Rh Nanosheets Research Articles

Heterointerface engineering of rhombic Rh nanosheets confined on MXene for efficient methanol oxidation

Although metallic rhodium (Rh) is regarded as a promising platinum-alternative anode catalyst of direct methanol fuel cell (DMFC), the conventional “particle-to-face” contact model between Rh and matrix largely limits the overall electrocatalytic performance due to their insufficient cooperative effects. Herein, we report a controllable and robust heterointerface engineering strategy for the bottom-up fabrication of rhombic Rh nanosheets in situ confined on Ti3C2Tx MXene nanolamellas (Rh NS/MXene) via a convenient stereoassembly process. This unique design concept gives the resulting 2D/2D Rh NS/MXene heterostructure intriguing textural features, including large accessible surface areas, strong “face-to-face” interfacial interactions, homogeneous Rh nanosheet distribution, ameliorative electronic structure, and high electronic conductivity. As a consequence, the as-prepared Rh NS/MXene nanoarchitectures exhibit exceptional electrocatalytic methanol oxidation properties in terms of a large electrochemically active surface area of 126.2 m2 g−1Rh, a high mass activity of 1056.9 mA mg−1Rh, and a long service life, which significantly outperform those of conventional particle-shaped Rh catalysts supported by carbon black, carbon nanotubes, reduced graphene oxide, and MXene matrixes as well as the commercial Pt nanoparticle/carbon black and Pd nanoparticle/carbon black catalysts with the same noble metal loading amount. Density functional theory calculations further demonstrate that the direct electronic interaction at the well-contacted 2D/2D heterointerfaces effectively enhances the adsorption energy of Rh nanosheets and induces a left shift of the d-band center, thereby making the Rh NS/MXene configuration suffer less from CO poisoning. This work highlights the importance of rational heterointerface design in the construction of advanced noble metal/MXene electrocatalysts, which may provide new avenues for developing the next-generation DMFC devices.

Ultrathin Rh Nanosheets with Rich Grain Boundaries for Efficient Hydrogen Oxidation Electrocatalysis.

Two-dimensional (2D) Pt-group ultrathin nanosheets (NSs) are promising advanced electrocatalysts for energy-related catalytic reactions. However, improving the electrocatalytic activity of 2D Pt-group NSs through the addition of abundant grain boundaries (GBs) and understanding the underlying formation mechanism remain significant challenges. Herein, we report the controllable synthesis of a series of Rh-based nanocrystals (e.g., Rh nanoparticles, Rh NSs, and Rh NSs with GBs) through a CO-mediated kinetic control synthesis route. In light of the 2D NSs' structural advantages and GB modification, the Rh NSs with rich GBs exhibit an enhanced electrocatalytic activity compared to pure Rh NSs and commercial Pt/C toward the hydrogen oxidation reaction (HOR) in alkaline media. Both experimental results and theoretical computations corroborate that the GBs in the Rh NSs have the capacity to ameliorate the adsorption free energy of reaction intermediates during the HOR, thus resulting in outstanding HOR catalytic performance. Our work offers novel perspectives in the realm of developing sophisticated 2D Pt-group metal electrocatalysts with rich GBs for the energy conversion field.

Self-Interface in Rh Nanosheets-Supported Tetrahedral Rh Nanocrystals for Promoting Electrocatalytic Oxidation of Ethanol.

Direct ethanol fuel cells hold great promise as a power source. However, their commercialization is limited by anode catalysts with insufficient selectivity toward a complete oxidation of ethanol for a high energy density, as well as sluggish catalytic kinetics and low stability. To optimize the catalytic performance, rationally tuning surface structure or interface structure is highly desired. Herein, a facile route is reported to the synthesis of Rh nanosheets-supported tetrahedral Rh nanocrystals (Rh THs/NSs), which possess self-supporting homogeneous interface between Rh tetrahedrons and Rh nanosheets. Due to full leverage of the structural advantages within the given structure and construction of interfaces, the Rh THs/NSs can serve as highly active electro-catalysts with excellent mass activity and selectivity toward ethanol electro-oxidation. The in situ Fourier transform infrared reflection spectroscopy showed the Rh THs/NSs exhibit the highest C1 pathway selectivity of 23.2%, far exceeding that of Rh nanotetrahedra and Rh nanosheets. Density function theory calculations further demonstrated that self-interface between Rh nanosheets and tetrahedra is beneficial for C-C bond cleavage of ethanol. Meanwhile, the self-supporting of 2D nanosheets greatly enhance the stability of tetrahedra, which improves the catalytic stability.

Interstitial carbon atoms enhance both selectivity and activity of rhodium catalysts toward C-C cleavage in direct ethanol fuel cells

Selective breaking of the C-C bond in ethanol holds the key to many industrial processes, including the operation of direct ethanol fuel cells and steam reforming. Interstitial C atoms in the subsurface region of noble-metal catalysts have major impacts on the selectivity and activity, but an understanding of the mechanistic details is still elusive due to their nature of in situ formation and metastability. Herein, we develop a method to obtain stable RhCx (x ≈ 0.5) by introducing C atoms into the interstitial sites of well-defined Rh nanosheets of 8–10 at. layers in thickness, and further elucidate the electronic and geometric effects of the interstitial C atoms on the cleavage of C-C bond. With the introduction of C atoms into half of the octahedral sites, the Rh lattice changes from a cubic to an orthorhombic structure. The lattice expansion induced by the insertion of C atoms, together with the electron transfer between C and Rh atoms, effectively suppresses the coupling reaction between OH* and CH3CO* to form acetic acid while making the cleavage of C-C bond more exothermic. As such, we obtain a selectivity of ethanol to CO2 as high as 18.1 %, much higher than those of the Rh counterpart (10.0 %), together with 3.1-fold improvement in kinetics. Guided by these findings, a new method is also developed to directly introduce C atoms into the subsurface of a commercial Rh black to enhance its selectivity and activity by 2.5- and 1.6- folds, respectively.

Host–Guest Ensemble Effect on Dual-Pt atom-on-Rh Nanosheets Enables High-Efficiency and Anti-CO Alkaline Hydrogen Oxidation

Explicit atomic coordinations of binary metal atoms on low-dimensional host–guest-type bimetallic nanomaterials can arouse unique ensemble effects and significantly improve the catalysis performances, but they confront a formidable challenge in chemical synthesis. Here, we draw on a thermoinduced secondary crystallization process of preprepared amorphous/crystalline hybrid ultrathin Rh nanosheets (NSs) to capture Pt atoms into the two-dimensional (2D) Rh lattice, by which precisely controlled Pt atomic dispersions from a single atom to dual atoms and to clustered atoms can be facilely elected and embedded into the ultrathin Rh hosts. Among them, the dual-Pt atom-on-Rh (denoted as Pt2–Rh) NSs exhibit an extremely high activity and an excellent CO tolerance for the alkaline hydrogen oxidation reaction (HOR), achieving a 18.5 times higher mass activity at 50 mV overpotential than that of commercial Pt/C. Theoretical studies indicate that the host–guest ensemble effect aroused by the specific pairwise Pt2-on-Rh coordination feature can moderately enhance both the surface *H and *OH bindings, which synergistically lower the free energy of the rate-determining Volmer step and thus promote the combination of neighboring *H and *OH to form H2O. Enhanced *H adsorption can also prevent the main available sites from being occupied by hydroxyl groups in alkaline conditions. The free energy diagram and anti-CO experiments coherently indicate that the oxidation of *CO by neighboring *OH to form *COOH is kinetically more favorable to proceed on the Pt2–Rh NSs, effectively preventing the catalysts from being poisoned. This work sheds light on the ensemble effect of host–guest heteroatom coordinations for designing high-efficiency alkaline HOR catalysts.

Facile fabrication of hierarchical ultrathin Rh-based nanosheets for efficient hydrogen evolution.

Rational design of efficient and stable electrocatalysts for the hydrogen evolution reaction (HER) has attracted wide attention. Noble metal-based electrocatalysts with ultrathin structures and highly exposed active surfaces are essential to boost the HER performance, while the simple synthetic strategies remain challenging. Herein, we reported a facile urea-mediated method to synthesize hierarchical ultrathin Rh nanosheets (Rh NSs) without using toxic reducing agents and structure directing agents in the reaction. The hierarchical ultrathin nanosheet structure and grain boundary atoms endow Rh NSs with excellent HER activities, which only requires a lower overpotential of 39 mV in 0.5 M H2SO4 compared to the 80 mV of Rh nanoparticles (Rh NPs). Extending the synthesis method to alloys, hierarchical ultrathin RhNi nanosheets (RhNi NSs) can be also obtained. Benefiting from the optimization of electronic structure and abundant active surfaces, RhNi NSs only require an overpotential of 27 mV. This work provides a simple and promising method to construct ultrathin nanosheet electrocatalysts for highly active electrocatalytic performance.

In-plane strain engineering in ultrathin noble metal nanosheets boosts the intrinsic electrocatalytic hydrogen evolution activity

Strain has been shown to modulate the electronic structure of noble metal nanomaterials and alter their catalytic performances. Since strain is spatially dependent, it is challenging to expose the active strained interfaces by structural engineering with atomic precision. Herein, we report a facile method to manipulate the planar strain in ultrathin noble metal nanosheets by constructing amorphous–crystalline phase boundaries that can expose the active strained interfaces. Geometric-phase analysis and electron diffraction profile demonstrate the in-plane amorphous–crystalline boundaries can induce about 4% surface tensile strain in the nanosheets. The strained Ir nanosheets display substantially enhanced intrinsic activity toward the hydrogen evolution reaction electrocatalysis with a turnover frequency value 4.5-fold higher than the benchmark Pt/C catalyst. Density functional theory calculations verify that the tensile strain optimizes the d-band states and hydrogen adsorption properties of the strained Ir nanosheets to improve catalysis. Furthermore, the in-plane strain engineering method is demonstrated to be a general approach to boost the hydrogen evolution performance of Ru and Rh nanosheets.

CO spillover on ultrathin bimetallic Rh/Rh-M nanosheets

Rh has been regarded as a promising catalyst for ethanol-oxidation reaction (EOR). Nevertheless, Rh is vulnerable to CO poisoning. In this work, we demonstrate a facile strategy for constructing a unique class of ultrathin Rh/Rh-M nanosheets, on which CO can diffuse from the Rh site to the M site. Detailed experiments, characterizations, and theoretical simulations have been conducted to validate the CO spillover effects on Rh/Rh-M nanosheets (NSs). Moreover, the significance of the CO spillover effect has been demonstrated by catalyzing the EOR, where Rh/Rh-M NSs with CO spillover display much higher activity, higher CO 2 selectivity, and stronger resistance to CO poisoning compared with pure Rh NSs. Consequently, the Faraday efficiencies (FEs) of CO 2 of the optimal catalyst (e.g., Rh 79 Co 21 NSs) are 70.3% and 75.5% at 0.7 and 0.8 V RHE , respectively, and these are much higher than those of Rh NSs (62.0% and 64.3% at 0.7 and 0.8 V RHE , respectively). • A versatile strategy for the fabrication of Rh/Rh-M nanosheets • CO can spill from Rh-site to M-site Rh/Rh-M nanosheets • CO spillover effect enhances the stability of Rh to CO poisoning • Rh-Co nanosheets display promising performance for ethanol oxidation Noble metals generally suffer from deactivation due to their strong adsorption abilities to some poisoning intermediates, such as CO. Despite great efforts that have been devoted to the modification of noble-metal catalysts to regulate their surface properties to prevent them from being poisoned, it is challenging to balance the activity, selectivity, and stability of noble-metal catalysts. In this work, we have successfully fabricated a unique class of ultrathin Rh/Rh-M (M = Co, Mn, Fe, and Ni) nanosheets with a strong CO spillover effect for enhanced catalysis. Benefitting from the specific structures of Rh/Rh-M nanosheets (NSs), CO can spill from Rh sites of ultrathin Rh nanosheets to M sites of RhM nanoparticles, which leads to the weakened CO adsorption on Rh sites and strengthened CO adsorption on M sites. This work provides a facile strategy for strengthening the resistance to CO poisoning through the CO spillover effects, which may attract great interests of researchers in diverse fields. A facile strategy for fabricating the ultrathin Rh/Rh-M (M = Co, Mn, Fe, and Ni) nanosheets were proposed. Owing to the unique structures, CO can spillover from the Rh site to the M site on ultrathin Rh/Rh-M nanosheets, leading to significantly strengthened resistance to CO poisoning and enhanced ethanol-oxidation reaction performance.

Electrodeposition of a Three-Dimensional Nanostructure Composed of 2D Maple Leaf-like Rh Nanosheets for Formic Acid Oxidation

Two-dimensional (2D) noble metal nanostructures have abundant active sites and are ideal catalysts for fuel cell reactions. However, it is still a huge challenge to realize the synthesis of precious metal nanosheets (NSs) with a clean surface. Here, we employed a square-wave potential electrodeposition method to synthesize a three-dimensional (3D) nanostructure composed of 2D maple leaf-like Rh NSs without introducing any surfactants and capping agents. The factors affecting the electrochemical growth of Rh nanoparticles (NPs) were carefully checked. Studies found that the balance between the growth and etching played the key role in the formation of a 3D nanostructure composed of 2D maple leaf-like Rh NSs. Due to the unique morphology and clean surface with a (111) facet, they exhibited excellent electrocatalytic activity and stability to the formic acid oxidation reaction. The peak current density of the maple leaf-like Rh NSs was 3.66 mA cm–2, which was much higher than those of other Rh NPs prepared by electrodeposition. This work could provide a new idea to construct 3D nanocatalysts with a clean surface for fuel cells.

Ultrathin Amorphous/Crystalline Heterophase Rh and Rh Alloy Nanosheets as Tandem Catalysts for Direct Indole Synthesis.

Heterogeneous noble-metal-based catalysis plays an essential role in the production of fine chemicals. Rh-based catalysts are one of the most active candidates for indole synthesis. However, it is still highly desired to develop heterogeneous Rh-based catalysts with high activity and selectivity. In this work, a general, facile wet-chemical method is reported to synthesize ultrathin amorphous/crystalline heterophase Rh and Rh-based bimetallic alloy nanosheets (NSs), including RhCu, RhZn, and RhRu. Impressively, the amorphous/crystalline heterophase Rh NSs exhibit enhanced catalytic activity toward the direct synthesis of indole compared to the crystalline counterpart. Importantly, the obtained amorphous/crystalline heterophase RhCu alloy NSs can further enhance the selectivity to indole of >99.9% and the conversion is 100%. This work demonstrates the importance of phase engineering and metal alloying in the rational design and synthesis of tandem heterogeneous catalysts toward fine chemical synthesis.

Selective Ethanol Oxidation Reaction at the Rh-SnO2 Interface.

Direct ethanol fuel cells (DEFCs) are regarded as an attractive power source with high energy density, bio-renewability, and convenient storage and transportation. However, the anodic reaction of DEFCs, that is, the ethanol oxidation reaction (EOR), suffers from poor efficiency due to the low selectivity to CO2 (C1 pathway) and high selectivity to CH3 COOH (C2 pathway). In this study, the selective EOR to CO2 can be achieved at the Rh-SnO2 interface in SnO2 -Rh nanosheets (NSs). The optimized catalyst of 0.2SnO2 -Rh NSs/C exhibits excellent alkaline EOR performance with a mass activity of 213.2 mA mgRh -1 and a Faraday efficiency of 72.8% for the C1 pathway, which are 1.7 and 1.9 times higher than those of Rh NSs/C. Mechanism studies indicate that the strong synergy at the Rh-SnO2 interface significantly promotes the breaking of CC bond of C2 H5 OH to form CO2 , and facilitates oxidation of the poisonous intermediates (* CO and * CH3 ) to suppress the deactivation of the catalyst. This work not only provides a highly selective, active, and stable catalyst for the EOR, but also promotes fundamental research for the design of efficient catalysts via interface modification.

Hierarchical porous Rh nanosheets for methanol oxidation reaction

Hierarchical porous precious metal-based nanosheets with ultrathin structures and highly exposed active surfaces are desirable in energy conversion technology, while robust synthetic strategies remain challenging. Here, we report a facile 1-hydroxyethylidene-1,1-diphosphonic acid (HEDP)-mediated approach to synthesize hierarchical porous Rh nanosheets (HP-Rh NSs), following the formation mechanism of emulsion-induced soft template. When HP-Rh NSs are applied to the methanol oxidation reaction (MOR), abundant edge/grain-boundary atoms and the ultrathin porous structure endow HP-Rh NSs with a mass activity of 333 A g−1 at 0.63 V, which are 5.8-fold enhancements compared with traditional commercial Pt black (57.4 A g−1). Meanwhile, the peak potential of MOR on HP-Rh NSs is 0.2 V lower than that on commercial Pt black. With the aid of theoretical calculations, larger methanol adsorption energy and the lower energy barrier reaction path are responsible for superior MOR activity on Rh HP-Rh NSs than commercial Pt black.

Facile Strategy To Prepare Rh Nanosheet-Supported PtRh Nanoparticles with Synergistically Enhanced Catalysis in Oxidation

Here, we report the one-pot synthesis of metal-based zero-dimensional (0D)/two-dimensional (2D) nanocomposites via a modified seed-mediated growth method. In this strategy, two metal precursors (H2PtCl6·6H2O and Rh(acac)3) were mixed together with HCHO as a reductant, followed by a solvothermal treatment, producing homogeneous PtRh bimetallic nanoparticles (NPs) supported on ultrathin Rh nanosheets (NSs) with trapezoidal shape and crystalline/amorphous hetero-phase characteristics. Intriguingly, successive processes including generation of PtRh NPs, formation of Rh NSs, and immobilization of PtRh NPs on Rh NSs were involved in the synthesis, creating a novel 0D/2D PtRh/Rh nanostructure. Several experimental parameters (reductant, precursor, surfactant, solvent, and temperature) were crucial to the formation of a unique structure, during which the preferentially formed Pt atoms/clusters as seeds not only accelerated the reduction of Rh precursors to form PtRh NPs but directed the formation of Rh NSs around PtRh NPs. Owing to both structural and electronic effects, PtRh/Rh exhibited synergistically enhanced activity in the aerobic oxidation. Mechanistic study further revealed that the reaction obeyed the Michaelis–Menten theory and PtRh/Rh-catalysis originated from both generation of important reactive oxygen species and rapid electron transfer. The results provide a facile yet effective avenue to fabricate a new type of Pt-based heterogeneous catalysts.

Ultrathin Rh nanosheets as a highly efficient bifunctional electrocatalyst for isopropanol-assisted overall water splitting

In this work, we synthesized ultrathin Rh nanosheets (Rh-NSs) with atomic thickness, which revealed excellent activity for the hydrogen evolution reaction (HER) and super activity and extraordinary selectivity for the isopropanol oxidation reaction (IOR) in alkaline medium. When using Rh-NSs as a bifunctional electrocatalyst for water electrolysis in the presence of isopropanol, a voltage of only 0.4 V was required for H2 production, accompanied by the production of valuable acetone at the anode.

Single-layer Rh nanosheets with ultrahigh peroxidase-like activity for colorimetric biosensing

When the dimensionality of layered compounds decreases to the physical limit, ultimate two-dimensional (2D) anisotropy and/or quantum confinement effects may lead to extraordinary physicochemical attributes. Here, we report single-layer Rh nanosheets (NSs) exhibiting ultrahigh peroxidase-like activity, far exceeding that of horseradish peroxidase (HRP) and of most known layered nanomaterial-based peroxidase mimics. Considering per NS as an active subunit, the Rh NSs displayed a catalytic rate constant (Kcat) as high as 4.45 × 105 s–1 to H2O2, two orders of magnitude higher than those of HRP and Rh nanoparticles. The high atom efficiency of the Rh NSs can be attributed to the full exposure of surface-active Rh atoms, which greatly facilitates electron transfer and formation of superoxide anions, representing reactive oxygen species in the catalytic process. As a proof-of-concept application, the Rh NSs were successfully used as peroxidase mimics for the colorimetric detection of H2O2 and xanthine, with high sensitivity and selectivity. Moreover, a simple, rapid, and sensitive Rh-based paper sensor for ascorbic acid was also developed. In summary, this work provides a novel example of single-layer metallic NSs for biosensing.

Rhodium Nanosheets–Reduced Graphene Oxide Hybrids: A Highly Active Platinum-Alternative Electrocatalyst for the Methanol Oxidation Reaction in Alkaline Media

For the large-scale commercialization of direct methanol fuel cells, developing Pt-alternative anode electrocatalysts with low cost and high activity plays an important role. In this work, a one-pot hydrothermal method has been developed for the direct synthesis of the Rh nanosheets (Rh-NSs) on reduced graphene oxide (RGO). The newly prepared Rh-NSs/RGO hybrids have great electrocatalytic activity for the methanol oxidation reaction (MOR) in alkaline media, much better than single-component Rh nanoparticles (Rh-NPs) and Rh nanoparticles/RGO (Rh-NPs/RGO) hybrids, originating from the two-dimensional structure of Rh nanosheets and excellent physical/chemical property of the RGO. Very importantly, cyclic voltammetry (CV) measurements show the onset oxidation potential of the MOR at the Rh-NSs/RGO hybrids negatively shift ca. 120 mV compared to the commercial Pt/C electrocatalyst. Meanwhile, CV measurements show that the MOR current at the Rh-NSs/RGO hybrids is 3.6 times bigger than that at the commercial Pt/...

Integration of Quantum Confinement and Alloy Effect to Modulate Electronic Properties of RhW Nanocrystals for Improved Catalytic Performance toward CO2 Hydrogenation.

The d-band center and surface negative charge density generally determine the adsorption and activation of CO2, thus serving as important descriptors of the catalytic activity toward CO2 hydrogenation. Herein, we engineered the d-band center and negative charge density of Rh-based catalysts by tuning their dimensions and introducing non-noble metals to form an alloy. During the hydrogenation of CO2 into methanol, the catalytic activity of Rh75W25 nanosheets was 5.9, 4.0, and 1.7 times as high as that of Rh nanoparticles, Rh nanosheets, and Rh73W27 nanoparticles, respectively. Mechanistic studies reveal that the remarkable activity of Rh75W25 nanosheets is owing to the integration of quantum confinement and alloy effect. Specifically, the quantum confinement in one dimension shifts up the d-band center of Rh75W25 nanosheets, strengthening the adsorption of CO2. Moreover, the alloy effect not only promotes the activation of CO2 to form CO2δ- but also enhances the adsorption of intermediates to facilitate further hydrogenation of the intermediates into methanol.

A facile surfactant-free synthesis of Rh flower-like nanostructures constructed from ultrathin nanosheets and their enhanced catalytic properties

Rh is an important catalyst that is widely used in a variety of organic reactions. In recent years, many efforts have focused on improving its catalytic efficiency by fabricating catalyst nanoparticles with controlled size and morphology. However, the frequently employed synthesis route using organic compounds either as the reaction medium or capping agent often results in residual molecules on the catalyst surface, which in turn drastically diminishes the catalytic performance. Herein, we report a facile, aqueous, surfactant-free synthesis of a novel Rh flowerlike structure obtained via hydrothermal reduction of Rh(acac)3 by formaldehyde. The unique Rh nanoflowers were constructed from ultrathin nanosheets, whose basal surfaces comprised {111} facets with an average thickness of ~1.1 nm. The specific surface area measured by CO stripping was 79.3 m2·g−1, which was much larger than that of commercial Rh black. More importantly, the Rh nanoflower catalyst exhibited excellent catalytic performance in the catalytic hydrogenation of phenol and cyclohexene, in contrast to the commercial Rh black and polyvinyl pyrrolidone (PVP)-capped Rh nanosheets exposed by similar {111} basal surfaces.

Free-standing iridium and rhodium-based hierarchically-coiled ultrathin nanosheets for highly selective reduction of nitrobenzene to azoxybenzene under ambient conditions.

The fabrication of atom-layered two dimensional (2D) noble metal nanosheets (NSs) in a face-centered cubic (fcc) structure is of broad scientific and technological importance, yet this remains a challenge due to the intrinsic cubic symmetry and high surface energy of fcc noble metals. Herein, we report a solid-liquid interface mediated 2D growth method towards the synthesis of hierarchically-coiled ultrathin Ir NSs (thickness <2 nm) and Rh NSs (0.8 nm thick), and bimetallic Ir-Rh NSs (1.2 nm thick) and Pt-Rh NSs (1.2 nm thick) using the benzyl alcohol solvothermal approach. The formation of NSs was attributed to the 2D oriented attachment of tiny seeds through the lateral growth stemming from the abundant defect sites of the seeds produced in the heterogeneous system. The free-standing Ir NSs, Rh NSs and Ir-Rh NSs exhibited high selectivities (from 83.9% to 88.5%) towards the selective reduction of nitrobenzene to azoxybenzene in ethanol at room temperature with 1 atm of hydrogen, because the condensation step of nitrosobenzene (PhNO) and phenylhydroxylamine (PhNHOH) was more exothermic than the dissociation step of Ph-NHOH on the (111) facets of the NSs under alkaline conditions, as indicated by density functional theory (DFT) calculations.

Single-Crystalline Rhodium Nanosheets with Atomic Thickness.

CO confinement strategy for ultrathin Rh nanosheets: CO is introduced as a confining agent to regulate the anisotropic growth of unique 2D structure. The single-crystalline Rh nanosheets have a thickness of three to five atomic layers and tunable edge length ranging from 500 to 1300 nm. By understanding the formation mechanism, surface-clean Rh nanosheets are also prepared and display better catalytic performance that their surfactant-capped nanosheets.