To address the sluggish kinetics of the oxygen evolution reaction (OER), a potential approach is to rationally design and fabricate extremely effective single atom catalysts (SACs). Using an appropriate matrix to stabilize single-atom active centers with optimal geometric and electronic structures is crucial for enhancing catalytic activity. Herein, we report the design and fabrication of Ir single atoms on NiFeZn layered double hydroxide (Ir-SAC/NiFeZn-LDH) electrocatalyst for highly efficient and stable OER. It is investigated that the NiFeZn support exhibits abundant defect sites and unsaturated coordination sites. These sites function to anchor and stabilize single Ir single atoms on the support. The strong synergetic electronic interaction between the Ir single atoms and the NiFeZn matrix resulted in remarkable OER performance of the as-fabricated Ir-SAC/NiFeZn catalyst. With a loading Ir content of 1.09 wt.%, this catalyst demonstrates a highly stable OER activity, with an overpotential of 196 mV at 10 mA·cm⁻² and a small Tafel slope of 35 mV·dec⁻¹ for the OER in a 1 M KOH solution. These results significantly surpass the performance of the commercially available IrO₂ catalyst.

Co₃O₄ is considered as one of promising cathode catalysts for lithium oxygen (Li-O₂) batteries, which contains both tetrahedral Co²⁺ sites (Co²⁺_Td) and octahedral Co³⁺ sites (Co³⁺_Oh). It is important to reveal the effect of optimal geometric configuration and oxidation state of cobalt ion in Co₃O₄ to improve the performance of Li-O₂ batteries. Herein, through regulating the synthesis process, Co²⁺ and Co³⁺ sites in Co₃O₄ were replaced with Zn and Al atoms to form materials with a unique Co site. The Li-O₂ batteries based on ZnCo₂O₄ showed longer cycle life than that of CoAl₂O₄, suggesting that in Co₃O₄, the Co³⁺_Oh site is a relatively better geometric configuration than Co²⁺_Td site for Li-O₂ batteries. Theoretical calculations revealed that Co³⁺_Oh sites provide higher catalysis activity, regulating the adsorption energy of the intermediate LiO₂ and accelerating the kinetics of the reaction in batteries, which further leads to the change of the morphology of the discharge product and ultimately improves the electrochemical performance of the batteries.

Regulating the coordination environment of transition-metal based materials in the axial direction with heteroatoms has shown great potential in boosting the oxygen reduction reaction (ORR). The coordination configuration and the regulation method are pivotal and elusive. Here, we report a combined strategy of matrix-activization and controlled-induction to modify the CoN₄ site by axial coordination of Co–S (Co₁N₄-S₁), which was validated by the aberration-corrected electron microscopy and X-ray absorption fine structure analysis. The optimal Co₁N₄-S₁ exhibits an excellent alkaline ORR activity, according to the half-wave potential (0.897 V vs. reversible hydrogen electrode (RHE)), Tafel slope (24.67 mV/dec), and kinetic current density. Moreover, the Co₁N₄-S₁ based Zn-air battery displays a high power density of 187.55 mW/cm² and an outstanding charge–discharge cycling stability for 160 h, demonstrating the promising application potential. Theoretical calculations indicate that the better regulation of CoN₄ on electronic structure and thus the highly efficient ORR performance can be achieved by axial Co–S.

Large scale synthesis of high-efficiency bifunctional electrocatalyst based on cost-effective and earth-abundant transition metal for overall water splitting in the alkaline environment is indispensable for renewable energy conversion. In this regard, meticulous design of active sites and probing their catalytic mechanism on both cathode and anode with different reaction environment at molecular- scale are vitally necessary. Herein, a coordination environment inheriting strategy is presented for designing low-coordination Ni²⁺ octahedra (L-Ni-8) atomic interface at a high concentration (4.6 at.%). Advanced spectroscopic techniques and theoretical calculations reveal that the self-matching electron delocalization and localization state at L-Ni-8 atomic interface enable an ideal reaction environment at both cathode and anode. To improve the efficiency of using the self-modification reaction environment at L-Ni-8, all of the structural features, including high atom economy, mass transfer, and electron transfer, are integrated together from atomic-scale to macro-scale. At high current density of 500 mA/cm², the samples synthesized at gram-scale can deliver low hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) overpotentials of 262 and 348 mV, respectively.

For electrocatalytic reduction of CO₂ to CO, the stabilization of intermediate COOH^* and the desorption of CO^* are two key steps. Pd can easily stabilize COOH^*, whereas the strong CO^* binding to Pd surface results in severe poisoning, thus lowering catalytic activity and stability for CO₂ reduction. On Ag surface, CO^* desorbs readily, while COOH^* requires a relatively high formation energy, leading to a high overpotential. In light of the above issues, we successfully designed the PdAg bimetallic catalyst to circumvent the drawbacks of sole Pd and Ag. The PdAg catalyst with Ag-terminated surface not only shows a much lower overpotential (-0.55 V with CO current density of 1 mA/cm²) than Ag (-0.76 V), but also delivers a CO/H₂ ratio 18 times as high as that for Pd at the potential of -0.75 V vs. RHE. The issue of CO poisoning is significantly alleviated on Ag-terminated PdAg surface, with the stability well retained after 4 h electrolysis at -0.75 V vs. RHE. Density functional theory (DFT) calculations reveal that the Ag-terminated PdAg surface features a lowered formation energy for COOH^* and weakened adsorption for CO^*, which both contribute to the enhanced performance for CO₂ reduction.

We developed a strategy based on coordination polymer to synthesize singleatom site Fe/N and S-codoped hierarchical porous carbon (Fe₁/N, S-PC). The as-obtained Fe₁/N, S-PC exhibited superior oxygen reduction reaction (ORR) performance with a half-wave potential (E_1/2, 0.904 V vs. RHE) that was better than that of commercial Pt/C (E_1/2, 0.86 V vs. RHE), single-atom site Fe/N-doped hierarchical porous carbon (Fe₁/N-PC) without S-doped (E_1/2, 0.85 V vs. RHE), and many other nonprecious metal catalysts in alkaline medium. Moreover, the Fe₁/N, S-PC revealed high methanol tolerance and firm stability. The excellent electrocatalytic activity of Fe₁/N, S-PC is attributed to the synergistic effects from the atomically dispersed porphyrin-like Fe-N₄ active sites, the heteroatom codoping (N and S), and the hierarchical porous structure in the carbon materials. The calculation based on density functional theory further indicates that the catalytic performance of Fe₁/N, S-PC is better than that of Fe₁/N-PC owing to the sulfur doping that yielded different rate-determining steps.

Downsizing to sub-nm is a general strategy to reduce the cost of catalysts. However, theoretical Wulff-constructed model suggests that sub-nm clusters show little activity for various reactions such as ammonia decomposition and ammonia synthesis because of the lack of active sites. As clusters may deviate from the ideal model construction under reaction conditions, a host–guest strategy to synthesize thermally stable 1.0 nm monodispersed Ru clusters by the pyrolysis of MIL-101 hosts is reported here to verify the hypothesis. For ammonia decomposition, the activity of the Ru clusters is 25 times higher than that of commercial Ru/active carbon (AC) at full-conversion temperature, while for ammonia synthesis, the activity of the Ru clusters is 500 times as high as that of promoted Ru NPs counterpart. The catalyst also maintains its activities for 40 h without any increase in the size. This model can be used to develop a host–guest strategy for designing thermally stable sub-nm clusters to atomic–efficiently catalyze reactions.

Electronic adjustment is one of the most commonly used strategies to improve the catalytic performance of heterogeneous catalysts. We prepared hexagonal ultrathin Pd nanosheets with edges modified by gold nanoparticles (Au@Pd nanosheets) using galvanic replacement method. By virtue of the electronic interactions between the Pd nanosheets and Au nanoparticles, the Au@Pd nanosheets exhibited excellent catalytic performances in the carbonylation of iodobenzene by carbon monoxide. The novel nanocomposites could be applied as model catalysts to explore electronic effects in catalysis.

We report a highly efficient Pd/Ni(OH)₂ catalyst loaded with ultra-low levels of palladium (50 ppm Pd by mass) for the selective hydrogenation of acetylene to ethylene. The turnover frequency for acetylene conversion over the 0.005% Pd/Ni(OH)₂ catalyst is twice that of the equivalent 0.8% Pd/Ni(OH)₂ catalyst. Notably, an acetylene-to-ethylene selectivity of 80% was achieved over a wide range of temperatures. Aberration-corrected high-angle annular dark-field scanning transmission electron microscopy was used to reveal the atomically dispersed nature of palladium in the 0.005% Pd/Ni(OH)₂ catalyst. The excellent selectivity of this catalyst is attributed to its atomically dispersed Pd sites, while the abundant hydroxyl groups of the support significantly enhance the acetylene conversion activity. This work opens up innovative opportunities for new types of highly efficient catalysts with trace noble-metal loadings for a wide variety of reactions.

An efficient, controllable, and facile two-step synthetic strategy to prepare graphene-based nanocomposites is proposed. A series of Fe₃O₄-decorated reduced graphene oxide (Fe₃O₄@RGO) nanocomposites incorporating Fe₃O₄ nanocrystals of various sizes were prepared by an ethanothermal method using graphene oxide (GO) and monodisperse Fe₃O₄ nanocrystals with diameters ranging from 4 to 10 nm. The morphologies and microstructures of the as-prepared composites were characterized by X-ray diffraction, Raman spectroscopy, nitrogen adsorption measurements, and transmission electron microscopy. The results show that GO can be reduced to graphene during the ethanothermal process, and that the Fe₃O₄ nanocrystals are well dispersed on the graphene sheets generated in the process. The analysis of the electrochemical properties of the Fe₃O₄@RGO materials shows that nanocomposites prepared with Fe₃O₄ nanocrystals of different sizes exhibit different electrochemical performances. Among all samples, Fe₃O₄@RGO prepared with Fe₃O₄ nanocrystals of 6 nm diameter possessed the highest specific capacitance of 481 F/g at 1 A/g, highlighting the excellent capability of this material. This work illustrates a promising route to develop graphene-based nanocomposite materials with a wide range of potential applications.