Plasma-Assisted Dinitrogen Activation via Dual Platinum Cluster Catalysis:A Strategy for Ammonia Synthesis under Mild Conditions

The activation and reduction of N_(2)to produce ammonia under mild conditions is of great interest,but challenges remain.Here,we report a breakthrough in efficient dinitrogen cleavage by employing small Ptn+(n=1–4)clusters and convenient plasma assistance.The reactivity of Pt3+is found to be substantially higher than that of other clusters,and the formed Pt3N7+shows prominent mass abundance among the odd-nitrogen products.We illustrate that a chain reaction path within dual cluster cooperation,especially via a“3+2”mode,is beneficial to N≡N triple bond dissociation,embodying efficient synergistic catalysis.A key intermediate containing a bridged N_(2)of binding with two Pt clusters facilitates N_(2)activation with significantly enhanced interactions between the d orbitals of Pt and the antibondingπ*-orbitals of N_(2).Furthermore,by reacting the Pt_(n)N_(m)+clusters with H_(2),we observed hydrogenation products of both evenand odd-hydrogen species,indicative of ammonia release.The in situ synthesized platinum nitride clusters,typically Pt_(3)N_(7)+,induce a highly active N site for hydrogen anchoring,enabling a cost-effective hydrotreating process for ammonia synthesis.

Nitrogen reduction reaction on small iron clusters supported by N-doped graphene:A theoretical study of the atomically precise active-site mechanism

Nonprecious metal catalysts are known of significance for electrochemical N2 reduction reaction(NRR)of which the mechanism has been illustrated by ongoing investigations of single atom catalysis.However,it remains challenging to fully understand the size-dependent synergistic effect of active sites inherited in substantial nanocatalysts.In this work,four types of small iron clusters Fen(n=1–4)supported on nitrogen-doped graphene sheets are constructed to figure out the size dependence and synergistic effect of active sites for NRR catalytic activities.It is revealed that Fe3 and Fe4 clusters on N4G supports exhibit higher NRR activity than single-iron atom and iron dimer clusters,showing lowered limiting potential and restricted hydrogen evolution reaction(HER)which is a competitive reaction channel.In particular,the Fe4-N4G displays outstanding NRR performance for“side-on”adsorption of N2 with a small limiting potential(−0.45 V).Besides the specific structure and strong interface interaction within the Fe4-N4G itself,the high NRR activity is associated with the unique bonding/antibonding orbital interactions of N-N and N-Fe for the adsorptive N2 and NNH intermediates,as well as relatively large charge transfer between N2 and the cluster Fe4-N4G.

Nitrogen-carbon layer coated nickel nanoparticles for efficient electrocatalytic reduction of carbon dioxide

The application of nickel in electrocatalytic reduction of CO2 has been largely restricted by side reaction (hydrogen evolution reaction) and catalyst poisoning.Here we report a new strategy to improve the electrocatalytic performance of nickel for CO2 reduction by employing a nitrogen-carbon layer for nickel nanoparticles.Such a nickel electrocatalyst exhibits high Faradaic efficiency 97.5% at relatively low potential of-0.61 V for the conversion of CO2 to CO.Density functional theory calculation reveals that it is thermodynamically accomplishable for the reduction product CO to be removed from the catalyst surface,thus avoiding catalyst poisoning.Also,the catalyst renders hydrogen evolution reaction to be suppressed and hence reasonably improves catalytic performance.

In-situ generation and global property profiling of metal nanoclusters by ultraviolet laser dissociation-mass spectrometry

Metal nanoclusters are promising nanomaterials with unique properties, but only a few ones with specific numbers of metal atoms can be obtained and studied up to now. In this study, we establish a new paradigm of in-situ generation and global study of metal nanoclusters with different sizes, constitutions, and charge states, including both accurate constitution characterization and global activity profiling. The complex mixtures of metal nanoclusters are produced by employing single-pulsed 193-nm laser dissociation of monolayer-protected cluster(MPC) precursors within a high-resolution mass spectrometry(HRMS). More than400 types of bare gold nanoclusters including novel multiply charged(2+ and 3+), S-/P-doped, and silver alloy ones can be efficiently generated and accurately characterized. A distinct size(1 to 142 atoms)-and charge(1+ to 3+)-hierarchy reactivity is clearly observed for the first time. This global cluster study might greatly promote the developments and applications of novel metal nanoclusters.

A facile method to synthesize water-soluble Pd8 nanoclusters unraveling the catalytic mechanism of p-nitrophenol to p-aminophenol

Hydroge nation of p-n itrophe nol(PNP)towards the con versi on to p-ami nophe no I(PAP)by metal catalysis is known as a simple and I eco-frie ndly tech nique for the production of corresp on ding in dustrial and pharmaceutical in termediates.While continu ous efforts are paid for§more sustainable and greener procedures by using transition metal catalysts,atomic-precise reaction mechanism for the PNP-to-PAP is still illusive to be fully un derstood.Utilizi ng a dry-wet com bined strategy,here we have syn thesized water-soluble Pd8 nano clusters(NCs)with mercaptosuccinic acid(H2SMA)as the ligand,and the Pd8 NCs found high catalytic performance for the conversion of PNP-to-PAP,as identified by the electrospray ionization mass spectrometer(ESI-MS)measurement.The gradual changes over time of ultraviolet-visible(UV-vis)spectra of PNP really display the catalytic reduction by NaBH4 in presence of Pd8 NCs.Further,in-depth charge transfer interactions between PNP and the Pd8 clusters at the proton-rich conditions are investigated by natural bond orbital(NBO)analysis and electron density differenee(EDD)analysis.The exothermic and kinetic-favorable reaction pathways are addressed,based on successive PNP hydrogenation and H2O removal processes,clarifying the reaction mechanism of Pd catalysts.It is worth noting that this solid-state synthetic route for such Pd8 clusters enables gram-scale quantity of production in likely practical use.

Small gold clusters catalyzing oxidant-free dehydrogenation of glycerol initiated by methene hydrogen atom transfer

Developing oxygen-free methodology for the conversion of alcohols to carbonyls is essentially important because it suppresses the over-oxidation of alcohols to carboxylic acids and enables the production of energetic hydrogen.Here we report a finding of feasible oxidant-free dehydrogenation of glycerol over chemically-pure Au clusters synthesized by a green chemistry method named as laser ablation in liquid(LAL).As results,glycerol is dehydrogenated to form glyceraldehyde which undergoes subsequent dehydrogenation to hydroxymethyl glyoxal.For this,reaction dynamics calculations find interesting dehydrogenation reaction pathways with a low-energy barrier of transition state initiated by hydrogen atom transfer from methene,which differs from the general reaction mechanism based on hydroxyl.Furthermore,it is interesting that the presence of additionalààOH group molecules especially H2O can effectively lower the energy barrier in the activation of the OààH and CààH bonds in glycerol.This principle is also applicable to the oxidant-free dehydrogenation of methanol and ethanol,helping to fully understand the catalytic mechanism of alcohols conversion chemistry.

A DFT study of CO_2 electrochemical reduction on Pb(211) and Sn(112)

Electrochemical reduction of CO2 has the benefit of turning greenhouse gas emissions into useful resources. We performed a comparative study of the electrochemical reduction of CO2 on stepped Pb(211) and Sn(112) surfaces based on the results of density functional theory slab calculations. We mapped out the potential energy profiles for electrochemical reduction of CO2 to formate and other possible products on both surfaces. Our results show that the first step is the formation of the adsorbed formate(HCOO*) species through an Eley-Rideal mechanism. The formate species can be reduced to HCOO- through a oneelectron reduction in basic solution, which produces formic acid as the predominant product. The respective potentials of forming HCOO* are predicted to be -0.72 and -0.58 V on Pb and Sn. Higher overpotentials make other reaction pathways accessible, leading to different products. On Sn(112), CO and CH4 can be generated at -0.65 V following formate formation. In contrast, the limiting potential to access alternative reaction channels on Pb(211) is -1.33 V, significantly higher than that of Sn.

Co^(-)_(12)C_(12)——metallo-carbospherenes:一类新型的具有储氢潜能的幻数团簇

早期研究发现前过渡金属(TM)可形成一类超稳定的M_(8)C_(12)金属碳化物Met-Cars;然而,尚不清楚后过渡金属是否也能形成类似的特殊物种.本文通过研究阴离子团簇Co_(n)-(n=7~33)与乙炔的反应,发现了Co_(12)C_(12)团簇异常的化学惰性,其突出的质谱丰度与其他纯金属簇及其碳化物形成鲜明对比.全局最低能量结构搜索和光电子能谱实验查证了该团簇具有高对称性的球状空心笼结构,且包含规则交替的C_(1)和C_(2)单元.相关实验和理论研究揭示了Ni~-团簇与乙炔的反应也生成稳定的Ni_(12)C_(12),且具有类似的笼状结构.进一步研究深入阐述了这一类新型“金属碳球烯”的稳定性机制和特殊极性键RC-CR的化学本质,并揭示了亚纳米Co_(12)C_(12)笼状团簇的储氢潜能.

Enhanced Catalysis of Pt_(3) Clusters Supported on Graphene for N–H Bond Dissociation

We report an in-depth study of catalytic N–H bond dissociation with typical platinum clusters on gra-phene supports.Among all the pristine graphene-and defective graphene-supported Pt clusters of different sizes that were studied,the Pt_(3)/G cluster possesses the highest reactivity and lowest activa-tion barriers for each step of N–H dissociation in the decomposition of ammonia.