Water electrolysis offers a promising energy conversion and storage technology for mitigating the global energy and environmental crisis, but there still lack highly efficient and pH-universal ...electrocatalysts to boost the sluggish kinetics for both cathodic hydrogen evolution reaction (HER) and anodic oxygen evolution reaction (OER). Herein, we report uniformly dispersed iridium nanoclusters embedded on nitrogen and sulfur co-doped graphene as an efficient and robust electrocatalyst for both HER and OER at all pH conditions, reaching a current density of 10 mA cm
with only 300, 190 and 220 mV overpotential for overall water splitting in neutral, acidic and alkaline electrolyte, respectively. Based on probing experiments, operando X-ray absorption spectroscopy and theoretical calculations, we attribute the high catalytic activities to the optimum bindings to hydrogen (for HER) and oxygenated intermediate species (for OER) derived from the tunable and favorable electronic state of the iridium sites coordinated with both nitrogen and sulfur.
Supported noble metal nanoparticles (including nanoclusters) are widely used in many industrial catalytic processes. While the finely dispersed nanostructures are highly active, they are usually ...thermodynamically unstable and tend to aggregate or sinter at elevated temperatures. This scenario is particularly true for supported nanogold catalysts because the gold nanostructures are easily sintered at high temperatures, under reaction conditions, or even during storage at ambient temperature. Here, we demonstrate that isolated Au single atoms dispersed on iron oxide nanocrystallites (Au
1
/FeO
x
) are much more sinteringresistant than Au nanostructures, and exhibit extremely high reaction stability for CO oxidation in a wide temperature range. Theoretical studies revealed that the positively charged and surface-anchored Au1 atoms with high valent states formed significant covalent metal-support interactions (CMSIs), thus providing the ultra-stability and remarkable catalytic performance. This work may provide insights and a new avenue for fabricating supported Au catalysts with ultra-high stability.
Abstract
The ability to precisely engineer the doping of sub-nanometer bimetallic clusters offers exciting opportunities for tailoring their catalytic performance with atomic accuracy. However, the ...fabrication of singly dispersed bimetallic cluster catalysts with atomic-level control of dopants has been a long-standing challenge. Herein, we report a strategy for the controllable synthesis of a precisely doped single cluster catalyst consisting of partially ligand-enveloped Au
4
Pt
2
clusters supported on defective graphene. This creates a bimetal single cluster catalyst (Au
4
Pt
2
/G) with exceptional activity for electrochemical nitrogen (N
2
) reduction. Our mechanistic study reveals that each N
2
molecule is activated in the confined region between cluster and graphene. The heteroatom dopant plays an indispensable role in the activation of N
2
via an enhanced back donation of electrons to the N
2
LUMO. Moreover, besides the heteroatom Pt, the catalytic performance of single cluster catalyst can be further tuned by using Pd in place of Pt as the dopant.
Ligand‐induced surface restructuring with heteroatomic doping is used to precisely modify the surface of a prototypical Au25(SR1)18− cluster (1) while maintaining its icosahedral Au13 core for the ...synthesis of a new bimetallic Au19Cd3(SR2)18− cluster (2). Single‐crystal X‐ray diffraction studies reveal that six bidentate Au2(SR1)3 motifs (L2) attached to the Au13 core of 1 were replaced by three quadridentate Au2Cd(SR2)6 motifs (L4) to create a bimetallic cluster 2. Experimental and theoretical results demonstrate a stronger electronic interaction between the surface motifs (Au2Cd(SR2)6) and the Au13 core, attributed to a more compact cluster structure and a larger energy gap of 2 compared to that of 1. These factors dramatically enhance the photoluminescence quantum efficiency and lifetime of crystal of the cluster 2. This work provides a new route for the design of a wide range of bimetallic/alloy metal nanoclusters with superior optoelectronic properties and functionality.
On the surface of it: Ligand‐induced surface restructuring with heteroatomic doping is used to precisely modify the surface of a prototypical Au25(SR1)18− cluster while maintaining its icosahedral Au13 core for the synthesis of a new bimetallic Au19Cd3(SR2)18− cluster.
Abstract
Single-atom catalysts (SACs) have been applied in many fields due to their superior catalytic performance. Because of the unique properties of the single-atom-site, using the single atoms as ...catalysts to synthesize SACs is promising. In this work, we have successfully achieved Co
1
SAC using Pt
1
atoms as catalysts. More importantly, this synthesis strategy can be extended to achieve Fe and Ni SACs as well. X-ray absorption spectroscopy (XAS) results demonstrate that the achieved Fe, Co, and Ni SACs are in a M
1
-pyrrolic N
4
(M= Fe, Co, and Ni) structure. Density functional theory (DFT) studies show that the Co(Cp)
2
dissociation is enhanced by Pt
1
atoms, thus leading to the formation of Co
1
atoms instead of nanoparticles. These SACs are also evaluated under hydrogen evolution reaction (HER) and oxygen evolution reaction (OER), and the nature of active sites under HER are unveiled by the
operando
XAS studies. These new findings extend the application fields of SACs to catalytic fabrication methodology, which is promising for the rational design of advanced SACs.
Doping Cd atom(s) into gold clusters is very promising in both theoretical study and practical applications. However, it has long been a challenge to synthesize heavily Cd‐doped AuCd bimetallic ...clusters and thereby reveal their structure‐property correlations. Herein a novel AuCd bimetallic cluster: Au16Cd16(SC6H11)20 (SC6H11 denotes deprotonated cyclohexanethiol) with a Cd to Au atomic ratio of 1:1 is reported. The precise structure of the cluster determined by single crystal X‐ray diffraction demonstrates that it has a unique hexatetrahedron Au14 core and a distinctive shell. Intriguingly, due to the special protecting motifs, the cluster exhibits high stability in various conditions studied, indicating that the geometric structure is crucial in determining the stability of the cluster. Most importantly, the photothermal property of the cluster has been investigated in comparison with those of M13‐kernel (M denotes metal atoms) clusters, and the results imply that the compactness and the Cd atom doping of the core play important roles in dictating the photothermal effect of the cluster. The authors believe that this work will provide some ideas for the rational design of clusters with high stability and excellent photothermal property.
A novel AuCd cluster with the highest Cd‐Au ratio, Au16Cd16(SC6H11)20, is reported. It has a unique Au14 core and a distinctive shell comprised of Au‐Cd‐S synergistic protection motifs. The shell structure dictates the stability of the cluster, and most importantly, the core structure plays an essential role in tuning the photothermal properties of clusters.
High-efficiency water electrolysis is the key to sustainable energy. Here we report a highly active and durable RuIrO
(x ≥ 0) nano-netcage catalyst formed during electrochemical testing by in-situ ...etching to remove amphoteric ZnO from RuIrZnO
hollow nanobox. The dispersing-etching-holing strategy endowed the porous nano-netcage with a high exposure of active sites as well as a three-dimensional accessibility for substrate molecules, thereby drastically boosting the electrochemical surface area (ECSA). The nano-netcage catalyst achieved not only ultralow overpotentials at 10 mA cm
for hydrogen evolution reaction (HER; 12 mV, pH = 0; 13 mV, pH = 14), but also high-performance overall water electrolysis over a broad pH range (0 ~ 14), with a potential of mere 1.45 V (pH = 0) or 1.47 V (pH = 14) at 10 mA cm
. With this universal applicability of our electrocatalyst, a variety of readily available electrolytes (even including waste water and sea water) could potentially be directly used for hydrogen production.
Oxygen electrochemistry plays a critical role in clean energy technologies such as fuel cells and electrolyzers, but the oxygen evolution reaction (OER) severely restricts the efficiency of these ...devices due to its slow kinetics. Here, we show that via incorporation of lithium ion into iridium oxide, the thus obtained amorphous iridium oxide (Li–IrO x ) demonstrates outstanding water oxidation activity with an OER current density of 10 mA/cm2 at 270 mV overpotential for 10 h of continuous operation in acidic electrolyte. DFT calculations show that lithium incorporation into iridium oxide is able to lower the activation barrier for OER. X-ray absorption characterizations indicate that both amorphous Li–IrO x and rutile IrO2 own similar IrO6 octahedron units but have different IrO6 octahedron connection modes. Oxidation of iridium to higher oxidation states along with shrinkage in the Ir–O bond was observed by in situ X-ray absorption spectroscopy on amorphous Li–IrO x , but not on rutile IrO2 under OER operando conditions. The much more “flexible” disordered IrO6 octahedrons with higher oxidation states in amorphous Li–IrO x as compared to the periodically interconnected “rigid” IrO6 octahedrons in crystalline IrO2 are able to act as more electrophilic centers and thus effectively promote the fast turnover of water oxidation.
Abstract
Amides are one of the most important organic compounds that are widely applied in medicine, biochemistry, and materials science. To find an efficient synthetic method of amides is a ...challenge for organic chemistry. We report here a facile synthesis method of primary and secondary amides through a direct amidation of esters with sodium amidoboranes (NaNHRBH
3
, R = H, Me), at room temperature without using catalysts and other reagents. This process is rapid and chemoselective, and features quantitative conversion and wide applicability for esters tolerating different functional groups. The experimental and theoretical studies reveal a reaction mechanism with nucleophilic addition followed by a swift proton transfer-induced elimination reaction.
Two salts (2 and 4) containing the radical cations of complexed diphosphenes have been isolated and characterized by electron paramagnetic resonance (EPR) spectroscopy, IR spectroscopy, and ...single‐crystal X‐ray diffraction. The P−P bond is coordinated to the Cr center either in an end‐on (in 2) or a side‐on (in 4) fashion. The spin density of the radical is delocalized over the Cr atom and the two P atoms in 2 whereas the unpaired electron is mainly localized on the Cr atom in 4. This work provides the first example of a complexed diphosphene radical (2) featuring novel three‐center three‐electron (3c‐3e) π‐bonding in the Cr‐P‐P unit, and the first example of a 17 e Cr radical with a side‐on π‐bonded ligand (4).
The radical cation of a complexed diphosphene has been isolated and characterized. The electron spin density of the radical is delocalized over the Cr and the two P atoms. The Cr‐P‐P linkage of the complexed diphosphene radical features three‐center three‐electron (3c‐3e) π‐bonding.
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