Abstract
Atomic interface regulation is thought to be an efficient method to adjust the performance of single atom catalysts. Herein, a practical strategy was reported to rationally design single ...copper atoms coordinated with both sulfur and nitrogen atoms in metal-organic framework derived hierarchically porous carbon (S-Cu-ISA/SNC). The atomic interface configuration of the copper site in S-Cu-ISA/SNC is detected to be an unsymmetrically arranged Cu-S
1
N
3
moiety. The catalyst exhibits excellent oxygen reduction reaction activity with a half-wave potential of 0.918 V vs. RHE. Additionally, through in situ X-ray absorption fine structure tests, we discover that the low-valent Cuprous-S
1
N
3
moiety acts as an active center during the oxygen reduction process. Our discovery provides a universal scheme for the controllable synthesis and performance regulation of single metal atom catalysts toward energy applications.
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•The up-to-date reports with respect to the chemical synthesis of SAA are overviewed.•The significance of SAA for representative electrochemical and heterogeneous catalytic reactions ...is analyzed.•The major challenges and opportunities pertaining to this cutting-edge field are suggested.
The development of low-cost, high-performance catalysts at the atomic level has become a challenging issue for large-scale applications of renewable clean energy technologies. Atomic sites catalysts, such as single atoms catalysts (SAC), single clusters catalysts (SCC), single-atom alloys (SAA), have proved their performance in various catalytic reactions due to their extremely high atom utilization efficiency, unique structure, and exceptional catalytic selectivity. A deep understanding and design of the active center of the catalyst at the atomic level has become a top priority for current research. Compared with SAC and SCC, SAA has its own uniqueness. In this review, we focused on the recent progress on the preparation methods of SAA and discussed the key factors controlling the structure of SAA. In addition, several important catalytic reactions performed over well-defined SAA are analyzed. Finally, the challenges and the perspectives of this cutting-edge field are suggested. We believe that this critical review provides a guidance for the rational design of SAA for catalytic applications.
Modulating the surface and spatial structure of the host is associated with the reactivity of the active site, and also enhances the mass transfer effect of the CO2 electroreduction process (CO2RR). ...Herein, we describe the development of two‐step ligand etch–pyrolysis to access an asymmetric dual‐atomic‐site catalyst (DASC) composed of a yolk–shell carbon framework (Zn1Mn1‐SNC) derived from S,N‐coordinated Zn−Mn dimers anchored on a metal–organic framework (MOF). In Zn1Mn1‐SNC, the electronic effects of the S/N−Zn−Mn−S/N configuration are tailored by strong interactions between Zn−Mn dual sites and co‐coordination with S/N atoms, rendering structural stability and atomic distribution. In an H‐cell, the Zn1Mn1‐SNC DASC shows a low onset overpotential of 50 mV and high CO Faraday efficiency of 97 % with a low applied overpotential of 343 mV, thus outperforming counterparts, and in a flow cell, it also reaches a high current density of 500 mA cm−2 at −0.85 V, benefitting from the high structure accessibility and active dual sites. DFT simulations showed that the S,N‐coordinated Zn−Mn diatomic site with optimal adsorption strength of COOH* lowers the reaction energy barrier, thus boosting the intrinsic CO2RR activity on DASC. The structure‐property correlation found in this study suggests new ideas for the development of highly accessible atomic catalysts.
The highly accessible yolk–shell structure and tailored electronic effects of the dual‐atomic‐site catalyst (DASC) Zn1Mn1‐SNC endow it with excellent performance in the conversion of CO2 into CO in both an H‐cell and a flow cell. Robust interactions with the Zn−Mn dual site, which shows an ideal adsorption strength for COOH*, effectively decrease the energy barrier of the reaction, thereby enhancing the inherent activity of CO2 reduction on the DASC.
Oxygen-involved electrochemical reactions are crucial for plenty of energy conversion techniques. Herein, we rationally designed a carbon-based Mn–N2C2 bifunctional electrocatalyst. It exhibits a ...half-wave potential of 0.915 V versus reversible hydrogen electrode for oxygen reduction reaction (ORR), and the overpotential is 350 mV at 10 mA cm–2 during oxygen evolution reaction (OER) in alkaline condition. Furthermore, by means of operando X-ray absorption fine structure measurements, we reveal that the bond-length-extended Mn2+–N2C2 atomic interface sites act as active centers during the ORR process, while the bond-length-shortened high-valence Mn4+–N2C2 moieties serve as the catalytic sites for OER, which is consistent with the density functional theory results. The atomic and electronic synergistic effects for the isolated Mn sites and the carbon support play a critical role to promote the oxygen-involved catalytic performance, by regulating the reaction free energy of intermediate adsorption. Our results give an atomic interface strategy for nonprecious bifunctional single-atom electrocatalysts.
Designing highly active and robust platinum-free catalysts for hydrogen evolution reaction is of vital importance for clean energy applications yet challenging. Here we report highly active and ...stable cobalt-substituted ruthenium nanosheets for hydrogen evolution, in which cobalt atoms are isolated in ruthenium lattice as revealed by aberration-corrected high-resolution transmission electron microscopy and X-ray absorption fine structure measurement. Impressively, the cobalt-substituted ruthenium nanosheets only need an extremely low overpotential of 13 mV to achieve a current density of 10 mA cm
in 1 M KOH media and an ultralow Tafel slope of 29 mV dec
, which exhibit top-level catalytic activity among all reported platinum-free electrocatalysts. The theoretical calculations reveal that the energy barrier of water dissociation can greatly reduce after single cobalt atom substitution, leading to its superior hydrogen evolution performance. This study provides a new insight into the development of highly efficient platinum-free hydrogen evolution catalysts.
Single-atom catalysts (SACs), distinguished by their exceptional atomic efficiency and modifiable coordination structures, find wide-ranging applicability, notably in the context of the hydrogen ...evolution reaction (HER). Herein, we synthesized a Ti3C2Tx-based Ni single-atom catalyst (Ni SA@N-Ti3C2Tx) by immersing a single Ni atom into the Ti vacancies of Ti3C2Tx and using a N-doping strategy. X-Ray adsorption fine structure revealed the formation of local Ni-N1C1 and an unsaturated C–Ni–N bridge configuration for isolated Ni species. Moreover, Ni SA@N-Ti3C2Tx exhibited an excellent HER performance with an overpotential of 63 mV at 10 mV cm−2. This work could enable use of MXene-based SACs in the HER.
The phase of nanocrystals has a key role in the modulation of catalytic properties. Uniform and well‐crystallized nickel phosphide nanocrystals with controlled phases (Ni5P4, Ni2P, and Ni12P5) and ...narrow size distributions are synthesized by a wet chemical method. The phases of the as‐synthesized nickel phosphide nanocrystals are controlled by the P/Ni precursor molar ratio, heating process, and time of reaction. Rarely reported nearly monodisperse 5.6 nm Ni5P4 nanocrystals are successfully synthesized and show superior hydrogen evolution reaction (HER) activity. Only a low overpotential of 103 mV is required to achieve the HER current of 10 mA cm−2 at a low catalyst loading of 0.12 mg cm−2. The high HER activity is attributed to the high quality of the as‐obtained Ni5P4 nanocrystals, which have the electronic effect from the Ni5P4 phase and also high surface area owing to the small particle size. A systematic study of the controlled synthesis of nickel phosphide nanocrystals is shown in this paper, and the HER catalytic activity is improved through the phase‐ and size‐controlled synthesis of nanocrystals.
Nickel phosphide nanocrystals: High‐quality nickel phosphide nanocrystals with controlled phases (Ni5P4, Ni2P, and Ni12P5) and narrow size distributions are synthesized. The rarely reported nearly monodisperse 5.6 nm Ni5P4 nanocrystals show superior hydrogen evolution reaction (HER) activity.
The electrochemical CO2 reduction reaction (CO2RR) is of importance for reducing global CO2 emissions. Herein, we reported a highly active CO2RR catalyst, namely Co–N–Ni/NPCNSs, which is considered ...as an advanced single-site catalyst with Co–N–Ni bimetallic sites connected by a N bridge between Co and Ni. The N-bridged Co–N–Ni bimetallic sites were confirmed by the X-ray absorption spectroscopy. The Co–N–Ni/NPCNSs catalyst shows a higher turnover frequency of 2049 h−1 at a low overpotential of 370 mV and CO faradaic efficiency of 96.4% compared to that of Co–N/NPCNSs (1205 h−1 and 61.5%) and Ni–N/NPCNSs (404 h−1 and 45.0%) with single Co–N4 and Ni–N4 sites, respectively. In situ synchrotron radiation Fourier transform infrared spectra and DFT calculations show that N-bridged Co–N–Ni bimetallic sites promote the formation of COOH* intermediates, thus accelerating CO2RR.
For electrocatalytic reduction of CO
2
to CO, the stabilization of intermediate COOH* and the desorption of CO* are two key steps. Pd can easily stabilize COOH*, whereas the strong CO* binding to Pd ...surface results in severe poisoning, thus lowering catalytic activity and stability for CO
2
reduction. On Ag surface, CO* desorbs readily, while COOH* requires a relatively high formation energy, leading to a high overpotential. In light of the above issues, we successfully designed the PdAg bimetallic catalyst to circumvent the drawbacks of sole Pd and Ag. The PdAg catalyst with Ag-terminated surface not only shows a much lower overpotential (-0.55 V with CO current density of 1 mA/cm
2
) than Ag (−0.76 V), but also delivers a CO/H
2
ratio 18 times as high as that for Pd at the potential of -0.75 V vs. RHE. The issue of CO poisoning is significantly alleviated on Ag-terminated PdAg surface, with the stability well retained after 4 h electrolysis at -0.75 V vs. RHE. Density functional theory (DFT) calculations reveal that the Ag-terminated PdAg surface features a lowered formation energy for COOH* and weakened adsorption for CO*, which both contribute to the enhanced performance for CO
2
reduction.
Mesoporous Fe, S, N doped carbon (m-FeSNC) materials have been successfully synthesized by pyrolysis of polymerized o-phenylenediamine using binary initiators. It exhibited high electrocatalytic ...activity towards oxygen reduction reaction, and zinc-air battery with higher performance has been fabricated using m-FeSNC than using commercial Pt/C.
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