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Regulating the coordination environment of transition-metal based materials in the axial direction with heteroatoms has shown great potential in boosting the oxygen reduction reaction (ORR). The coordination configuration and the regulation method are pivotal and elusive. Here, we report a combined strategy of matrix-activization and controlled-induction to modify the CoN4 site by axial coordination of Co—S (Co1N4-S1), which was validated by the aberration-corrected electron microscopy and X-ray absorption fine structure analysis. The optimal Co1N4-S1 exhibits an excellent alkaline ORR activity, according to the half-wave potential (0.897 V vs. reversible hydrogen electrode (RHE)), Tafel slope (24.67 mV/dec), and kinetic current density. Moreover, the Co1N4-S1 based Zn-air battery displays a high power density of 187.55 mW/cm2 and an outstanding charge—discharge cycling stability for 160 h, demonstrating the promising application potential. Theoretical calculations indicate that the better regulation of CoN4 on electronic structure and thus the highly efficient ORR performance can be achieved by axial Co—S. [ABSTRACT FROM AUTHOR]

Dual-active sites (DASs) catalysts have positive potential applications in broad fields because of their specific active sites and synergistic catalytic effects. Therefore, the controllable synthesis and finely regulating the activity of such catalysts has become a hot research area for now. In this work, we developed a pyrolysis-etching-hydrogen activation strategy to prepare the DASs catalysts involving single-atom Cu and B on N-doped porous carbon material (Cu1-B/NPC). Numerous systematic characterization and density functional theoretical (DFT) calculation results showed that the Cu and B existed as Cu-N4 porphyrin-like unit and B-N3 unit in the obtained catalyst. DFT calculations further revealed that single-atom Cu and B sites were linked by bridging N atoms to form the Cu1-B-N6 dual-sites. The Cu1-B/NPC catalyst was more effective than the single-active site catalysts with B-N3 sites in NPC (B/NPC) and Cu-N4 porphyrin-like sites in NPC (Cu1/NPC), respectively, for the dehydrogenative coupling of dimethylphenylsilane (DiMPSH) with various alcohols, performing the great activity (> 99%) and selectivity (> 99%). The catalytic performances of the Cu1-B/NPC catalyst remained nearly unchanged after five cycles, also indicating its outstanding recyclability. DFT calculations showed that the Cu1-B-N6 dual-sites exhibited the lowest energy profile on the potential energy surface than that of sole B-N3 and Cu-N4 porphyrin-like sites. Furthermore, the rate-limiting step of dehydrogenation of DiMPSH on Cu1-B-N6 dual-sites also showed a much lower activation energy than the other two single sites. Benefitting from the superiority of the Cu1-B-N6 dual-sites, the Cu1-B/NPC catalyst can also be used for CO2 electroreduction to produce syngas. Thus, DASs catalysts are promising to achieve multifunctional catalytic properties and have aroused positive attention in the field of catalysis. [ABSTRACT FROM AUTHOR]

Efficient electroreduction of CO2 into CO and other chemicals turns greenhouse gases into fuels and value-added chemicals, holding great promise for a closed carbon cycle and the alleviation of climate changes. However, there are still challenges in the large-scale application of CO2 electroreduction due to the sluggish kinetics. Herein we develop a self-assembly strategy to synthesize a highly efficient CO2 reduction electrocatalyst with atomically dispersed Ni-N4 active centers anchored on polymer-derived mesh-like N-doped carbon nanofibers (Ni-N4/NC). The Ni-N4/NC exhibits high selectivity for CO2 reduction reaction with CO Faradaic efficiency (CO FE) above 90% over a wide potential range from −0.6 to −1.0 V vs. RHE. The catalyst reaches a maximum CO FE up to 98.4% at −0.8 V with a TOF of 1.28 × 105 h−1 and Tafel slope of 113 mV·dec−1. The catalyst also exhibits remarkable stability, with little change in current density and CO FE over a 10-hour durability test at −0.8 V vs. RHE. This method provides a new route for the synthesis of highly efficient CO2 reduction electrocatalyst. [ABSTRACT FROM AUTHOR]

In the field of electrolysis of water, the design and synthesis of catalysts over a wide pH range have attracted extensive attentions. In this paper, Co and N are co-introduced into the structural unit of tungsten disulfide (WS2), and the hydrogen evolution reaction (HER) performances of different WS2-based catalysts are theoretically predicted and systematically studied by density functional theory (DFT) calculations. With the guidance of DFT calculations, an evaporation-pyrolysis strategy is applied to prepare Co and N co-doped WS2 (Co,N-WS2) flower-like nanosheets, which exhibits excellent HER performance over a wide pH range. In addition, the DFT calculations show that the active sites in Co,N-WS2 have a good ability of hydrogen adsorption after the introduction of Co and N, suggesting that such a co-doping system will be an ideal catalyst for oxidative dehydrogenation (ODH). The following experiment results indeed evidence that the Co,N-WS2 catalyst displays a high activity in the ODH of 1,2,3,4-tetrahydroquinoline (4H-quinoline) and its derivatives. Therefore, this work provides a good example for the rational design and accurate preparation of functional catalysts, which enables it possible to develop other efficient catalysts with multiple functions. [ABSTRACT FROM AUTHOR]

Large scale synthesis of high-efficiency bifunctional electrocatalyst based on cost-effective and earth-abundant transition metal for overall water splitting in the alkaline environment is indispensable for renewable energy conversion. In this regard, meticulous design of active sites and probing their catalytic mechanism on both cathode and anode with different reaction environment at molecular-scale are vitally necessary. Herein, a coordination environment inheriting strategy is presented for designing low-coordination Ni2+ octahedra (L-Ni-8) atomic interface at a high concentration (4.6 at.%). Advanced spectroscopic techniques and theoretical calculations reveal that the self-matching electron delocalization and localization state at L-Ni-8 atomic interface enable an ideal reaction environment at both cathode and anode. To improve the efficiency of using the self-modification reaction environment at L-Ni-8, all of the structural features, including high atom economy, mass transfer, and electron transfer, are integrated together from atomic-scale to macro-scale. At high current density of 500 mA/cm2, the samples synthesized at gram-scale can deliver low hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) overpotentials of 262 and 348 mV, respectively. [ABSTRACT FROM AUTHOR]

We developed a strategy based on coordination polymer to synthesize singleatom site Fe/N and S-codoped hierarchical porous carbon (Fe1/N,S-PC). The as-obtained Fe1/N,S-PC exhibited superior oxygen reduction reaction (ORR) performance with a half-wave potential (E1/2, 0.904 V vs. RHE) that was better than that of commercial Pt/C (E1/2, 0.86 V vs. RHE), single-atom site Fe/N-doped hierarchical porous carbon (Fe1/N-PC) without S-doped (E1/2, 0.85 V vs. RHE), and many other nonprecious metal catalysts in alkaline medium. Moreover, the Fe1/N,S-PC revealed high methanol tolerance and firm stability. The excellent electrocatalytic activity of Fe1/N,S-PC is attributed to the synergistic effects from the atomically dispersed porphyrin-like Fe-N4 active sites, the heteroatom codoping (N and S), and the hierarchical porous structure in the carbon materials. The calculation based on density functional theory further indicates that the catalytic performance of Fe1/N,S-PC is better than that of Fe1/N-PC owing to the sulfur doping that yielded different rate-determining steps. [ABSTRACT FROM AUTHOR]