Due to challenges in preparing pure metal clusters and in controlling reactions, the oxides produced by metal clusters reacting with oxygen are often different from traditional ion-molecule products in the gas phase and their reactivity pattern is also largely unveiled yet. In this work, utilizing a customized Re-TOFMS having a home-made cluster source and a flow tube reactor, we have observed the gaseous reactions of Ni_n^± clusters with oxygen and found magic clusters of Ni₁₃O₈^± that dominate the mass distributions. By quantum chemistry calculations, we find that both Ni₁₃O₈^– and Ni₁₃O₈⁺ clusters bear a regular cubic structure with 8 oxygen anchoring the eight angles, however, they have rather different spin accommodations. The Ni₁₃O₈^– clusters have 15 unpaired spin-up electrons exhibiting cubic aromaticity and decent ferromagnetism, while the Ni₁₃O₈⁺ clusters take a lower-spin ground state (11 unpaired electrons), with spin-down population on the central Ni atom pertaining to ferrimagnetism. This is a class of metalloxocube clusters that hold properties of aromaticity and ferromagnetism/ferrimagnetism charcterized by a few spin electrons, which embodies the bonding nature of superatomic compounds and enables to develop cluster-genetic materials of multi-functionality.

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 Fe_n (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.

Hydrogenation of p-nitrophenol (PNP) towards the conversion to p-aminophenol (PAP) by metal catalysis is known as a simple and eco-friendly technique for the production of corresponding industrial and pharmaceutical intermediates. While continuous 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 understood. Utilizing a dry-wet combined strategy, here we have synthesized water-soluble Pd₈ nanoclusters (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 difference (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.

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.