Catalysts for hydrogen oxidation reaction (HOR) in alkaline electrolyte are important for anion exchange membrane fuel cells. Understanding the role of OH– during the HOR catalytic process in ...alkaline electrolyte is essential to design highly active HOR catalysts. Here, we attempt to isolate the influence of OH– by using surface-controlled Pt based nanoparticles as the model catalysts. With a comparison of the HOR activity between PtNi nanoparticles and acid washed PtNi nanoparticles, which have almost the same hydrogen binding energies but much different OH binding energies, it was found that the HOR activity in alkaline electrolyte is not mainly controlled by the OH adsorption. Therefore, a bifunctional catalyst promoting OH adsorption may not useful for HOR in alkaline electrolyte. Tuning the hydrogen binding energy was found to be an efficient way to enhance the HOR activity, and making Pt base alloy is a reasonable way to tune the hydrogen binding energies.
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.
Abstract
The development of cost-effective hydroxide exchange membrane fuel cells is limited by the lack of high-performance and low-cost anode hydrogen oxidation reaction catalysts. Here we report a ...Pt-free catalyst Ru
7
Ni
3
/C, which exhibits excellent hydrogen oxidation reaction activity in both rotating disk electrode and membrane electrode assembly measurements. The hydrogen oxidation reaction mass activity and specific activity of Ru
7
Ni
3
/C, as measured in rotating disk experiments, is about 21 and 25 times that of Pt/C, and 3 and 5 times that of PtRu/C, respectively. The hydroxide exchange membrane fuel cell with Ru
7
Ni
3
/C anode can deliver a high peak power density of 2.03 W cm
−2
in H
2
/O
2
and 1.23 W cm
−2
in H
2
/air (CO
2
-free) at 95 °C, surpassing that using PtRu/C anode catalyst, and good durability with less than 5% voltage loss over 100 h of operation. The weakened hydrogen binding of Ru by alloying with Ni and enhanced water adsorption by the presence of surface Ni oxides lead to the high hydrogen oxidation reaction activity of Ru
7
Ni
3
/C. By using the Ru
7
Ni
3
/C catalyst, the anode cost can be reduced by 85% of the current state-of-the-art PtRu/C, making it highly promising in economical hydroxide exchange membrane fuel cells.
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
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.
Fuel cells are the zero-emission automotive power source that best preserves the advantages of gasoline automobiles: low upfront cost, long driving range and fast refuelling. To make fuel-cell cars a ...reality, the US Department of Energy has set a fuel cell system cost target of US$30 kW
in the long-term, which equates to US$2,400 per vehicle, excluding several major powertrain components (in comparison, a basic, but complete, internal combustion engine system costs approximately US$3,000). To date, most research for automotive applications has focused on proton exchange membrane fuel cells (PEMFCs), because these systems have demonstrated the highest power density. Recently, however, an alternative technology, hydroxide exchange membrane fuel cells (HEMFCs), has gained significant attention, because of the possibility to use stable platinum-group-metal-free catalysts, with inherent, long-term cost advantages. In this Perspective, we discuss the cost profile of PEMFCs and the advantages offered by HEMFCs. In particular, we discuss catalyst development needs for HEMFCs and set catalyst activity targets to achieve performance parity with state-of-the-art automotive PEMFCs. Meeting these targets requires careful optimization of nanostructures to pack high surface areas into a small volume, while maintaining high area-specific activity and favourable pore-transport properties.
The design and synthesis of 3D covalent organic frameworks (COFs) have been considered a challenge, and the demonstrated applications of 3D COFs have so far been limited to gas adsorption. Herein we ...describe the design and synthesis of two new 3D microporous base‐functionalized COFs, termed BF‐COF‐1 and BF‐COF‐2, by the use of a tetrahedral alkyl amine, 1,3,5,7‐tetraaminoadamantane (TAA), combined with 1,3,5‐triformylbenzene (TFB) or triformylphloroglucinol (TFP). As catalysts, both BF‐COFs showed remarkable conversion (96 % for BF‐COF‐1 and 98 % for BF‐COF‐2), high size selectivity, and good recyclability in base‐catalyzed Knoevenagel condensation reactions. This study suggests that porous functionalized 3D COFs could be a promising new class of shape‐selective catalysts.
A nifty net: Two novel 3D microporous base‐functionalized COFs (BF‐COFs, see structure of one framework), were synthesized by the condensation of a tetrahedral alkyl amine with two planar triangular building units, and their catalytic properties were explored in the Knoevenagel condensation reaction. Both BF‐COFs showed excellent catalytic activity with high conversion, excellent size selectivity, and good recyclability.
Hollow nanomaterials have attracted a broad interest in multidisciplinary research due to their unique structure and preeminent properties. Owing to the high specific surface area, well‐defined ...active site, delimited void space, and tunable mass transfer rate, hollow nanostructures can serve as excellent catalysts, supports, and reactors for a variety of catalytic applications, including photocatalysis, electrocatalysis, heterogeneous catalysis, homogeneous catalysis, etc. Based on state‐of‐the‐art synthetic methods and characterization techniques, researchers focus on the purposeful functionalization of hollow nanomaterials for catalytic mechanism studies and intricate catalytic reactions. Herein, an overview of current reports with respect to the catalysis of functionalized hollow nanomaterials is given, and they are classified into five types of versatile strategies with a top‐down perspective, including textual and composition modification, encapsulation, multishelled construction, anchored single atomic site, and surface molecular engineering. In the detailed case studies, the design and construction of hierarchical hollow catalysts are discussed. Moreover, since hollow structure offers more than two types of spatial‐delimited sites, complicated catalytic reactions are elaborated. In summary, functionalized hollow nanomaterials provide an ideal model for the rational design and development of efficient catalysts.
Functionalization of hollow nanomaterials provides a versatile way for the rational design of hierarchical catalysts so as to achieve superior catalytic efficiency for a variety of catalytic applications, particularly for intricate reactions. Five types of functionalization strategies, i.e., geometric and composition modification, encapsulation, multishell construction, anchored single atomic sites, and surface molecular engineering, are overviewed and elaborated.
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.
Active nonprecious metal-based hydrogen evolution reaction (HER) electrocatalysts are critical for the clean and sustainable generation of hydrogen. Here, we synthesized multishelled FeCo@FeCoP@C ...hollow spheres by the carbonization and phosphorization of the FeCo-MIL-88 metal-organic framework. Owing to both composition (FeCo mixed phosphide) and morphology (multishelled morphology) effects, the as-obtained FeCo@FeCoP@C exhibits excellent HER performance with a low overpotential of 65 mV to achieve an HER current density of 10 mA cm–2 and high stability in acidic solution. Density functional theory calculations show that the FeCoP have the optimal hydrogen absorption energy than that of FeP and CoP. The carbon shell prevents the oxidation of the phosphides, and the FeCo core provides better conductivity. Our work provides a new method to synthesize multishelled structure catalysts, which has potential applications in the further hydrogen production.
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