Structure Effects of 2D Materials on α‑Nickel Hydroxide for Oxygen Evolution Reaction

To engineer low-cost, high-efficiency, and stable oxygen evolution reaction (OER) catalysts, structure effects should be primarily understood. Focusing on this, we systematically investigated the relationship between structures of materials and their OER performances by taking four 2D α-Ni­(OH)₂ as model materials, including layer-stacked bud-like Ni­(OH)₂-NB, flower-like Ni­(OH)₂-NF, and petal-like Ni­(OH)₂-NP as well as the ultralarge sheet-like Ni­(OH)₂-NS. For the first three (layer-stacking) catalysts, with the decrease of stacked layers, their accessible surface areas, abilities to adsorb OH^–, diffusion properties, and the intrinsic activities of active sites increase, which accounts for their steadily enhanced activity. As expected, Ni­(OH)₂-NP shows the lowest overpotential (260 mV at 10 mA cm^–2) and Tafel slope (78.6 mV dec^–1) with a robust stability over 10 h among the samples, which also outperforms the benchmark IrO₂ (360 mV and 115.8 mV dec^–1) catalyst. Interestingly, Ni­(OH)₂-NS relative to Ni­(OH)₂-NP exhibits even faster substance diffusion due to the sheet-like structure, but shows inferior OER activity, which is mainly because the Ni­(OH)₂-NP with a smaller size possesses more active boundary sites (higher reactivity of active sites) than Ni­(OH)₂-NS, considering the adsorption properties and accessible surface areas of the two samples are quite similar. By comparing the different structures and their OER behaviors of four α-Ni­(OH)₂ samples, our work may shed some light on the structure effect of 2D materials and accelerate the development of efficient OER catalysts

Tungsten-Doped Molybdenum Sulfide with Dominant Double-Layer Structure on Mixed MgAl Oxide for Higher Alcohol Synthesis in CO Hydrogenation

Improving the C₂+ alcohols selectivity is highly desirable for higher alcohols synthesis in CO hydrogenation. Herein, an effective method was developed for Mo-based supported catalysts by the combination of tungsten-doping and surfactant-assisted hydrothermal strategy. The tungsten-doping enhanced the interaction between Ni and W/Mo metal species to form more of the Ni-MoW-S phase with tunable slab size and stacking layers, and thus promoted the chain growth of alcohol to form a greater amount of higher alcohols in CO hydrogenation. The optimal K,Ni–Mo_0.75W_0.25/MMO-S exhibited a dominant double-layer structure (∼39.0%) and highly synergetic effects between Ni and W/Mo species, resulting in the highest total alcohol selectivity (76.1%) and in higher alcohols selectivity. This work provides a new route for tuning the morphology of MoS₂/WS₂ and synergetic effects between Ni and W/Mo species in supported catalysts to improve the selectivity of higher alcohols

Strongly Coupled FeNi Alloys/NiFe₂O₄@Carbonitride Layers-Assembled Microboxes for Enhanced Oxygen Evolution Reaction

Hydrogen produced from electrocatalytic water splitting is a promising route due to the sustainable powers derived from the solar and wind energy. However, the sluggish kinetics at the anode for water splitting makes the highly effective and inexpensive electrocatalysts desirable in oxygen evolution reaction (OER) by structure and composition modulations. Metal–organic frameworks (MOFs) have been intensively used as the templates/precursors to synthesize complex hollow structures for various energy-related applications. Herein, an effective and facile template-engaged strategy originated from bimetal MOFs is developed to construct hollow microcubes assembled by interconnected nanopolyhedron, consisting of intimately dominant FeNi alloys coupled with a small NiFe₂O₄ oxide, which was confined within carbonitride outer shell (denoted as FeNi/NiFe₂O₄@NC) via one-step annealing treatment. The optimized FeNi/NiFe₂O₄@NC exhibits excellent electrocatalytic performances toward OER in alkaline media, showing 10 mA·cm^–2 at η = 316 mV, lower Tafel slope (60 mV·dec^–1), and excellent durability without decay after 5000 CV cycles, which also surpasses the IrO₂ catalyst and most of non-noble catalysts in the OER, demonstrating a great perspective. The superior OER performance is ascribed to the hollow interior for fast mass transport, in situ formed strong coupling between FeNi alloys and NiFe₂O₄ for electron transfer, and the protection of carbonitride layers for long stability