUTHOR]

The strain effect on oxygen reduction reaction (ORR) activity and stability of FeNC electrocatalysts has been studied using density functional theory in this work. Based on the reaction free energy results, the rate-determining step (RDS) of ORR on FeNC is *OH → H2O, and the reaction proceeds with the pathway O2 → *OOH → *O → *OH → H2O on the Fe site. Tensile stress is favorable to enhance the ORR activity, and the highest ORR activity is obtained on the 6%-FeNC electrocatalyst. On the other hand, when the whole oxygen reduction process needs synergy between Fe and adjacent C atoms and proceeds with the pathway O2 → *OOH → *TS → *O & #OH → *O → *OH → H2O, the applied stress will decrease the ORR activity of the FeNC electrocatalyst. We further constructed a Cu@FeNC core–shell model to simulate strained FeNC. However, the adsorption energy of ORR intermediates on Cu@FeNC (1.9%-FeNC) is much weaker than on the corresponding 2%-FeNC, mainly due to the coordination between the Cu substrate and Fe atom. In addition, the formation energy and binding energy indicate that neither tensile nor compressive stress is conducive to the stability of the FeNC electrocatalyst. In summary, tensile stress could enhance the ORR activity of FeNC electrocatalysts when ORR occurs on the Fe atom only. What's more, we should pay more attention to the influence of interface interaction if utilizing a M@FeNC model to achieve strained FeNC. [ABSTRACT FROM AUTHOR]

Preparation and study of FeOOH modified Co 9 S 8 composites were successful. The catalysts have abundant non-homogeneous interfaces between FeOOH and Co 9 S 8 nanosheets, which optimize the coordination environments of Fe and Co sites through the redistribution of interfacial charges. This results in appropriate chemisorption strength of oxygenated intermediates, leading to accelerated reaction kinetics, abundant active sites, and good OER properties. [Display omitted] • The FeOOH/Co 9 S 8 composites electrocatalyst was developed. • The redistribution of interface charges optimizes the coordination environment of Fe and Co sites. • Appropriate chemisorption strength of oxygenated intermediates. Efficient oxygen evolution reaction (OER) is vital for water electrolysis and advanced hydrogen energy production. However, the sluggish kinetics of this reaction require significant overpotentials, leading to high energy consumption. Therefore, developing OER electrocatalysts with exceptional performance and long-term durability is crucial for enhancing the energy efficiency and cost-effectiveness of the hydrogen production process. In this research, novel FeOOH/Co 9 S 8 catalysts were prepared through a two-step hydrothermal reaction followed by one-step electrodeposition on nickel foam for an alkaline OER. The as-obtained catalysts possessed abundant non-homogeneous interfaces between FeOOH and Co 9 S 8 nanosheets, conducive to optimized coordination environments of Fe and Co sites by redistributing interfacial charges. This synergy strengthened the chemisorption of oxygenated intermediates, leading to accelerated reaction kinetics, abundant active sites, and enhanced OER performance. The optimized electrocatalyst FeOOH/Co 9 S 8 -15 achieved a current density of 10 mA cm-2 at an overpotential of 248 mV and good stability for over 140 h. This study presents a novel approach for producing compelling and durable alkaline dielectric OER electrocatalysts, which will be helpful in the future manufacturing of advanced energy devices. [ABSTRACT FROM AUTHOR]

The Front Cover picture is inspired by the principle demonstrated in the fascinating Sagrada Família Basilica (Barcelona, Spain), where sunlight streaming through the windows reveals the beauty of its stained‐glass windows. Similarly, in this work, thermal activation of the chemically inert amorphous carbon−nitrogen reveals its extraordinary oxygen reduction reaction activity! More information can be found in the Communication by W. Zhang, W. Zheng, and co‐workers on page 1269 in Issue 6, 2017 (DOI: 10.1002/celc.201700106). [ABSTRACT FROM AUTHOR]

[Display omitted] • The effect of structure evolution under working condition of MNC electrocatalysts on the OER activity and stability has been studied with the DFT method. • This work conducted a comprehensive evaluation method for MNC electrocatalysts by taking ΔG *OH as the screening criterion for OER activity and ΔE b of electrocatalysts under working conditions as the stability descriptor. • The stability of MNC electrocatalysts under working conditions, including high temperature, dynamic condition, local electric field and strong specific adsorption has been studied in detail. Developing low-cost, high activity and stability oxygen evolution reaction (OER) catalysts is significantly important but still challenging for water electrolyzers. In this work, we calculated the OER activity and stability of Metal-Nitrogen-Carbon (MNC, M = Co, Ru, Rh, Pd, Ir) based electrocatalyst with different structures (MN 4 C 8 , MN 4 C 10 , MN 4 C 12) using density functional theory (DFT) method. These electrocatalysts were divided into three groups based on the value of ΔG *OH , that is ΔG *OH > 1.53 eV (PdN 4 C 8 , PdN 4 C 10 , PdN 4 C 12), ΔG *OH < 1.23 eV (RuN 4 C 8 , RuN 4 C 10 , RuN 4 C 12 , CoN 4 C 8 , CoN 4 C 10) and 1.23 eV < ΔG *OH < 1.53 eV (RhN 4 C 8 , RhN 4 C 10 , RhN 4 C 12 , IrN 4 C 8 , IrN 4 C 10 , IrN 4 C 12 , CoN 4 C 12), and ΔG *OH determine whether the structure evolution will appear. The results proved that MNC (M = Rh, Ir) with 1.23 eV < ΔG *OH < 1.53 eV shows higher OER activity due to moderate binding energy between reaction intermediates and MNC. Furthermore, these catalysts could maintain M N C structure without further oxidation and structural evolution under working conditions (high temperature, dynamic condition, local electric field and strong specific adsorption), therefore show excellent stability. However, MNC electrocatalyst with ΔG *OH > 1.53 eV or ΔG *OH < 1.23 eV revealed less stability under working conditions, due to their low intrinsic stability or structural evolution under working conditions, respectively. In conclusion, we proposed a comprehensive evaluation method for MNC electrocatalysts by taking ΔG *OH as the screening criterion for OER activity and stability, as well as ΔE b under working condition as descriptor of stability. This is of great significance for the design and screening of ORR, OER and HER electrocatalysts under working conditions. [ABSTRACT FROM AUTHOR]

[Display omitted] • Study of crystal plane, strain and ligand effects on the intrinsic stability of Pt alloy electrocatalysts. • Study of specific adsorption and local electric field on the stability of Pt alloy electrocatalysts. • Highlighting the importance of intrinsic stability and working environment on the durability of Pt alloy electrocatalysts. Electrocatalyst stability is a key parameter for commercializing high-temperature polymer electrolyte membrane fuel cells (HT-PEMFCs). Here, we used density functional theory (DFT) to investigate the stability of Pt-based electrocatalysts by calculating the binding energy (ΔE b) of surface Pt atoms under working conditions. Our results show that Pt(1 1 1) is more stable than Pt(1 0 0) and Pt(1 1 0) under vacuum conditions. Stress hurts the stability of Pt(1 1 1), regardless of compressive or tensile stress. Most of the transition metals alloyed with Pt improve the stability of Pt(1 1 1), especially PtV, PtY, and PtTa, which increase the ΔE b by 0.60–0.70 eV (ΔΔE b). However, the stability of Pt is significantly destroyed under the working conditions of oxygen reduction reaction (ORR). The specific adsorption of ORR intermediates and electrolyte ions decreases the ΔE b of Pt(1 1 1) by 0.35–0.95 eV, and the effect of PO 4 3-* is more significant. Furthermore, when the electric field of the electrochemical double layer is coupled with PO 4 3-* specific adsorption, ΔΔE b further increases to 1.12 eV. Our results highlight the importance of the intrinsic ΔE b and the working conditions for the stability of Pt-based electrocatalysts. This work provides important guidelines for the design of stable ORR electrocatalysts for HT-PEMFCs. [ABSTRACT FROM AUTHOR]

[Display omitted] • Design of the prior PA-resistance electrocatalysts through theoretical calculation. • Discovery of different scaling relationship of the adsorption energy difference of O 2 and H x PO(3-x)- 4 on Pt 3 M(1 1 1) alloy surface. • Pt X Cu as the object for the research of internal mechanism of the potentially high PA resistance property. • Higher PA-resistance performance of Pt 2 Cu compared to the commercial PtC in half-cell and full-cell tests. In high temperature polymer electrolyte membrane fuel cells (HT-PEMFCs), dissociative H 3 PO 4 in cathode will block the active sites of Pt-based electrocatalyst, which thus failure to catalyze the oxygen reduction reaction (ORR). Therefore, the electrocatalysts for the ORR in HT-PEMFCs with high resistance to H 3 PO 4 poisoning are significantly important. Due to the similar bonding structure between H x PO 4 3-x/O 2 and Pt (Pt-O), the design of catalysts which could selectively reduce the adsorption energy of the H 3 PO 4 is urgently needed. In this work, we screen proper H 3 PO 4 resistance electrocatalysts through theoretical calculation based on the adsorption energy difference between H x PO 4 3-x and O 2 as an evaluation criterion. Then, we prepared a series of Pt x Cu catalysts based on the theoretical calculation results and further studied the structure-performance relationship of phosphoric acid-resistant catalysts through combining physical property characterization and electrochemical tests including half-cell and single-cell. The mass activity of Pt 2 Cu/C is 0.51 A/mg Pt , exceeding the DOE's 2020 target of 0.44 A/mg Pt. After add 0.1 M H 3 PO 4 into the HClO 4 electrolyte, the half-wave potential (E 1/2) of Pt 2 Cu/C is only negatively shifted by 47 mV, much lower than 90 mV of TKK Pt/C. Furthermore, the HT-PEMFC with Pt 2 Cu/C in the cathode shows a peak power density of 383.4 mW/cm2, which surpasses that of TKK Pt/C for 231.0 mW/cm2. Our strategy of screening catalysts based on the adsorption energy difference study and further verified by experimental methods provides a promising strategy for the design of practical electrocatalyst in the cathode of HT-PEMFCs. [ABSTRACT FROM AUTHOR]

Highlighting sentence: Fe-Ni heterostructure is synergistically beneficial to overall water splitting on the (1 1 0) fact of pentlandite. [Display omitted] • Bimetallic Fe-Ni can synergistically catalyze HER and OER, respectively. • The OER catalytic activity can be improved by anions-poisonous adsorption. • The mechanism of pentlandite for water splitting is uncovered at atomic level. Developing stable, low cost, and efficient HER/OER bifunctional electrocatalysts is highly desired in overall water splitting. The bimetallic Fe-Ni-based systems can exhibit a great potential for overall water splitting. However, its electrocatalytic mechanism remain elusive as a bifunctional catalyst. Herein, in acidic medium, HER and OER mechanisms on the (1 1 0) facet of pentlandite are systematically investigated by means of density functional theory. The results unravel that the bimetallic Fe-Ni heterostructure can delicately regulate the charge transfer to accommodate themselves separately to oxidation and reduction. The Fe site exhibits the excellent catalytic HER activity while the Ni site shows the high catalytic OER activity. Interestingly, during the OER process, the Fe site with *OH-poisonous adsorption can further optimize catalytic performance of its adjacent Ni site. These studies provide an in-depth understanding in the synergistic effect of Fe-Ni toward rational design and fabrication of efficient water splitting electrocatalysts. [ABSTRACT FROM AUTHOR]

Fe 5 Ni 4 S 8 /Ni 3 S 2 is a highly efficient and robust bifunctional electrocatalyst for overall water splitting due to its charge transport double-channel structure and strong electronic interaction. [Display omitted] • The stepped rod-shaped Ni 3 S 2 3D nanoarray structure supplied the system with sufficient active sites. • The double-channel structure, which consisted of high-conductivity Fe 5 Ni 4 S 8 and NF, provided an increase in the rate of internal charge transfer. • The overall water splitting device with appropriate samples achieved 1.64 V@10 mA cm−2 cell voltage. And it remained active for at least 120 h at an industrial-grade high current density (500 mA cm−2). Overall water splitting technology is critical for the future of a clean and sustainable hydrogen energy infrastructure. Ni 3 S 2 (NS) is considered a good performing oxygen evolution reaction (OER) catalyst, but exhibits unsatisfactory hydrogen evolution reaction (HER) activity. In this study, Fe 5 Ni 4 S 8 (FNS) material was incorporated into an NS nanoarray, generating a low-cost, efficient, and stable bifunctional FNS/NS heterostructure for electrolyzed water catalysts. The hydrophilicity of pretreated FNS was quite high, whereas the stepped rod-shaped NS structure had a large number of radial active sites. Additionally, the high-conductivity of FNS and nickel foam (NF) provided a double-channel structure for rapid internal charge transfer. The interconnecting a network of FNS, rod-shaped NS nanoarray, and NF substrate enabled one to accomplish a synergistic effect of enhanced kinetics and activity of OER, HER, and overall water splitting. To achieve a current density of 10 mA cm−2 in 1.0 M KOH solution, only overpotentials of 248 and 94 mV were required. Moreover, the voltage of the constructed FNS/NS||FNS/NS double-electrode battery system was only 1.64 V@10 mA cm−2, but the battery could have run for at least 120 h at an industrial current density of 500 mA cm−2. Therefore, this study offers a rational design of heterostructures as bifunctional electrocatalysts for overall water splitting. [ABSTRACT FROM AUTHOR]