Efficient, durable and inexpensive electrocatalysts that accelerate sluggish oxygen reduction reaction kinetics and achieve high-performance are highly desirable. Here we develop a strategy to ...fabricate a catalyst comprised of single iron atomic sites supported on a nitrogen, phosphorus and sulfur co-doped hollow carbon polyhedron from a metal-organic framework@polymer composite. The polymer-based coating facilitates the construction of a hollow structure via the Kirkendall effect and electronic modulation of an active metal center by long-range interaction with sulfur and phosphorus. Benefiting from structure functionalities and electronic control of a single-atom iron active center, the catalyst shows a remarkable performance with enhanced kinetics and activity for oxygen reduction in both alkaline and acid media. Moreover, the catalyst shows promise for substitution of expensive platinum to drive the cathodic oxygen reduction reaction in zinc-air batteries and hydrogen-air fuel cells.
Abstract
Non-noble transition metal oxides are abundant in nature. However, they are widely regarded as catalytically inert for hydrogen evolution reaction (HER) due to their scarce active electronic ...states near the Fermi-level. How to largely improve the HER activity of these kinds of materials remains a great challenge. Herein, as a proof-of-concept, we design a non-solvent strategy to achieve phosphate substitution and the subsequent crystal phase stabilization of metastable β-NiMoO
4
. Phosphate substitution is proved to be imperative for the stabilization and activation of β-NiMoO
4
, which can efficiently generate the active electronic states and promote the intrinsic HER activity. As a result, phosphate substituted β-NiMoO
4
exhibits the optimal hydrogen adsorption free energy (−0.046 eV) and ultralow overpotential of −23 mV at 10 mA cm
−2
in 1 M KOH for HER. Especially, it maintains long-term stability for 200 h at the large current density of 1000 mA cm
−2
with an overpotential of only −210 mV. This work provides a route for activating transition metal oxides for HER by stabilizing the metastable phase with abundant active electronic states.
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.
To meet the requirements of potential applications, it is of great importance to explore new catalysts for formic acid oxidation that have both ultra-high mass activity and CO resistance. Here, we ...successfully synthesize atomically dispersed Rh on N-doped carbon (SA-Rh/CN) and discover that SA-Rh/CN exhibits promising electrocatalytic properties for formic acid oxidation. The mass activity shows 28- and 67-fold enhancements compared with state-of-the-art Pd/C and Pt/C, respectively, despite the low activity of Rh/C. Interestingly, SA-Rh/CN exhibits greatly enhanced tolerance to CO poisoning, and Rh atoms in SA-Rh/CN resist sintering after long-term testing, resulting in excellent catalytic stability. Density functional theory calculations suggest that the formate route is more favourable on SA-Rh/CN. According to calculations, the high barrier to produce CO, together with the relatively unfavourable binding with CO, contribute to its CO tolerance.
Highlights
All the coordination engineering strategies, such as tuning the coordination species, the coordination number of the active centers, heteroatoms interactions within the support, synergetic ...interaction between neighboring metal monomers, and spatial microenvironment, have been summarized and discussed in detail.
Various single-atom catalysts (SACs) with different coordination spheres in energy conversion driven by thermal, light and electric energy have been systematically reviewed.
The current key challenges in SACs for energy conversion are pointed out, and some potential strategies/perspectives are proposed.
Reducing the dimensions of metallic nanoparticles to isolated, single atom has attracted considerable attention in heterogeneous catalysis, because it significantly improves atomic utilization and often leads to distinct catalytic performance. Through extensive research, it has been recognized that the local coordination environment of single atoms has an important influence on their electronic structures and catalytic behaviors. In this review, we summarize a series of representative systems of single-atom catalysts, discussing their preparation, characterization, and structure–property relationship, with an emphasis on the correlation between the coordination spheres of isolated reactive centers and their intrinsic catalytic activities. We also share our perspectives on the current challenges and future research promises in the development of single-atom catalysis. With this article, we aim to highlight the possibility of finely tuning the catalytic performances by engineering the coordination spheres of single-atom sites and provide new insights into the further development for this emerging research field.
Single-atom catalysts not only maximize metal atom efficiency, they also display properties that are considerably different to their more conventional nanoparticle equivalents, making them a ...promising family of materials to investigate. Herein we developed a general host-guest strategy to fabricate various metal single-atom catalysts on nitrogen-doped carbon (M
/CN, M = Pt, Ir, Pd, Ru, Mo, Ga, Cu, Ni, Mn). The iridium variant Ir
/CN electrocatalyses the formic acid oxidation reaction with a mass activity of 12.9 Formula: see text whereas an Ir/C nanoparticle catalyst is almost inert (~4.8 × 10
Formula: see text). The activity of Ir
/CN is also 16 and 19 times greater than those of Pd/C and Pt/C, respectively. Furthermore, Ir
/CN displays high tolerance to CO poisoning. First-principle density functional theory reveals that the properties of Ir
/CN stem from the spatial isolation of iridium sites and from the modified electronic structure of iridium with respect to a conventional nanoparticle catalyst.
The oxidation of hydrocarbons to produce high value-added compounds (ketones or alcohols) using oxygen in air as the only oxidant is an efficient synthetic strategy from both environmental and ...economic views. Herein, we successfully synthesized cobalt single atom site catalysts (Co SACs) with high metal loading of 23.58 wt.% supported on carbon nitride (CN), which showed excellent catalytic properties for oxidation of ethylbenzene in air. Moreover, Co SACs show a much higher turn-over frequency (19.6 h
−1
) than other reported non-noble catalysts under the same condition. Comparatively, the as-obtained nanosized or homogenous Co catalysts are inert to this reaction. Co SACs also exhibit high selectivity (97%) and stability (unchanged after five runs) in this reaction. DFT calculations reveal that Co SACs show a low energy barrier in the first elementary step and a high resistance to water, which result in the robust catalytic performance for this reaction.
Demonstrated here is the correlation between atomic configuration induced electronic density of single‐atom Co active sites and oxygen reduction reaction (ORR) performance by combining ...density‐functional theory (DFT) calculations and electrochemical analysis. Guided by DFT calculations, a MOF‐derived Co single‐atom catalyst with the optimal Co1‐N3PS active moiety incorporated in a hollow carbon polyhedron (Co1‐N3PS/HC) was designed and synthesized. Co1‐N3PS/HC exhibits outstanding alkaline ORR activity with a half‐wave potential of 0.920 V and superior ORR kinetics with record‐level kinetic current density and an ultralow Tafel slope of 31 mV dec−1, exceeding that of Pt/C and almost all non‐precious ORR electrocatalysts. In acidic media the ORR kinetics of Co1‐N3PS/HC still surpasses that of Pt/C. This work offers atomic‐level insight into the relationship between electronic density of the active site and catalytic properties, promoting rational design of efficient catalysts.
The correlation between atomic configuration induced electronic density of single‐atom Co active sites and oxygen reduction reaction (ORR) performance has been established by combining density‐functional theory calculations and electrochemical analysis. A metal–organic framework derived single‐atom Co catalyst, comprising an optimal Co1‐N3PS active moiety supported on hollow carbon polyhedron (Co1‐N3PS/HC), was synthesized, and it exhibits superior alkaline and acidic ORR performance.
The development of low‐cost, efficient, and stable electrocatalysts for the oxygen reduction reaction (ORR) is desirable but remains a great challenge. Herein, we made a highly reactive and stable ...isolated single‐atom Fe/N‐doped porous carbon (ISA Fe/CN) catalyst with Fe loading up to 2.16 wt %. The catalyst showed excellent ORR performance with a half‐wave potential (E1/2) of 0.900 V, which outperformed commercial Pt/C and most non‐precious‐metal catalysts reported to date. Besides exceptionally high kinetic current density (Jk) of 37.83 mV cm−2 at 0.85 V, it also had a good methanol tolerance and outstanding stability. Experiments demonstrated that maintaining the Fe as isolated atoms and incorporating nitrogen was essential to deliver the high performance. First principle calculations further attributed the high reactivity to the high efficiency of the single Fe atoms in transporting electrons to the adsorbed OH species.
Together alone: Anchored on N‐doped porous carbon via a cage‐encapsulated precursor pyrolysis strategy, isolated single iron atoms exhibit excellent oxygen reduction reaction (ORR) performance, good methanol tolerance, and outstanding stability. Control experiments and theoretical calculations demonstrate that the ORR performance results from the atomically dispersed iron.
Isolated single atomic site catalysts have attracted great interest due to their remarkable catalytic properties. Because of their high surface energy, single atoms are highly mobile and tend to form ...aggregate during synthetic and catalytic processes. Therefore, it is a significant challenge to fabricate isolated single atomic site catalysts with good stability. Herein, a gentle method to stabilize single atomic site metal by constructing defects on the surface of supports is presented. As a proof of concept, single atomic site Au supported on defective TiO2 nanosheets is prepared and it is discovered that (1) the surface defects on TiO2 nanosheets can effectively stabilize Au single atomic sites through forming the Ti–Au–Ti structure; and (2) the Ti–Au–Ti structure can also promote the catalytic properties through reducing the energy barrier and relieving the competitive adsorption on isolated Au atomic sites. It is believed that this work paves a way to design stable and active single atomic site catalysts on oxide supports.
Single atomic sites of Au are supported on defective TiO2 nanosheets and it is discovered that the surface defects on TiO2 nanosheets can effectively stabilize Au single atomic sites through forming a Ti–Au–Ti structure, and this Ti–Au–Ti structure can also promote the catalytic properties through reducing the energy barrier and relieving the competitive adsorption on isolated Au atomic sites.
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