During the catalytic process, the microenvironment and surface area of the catalyst will affect the catalytic performance. Hence, an assisted organic linker coated metal-organic framework (MOF) has been applied, to form Ni/HNC (HNC represents hollow nanocage) for electrocatalytic CO₂ reduction. Remarkably, Ni/HNC achieves superb activity with high Faradaic efficiency (FE) of 97.2% at 0.7 V vs. reversible hydrogen electrode (RHE) towards CO₂ conversion to CO. In contrast to Ni/NPC (afforded from the naked MOF), the Ni/HNC displays higher FE and selectivity on CO rather than H₂, owing to the large nanocage which extraordinarily facilitates CO₂ enrichment and the active sites easily accessible. This work provides a general and feasible route to construct high-efficient electrochemical CO₂ reduction reaction (EC-CO₂RR) catalysts via post-modified MOFs.

Selective hydrogenation of the carbonyl bond in α,β-unsaturated carbonyl compounds is rather challenging owing to the more feasible hydrogenation of ethylenic bond from both thermodynamic and kinetic aspects. Here, we demonstrate a facile emulsion-based molecule-nanoparticle self-assembly strategy for the atomic engineering of Ir species on three-dimensional CeO₂ spheres (Ir₁@CeO₂). When applied to the hydrogenation of α,β-unsaturated aldehydes, Ir₁@CeO₂ catalyst remarkably exhibited ~ 100% selectivity towards unsaturated alcohols, whereas the formation of Ir nanoparticles on CeO₂ drastically decreased the selectivity for unsaturated alcohols. Spectroscopic studies revealed that strong metal–support interactions triggered the charge transfer from Ir to CeO₂, leading to the partial reduction of Ce⁴⁺ to Ce³⁺ along with the formation new Ir^δ+–O^2––Ce³⁺(O_V) interfaces. The electrophilic atomic Ir species at the Ir^δ+–O^2––Ce³⁺ (O_V) interfaces would therefore preferentially adsorb and facilitate hydrogenation of polar C=O bond to achieve exceptional selectivity.

In recent years, the isolated single-atom site (ISAS) catalysts have attracted much attention as they are cost-effective, can achieve 100% atom-utilization efficiency, and often display superior catalytic performance. Here, we developed a biomass-assisted pyrolysis-etching-activation (PEA) strategy to construct ISAS metal decorated on N and B co-doped porous carbon (ISAS M/NBPC, M = Co, Fe, or Ni) catalysts. This PEA strategy can be applied in the universal and large-scale preparation of ISAS catalysts. Interestingly, the ISAS M/NBPC (M = Co, Fe, or Ni) catalysts show multi-functional features and excellent catalytic activities. They can be used to conduct different types of catalytic reactions, such as O-silylation (OSI), oxidative dehydrogenation (ODH), and transfer hydrogenation (THG). In addition, we used the transfer hydrogenation of nitrobenzene as a typical reaction and revealed the difference between ISAS Co/NBPC and ISAS Co/NPC (N-doped porous carbon) catalysts by density functional theory (DFT) calculations, and which showed that the decreased barrier of the rate-determining step and the low-lying potential energy diagram indicate that the catalytic activity is higher when ISAS Co/NBPC is used than that when ISAS Co/NPC is used. These results demonstrate that the catalytic performance can be effectively improved by adjusting the coordination environment around the ISAS.

Nickel-iron sulfide has shown attractive activity in electrocatalytic oxygen evolution reaction (OER). However, the effects of low valence sulfur (S²⁻) and metal species on OER in binary nickel-iron sulfide have rarely been systematically studied. Works based on post-catalysis characterization have led to the assumption that the real active species are nickel-iron oxyhydroxide, and that nickel-iron sulfide acts only as a precatalyst. Therefore, to study the role of S, Ni, and Fe for the development of nickel-iron sulfide catalyst is of self-evident importance. Herein, a facile solvothermal method is used to synthesize acetylene black coated with nickel-iron sulfide nanosheets. Electrochemical tests show that the presence of low valence S species makes the catalyst have faster OER kinetics, larger active area, and intermediate active species adsorption area. Therefore, the present study reveals the enhancing effect of low valence sulfur species (S²⁻) on OER in binary nickel-iron sulfide. In situ Raman spectroscopy shows that the generation of γ-NiOOH intermediate is essential and Fe does not directly participate in the oxygen production. Density functional theory (DFT) calculation shows that Ni-OH deprotonation is a rate-determining step for both binary nickel-iron sulfide and nickel sulfide. The addition of Fe into NiS_x lightly increases the charge transfer of Ni atom to O atom, which makes deprotonation easier and thereby improves the OER performance.

The structure and size of bimetallic catalysts play a crucial role in many important chemical transformations. Controlled synthesis of bimetallic nanoparticles avoiding overgrowth and aggregation can be achieved by surfactants, which are always detrimental to catalytic performances and understanding of structure-property relationship. Preparation of surface-clean bimetallic catalysts with uniform size and well-defined structure is still challenging. Herein the Au-Pt bimetallic nanoparticles immobilized on SBA-15 were prepared by facile adsorption-reduction method. Characterizations showed that Au-Pt bimetallic nanoparticles were evenly confined within the mesopores of SBA-15, possessing the uniform size of 6.0 nm and existing in the form of alloy structure. For the first time the Au-Pt bimetallic nanoalloys with Au-to-Pt molar ratio of 5:1 (Au₅Pt₁@SBA-15) exhibited a lot higher activity than monometallic Au@SBA-15 and Pt@SBA-15 catalysts with excellent selectivity towards 1,2,3,4-tetrahydroquinoline for chemoselective hydrogenation of quinoline in water under very mild conditions. It was superior to other heterogeneous catalysts reported to date. The observed properties were related to the synergic effect between Au and Pt. The Pt sites of high electron density originated from the electron transfer between Au and Pt enhanced the ability of H₂ dissociation and then provided a new and main approach to H₂ splitting, while the Au sites accounted for the adsorption and activation of quinoline. This precise synthetic strategy will be very helpful to explore surface-clean gold-based bimetallic catalysts with high performance for selective hydrogenations.

Atomic non-noble metal materials show the potential to substitute noble metals in catalysis. Herein, melamine formaldehyde resin is developed to synthesize atomic iron on mesoporous nitrogen-doped carbon. The triazine units with abundant nitrogen content and cavity can realize effectively anchoring of single metal atoms. The atomic iron with unique charge and coordination characteristics shows superior catalytic performance in dehydrogenation reaction. Various N-heterocycles compounds and amines can be efficiently dehydrogenated into the corresponding products at room temperature, which is the mildest of all reported reaction conditions even when noble metal catalysts are considered. Therefore, development of atomic non-noble metal catalysts with mesoporous structure may provide an effective way to realize the substitution for noble metals in heterogeneous catalysis.