As an alternative for depleting fossil fuel energy, hydrogen economy desires low-cost and efficient hydrogen production from water splitting. In order to explore a cheap, abundant, active, and ...durable catalyst for the electrocatalytic hydrogen evolution reaction (HER), two-dimensional (2D) ceria nanosheets are produced through a thermal decomposition exfoliation method from CeCO3OH with a layer-stacked structure. The additional cobalt dopant promotes formation of oxygen vacancies in ceria nanosheets and, in turn, optimizes hydrogen binding/water dissociation and increases the active sites. As a result, the 2D Co-doped CeO2 nanosheets exhibit an excellent catalytic performance in alkaline HER such that the overpotential is as low as 132 and 215 mV to deliver a high current density of 100 and 500 mA cm–2, respectively, outperforming Pt. Such 2D Co-doped CeO2 nanosheets are also durable HER electrocatalysts, as the activity loss during an extended period of operation is nearly negligible.
Mn−Pt nanocubes were synthesized from platinum acetylacetonate and manganese carbonyl in the presence of oleic acid and oleylamine. The Mn−Pt nanocubes were converted into an ordered MnPt3 ...intermetallic phase upon annealing. The electrocatalytic properties of the Mn−Pt nanocubes and spheres (including oxygen reduction, formic acid oxidation, and methanol oxidation) were tested and found to be shape-dependent. The Mn−Pt nanocubes, which are enclosed by (100) surfaces, showed better activities than their spherical counterparts. These materials are promising new candidates as cathode and anode catalysts in fuel cells.
Display omitted
•Performance of an electrocatalyst is altered through the control of size, composition, morphology and architecture of employed nanomaterials.•Well-defined systems and ...shape-controlled nanocrystals.•Composition-function relationship in electrocatalysis.•Tailoring Electrocatalysis through Surface Modification.•Design and synthesis of high performance electrocatalyst.
Electrocatalysis is a subclass of heterogeneous catalysis that is aimed towards increase of the electrochemical reaction rates that are taking place at the surface of electrodes. Real-world electrocatalysts are usually based on precious metals in the form of nanoparticles due to their high surface-to-volume ratio, which enables better utilization of employed materials. Ability to tailor nanostructure of an electrocatalyst is critical in order to tune their electrocatalytic properties. Over the last decade, that has mainly been achieved through implementation of fundamental studies performed on well-defined extended surfaces with distinct single crystalline and polycrystalline structures. Based on these studies, it has been demonstrated that performance of an electrocatalyst could be significantly changed through the control of size, composition, morphology and architecture of employed nanomaterials. This review outlines the following steps in the process of rational development of an efficient electrocatalyst: 1) electrochemical properties of well-defined surfaces, 2) synthesis and characterization of different classes of electrocatalysts, and 3) correlation between physical properties (size, shape, composition and morphology) and electrochemical behavior (adsorption, electrocatalytic activity and durability) of electrocatalyst. In addition, this is a brief summary of the novel research platforms in the development of functional nanomaterials for energy conversion and storage applications such as fuel cells electrolyzers and batteries.
The electrolysis of water is promising for hydrogen production. The development of high-performance and low-cost hydrogen evolution reaction (HER) electrocatalysts is particularly important for the ...wide application of water electrolyzers. Tuning the hydrogen binding energy (HBE) of materials is an effective way to optimize the HER electrocatalysts, particularly for applications in an acidic environment. Here, we report the discovery of a Pt-free combination, PdMoGaInNi, which has the HBE optimum, via computer-facilitated screening. As the exploratory example of the two-dimensional high-entropy alloy (HEA) for HER, the PdMoGaInNi HEA nanosheets were synthesized to realize the predicted Pt-free combination with optimal HBE. The PdMoGaInNi HEA nanosheets exhibit a high HER activity with low overpotentials of 13 mV at 10 mA cm–2, outperforming commercial Pd/C and Pt/C catalysts. Given the high entropy, lattice distortion, and sluggish diffusion effects of HEA, the PdMoGaInNi shows great long-term durability for at least 200 h in a proton exchange membrane water electrolyzer.
Due to the scarcity and high cost of precious metals, the hydrogen economy would ultimately rely on non-platinum-group-metal (non-PGM) catalysts. The non-PGM-catalyzed oxygen reduction reaction, ...which is the bottleneck for the application of hydrogen fuel cells, is challenging because of the limited activity and durability of non-PGM catalysts. A stabilized single-atom catalyst may be a possible solution to this issue. In this work, we employ a coordination-assisted polymerization assembly strategy to synthesize an atomic Fe and N co-doped ordered mesoporous carbon nanosphere (denoted as meso-Fe–N–C). The meso-Fe–N–C possesses a hierarchical structure with a high surface area of 494.7 m2 g–1 as well as a high dispersion of Fe (2.9 wt %) and abundant N (4.4 wt %). With these beneficial structural properties, the meso-Fe–N–C exhibits excellent activity and durability toward the oxygen reduction reaction, outperforming the state-of-the-art Pt/C electrocatalysts.
The ability to engineer surface properties of nanocrystals (NCs) is important for various applications, as many of the physical and chemical properties of nanoscale materials are strongly affected by ...the surface chemistry. Here, we report a facile ligand-exchange approach, which enables sequential surface functionalization and phase transfer of colloidal NCs while preserving the NC size and shape. Nitrosonium tetrafluoroborate (NOBF4) is used to replace the original organic ligands attached to the NC surface, stabilizing the NCs in various polar, hydrophilic media such as N,N-dimethylformamide for years, with no observed aggregation or precipitation. This approach is applicable to various NCs (metal oxides, metals, semiconductors, and dielectrics) of different sizes and shapes. The hydrophilic NCs obtained can subsequently be further functionalized using a variety of capping molecules, imparting different surface functionalization to NCs depending on the molecules employed. Our work provides a versatile ligand-exchange strategy for NC surface functionalization and represents an important step toward controllably engineering the surface properties of NCs.
In the present study, we used a surface-science approach to establish a functional link between activity and stability of monometallic oxides during the OER in acidic media. We found that the most ...active oxides (Au ≪ Pt < Ir < Ru ≪ Os) are, in fact, the least stable (Au ≫ Pt > Ir > Ru ≫ Os) materials. We suggest that the relationships between stability and activity are controlled by both the nobility of oxides as well as by the density of surface defects. This functionality is governed by the nature of metal cations and the potential transformation of a stable metal cation with a valence state of n = +4 to unstable metal cation with n > +4. A practical consequence of such a close relationship between activity and stability is that the best materials for the OER should balance stability and activity in such a way that the dissolution rate is neither too fast nor too slow.
Electrocatalytic water splitting offers a sustainable route for hydrogen production, enabling the clean and renewable alternative energy system of hydrogen economy. The scarcity and high-cost of ...platinum-group-metal (PGM) materials urge the exploration of high-performance non-PGM electrocatalysts. Herein, a unique hierarchical structure of Ni/V
2
O
3
with extraordinary electrocatalytic performance (e.g., overpotentials as low as 22 mV at 20 mA·cm
−2
and 94 mV at 100 mA·cm
−2
) toward hydrogen evolution reaction in alkaline electrolyte (1 M KOH) is reported. The investigation on the hierarchical Ni/V
2
O
3
with a bimodal size-distribution also offers insight of interfacial engineering that only proper Ni/V
2
O
3
interface can effectively improve H
2
O adsorption, H
2
O dissociation as well as H adsorption, for an efficient hydrogen production.
This work demonstrates the first solution-processable metal–semiconductor nanocomposites with enhanced thermoelectric properties via carrier energy filtering. Platinum nanocrystals are embedded in a ...p-type antimony(III) telluride (Sb2Te3) semiconductor matrix, thus introducing band-bending potentials for holes. By scattering low energy holes, an increase in thermopower is observed. Introduction of Pt nanocrystals also increases carrier concentration thereby partially compensating for reduced electrical conductivity due to the decreased mobility. At room temperature, an improvement in thermoelectric power factor was achieved compared to that of the Sb2Te3 films. This work highlights the possibility of combining a diverse set of n- and p-type semiconductor matrices with nanocrystals to engineer and optimize energy-dependent carrier scattering with the ease of materials processing.
PDF
