Defect-Rich Ultrathin Cobalt–Iron Layered Double Hydroxide for Electrochemical Overall Water Splitting

Efficient and durable electrocatalysts from earth-abundant elements play a vital role in the key renewable energy technologies including overall water splitting and hydrogen fuel cells. Here, generally used CoFe based layered double hydroxides (LDHs) were first delaminated and exfoliated in the DMF-ethanol solvent (CoFe LDH-F), with enhancement both in oxygen evolution reaction (OER) and hydrogen evolution reaction (HER). The exfoliation process creates more coordinatively unsaturated metals and improves the intrinsic electronic conductivity, which is important in water electrolyzer reactions. In the basic solution, the CoFe LDH-F catalyst outperforms the commercial iridium dioxide (IrO₂) electrocatalyst in activity and stability for OER and approaches the performance of platinum (Pt) for HER. The bifunctional electrocatalysts can be further used for overall water splitting, with a current density of ∼10 mA/cm² at the applied voltage of 1.63 V for long-term electrolysis test, rivalling the performance of Pt and IrO₂ combination as benchmarks. Our findings demonstrate the promising catalytic activity of LDHs for scale-up alkaline water splitting

Bimetallic Oxide of Y₂Cu₂O₅ for Electroreduction of CO₂ to Syngas

The incorporation of guest elements into Cu-based bimetallic oxides has been proven as an effective way to modify the electronic structure and reactivity of Cu active sites. Here, the Y element was chosen as the guest element to modulate the electronic structure of Cu and alter its performance for electrochemical CO2 reduction reaction (CO2RR). Y2Cu2O5, a high-crystallinity Cu-based bimetallic oxide, was synthesized via the sol–gel method. For pure-phase CuO and Y2O3 controls, the selectivity of H2 significantly exceeded that of CO. While Y and Cu combined in equal molar weights to form Y2Cu2O5, a notable enhancement in the CO selectivity was observed, resulting in a CO/H2 ratio of approximately 1:1. These results prove that under the influence of Y, the electronic structure of Cu exhibits heightened CO selectivity. When the electrolyte solution was substituted with 1 M KOH, the CO/H2 ratio achieved was about 2:1, indicating that the ratio of syngas can be adjusted by changing the concentration or type of electrolyte. This study explores the electronic modulation of a guest element in Cu-based bimetallic oxides and clarifies the beneficial influence of the Y element on the activity of Cu sites, which provides a novel approach for designing and regulating the activity of catalyst active sites

1D/1D Hierarchical Nickel Sulfide/Phosphide Nanostructures for Electrocatalytic Water Oxidation

The sluggish kinetics of the oxygen evolution reaction (OER) limits the efficiencies of solar-powered electrical-conversion applications, such as water splitting and carbon dioxide reduction. Herein, we rationally designed a metallic nanostructured nickel sulfide/phosphide hybrid (NiS_<i>x</i>P_<i>y</i>) as an efficient precatalyst for OER, with one-dimensional (1D) nanowires grown on 1D nanorods. The resulting metallic hybrid NiS_<i>x</i>P_<i>y</i> catalyst can accelerate the electron transfer process and expose abundant in situ-generated NiOOH species during OER (NiS_<i>x</i>P_<i>y</i>–O). Therefore, NiS_<i>x</i>P_<i>y</i>–O exhibits a low overpotential of 192 mV (with 100% <i>iR</i> compensation; this value should be 200 mV without compensation) to achieve an O₂ partial current density (<i>j</i>_O2) of 10 mA cm^–2 and a robust stability over 135 h without obvious degradation. Moreover, a <i>j</i>_O2 of 10 mA cm^–2 at an overpotential of 315 mV (with 100% <i>iR</i> compensation; this value should be 365 mV without compensation) is attained in near-neutral conditions. These results may pave a new way to design metallic precatalysts with 1D/1D hierarchical nanostructures to boost the OER

Facile Fabrication of Large-Aspect-Ratio g‑C₃N₄ Nanosheets for Enhanced Photocatalytic Hydrogen Evolution

Exfoliation of bulk graphitic carbon nitride (BCN) into two-dimensional (2D) nanosheets is one of the effective strategies to improve its photocatalytic performance. Compared with BCN, the 2D g-C₃N₄ nanosheets (CNNS) have larger specific surface areas and more reaction sites. With the etching assistance of anhydrous ethylenediamine, BCN can be successfully peeled off into 2D CNNS with a large lateral size of more than 15 μm which is much larger than that of other works. After appropriate etch by anhydrous ethylenediamine, the specific surface area of g-C₃N₄ expands from 4.7 to 31.1 m² g^–1 and the photocatalytic hydrogen evolution rate increases 7.4 times, from 4.8 to 35.3 μmol h^–1. In contrast to other reported methods, the strategy to fabricate 2D CNNS in this work is convenient and it is the first time to report the fabrication of 2D CNNS with the assistance of alkaline reagent

Bimetallic Carbide as a Stable Hydrogen Evolution Catalyst in Harsh Acidic Water

Cheap, efficient, and stable hydrogen evolution reaction (HER) electrocatalysts have long been pursued, owing to their scientific and technological importance. Currently, platinum has been regarded as the benchmarked HER electrocatalyst. Unfortunately, the low abundance and high cost impede its industrial applications. Here, we synthesize bimetallic carbide Mo₆Ni₆C grown on nickel foam as a HER catalyst, delivering a low overpotential of −51 mV at −10 mA cm^–2 in 0.5 M H₂SO₄ for more than 200 h, which is among the best reported benchmarked HER catalysts in acid to date. On the basis of experimental observations and theoretical modeling, we ascribe the good activity to the proper Gibbs free energy of adsorbed hydrogen (Δ<i>G</i>(H*)) for the carbon active sites and attribute the stability to the corrosion-stable Mo–Mo bonds in the crystal structure. This work demonstrates the possibility for Mo₆Ni₆C to be one of the best candidates for HER electrocatalysts in the large-scale electrolysis industry

Bimetallic Carbide as a Stable Hydrogen Evolution Catalyst in Harsh Acidic Water

Cheap, efficient, and stable hydrogen evolution reaction (HER) electrocatalysts have long been pursued, owing to their scientific and technological importance. Currently, platinum has been regarded as the benchmarked HER electrocatalyst. Unfortunately, the low abundance and high cost impede its industrial applications. Here, we synthesize bimetallic carbide Mo₆Ni₆C grown on nickel foam as a HER catalyst, delivering a low overpotential of −51 mV at −10 mA cm^–2 in 0.5 M H₂SO₄ for more than 200 h, which is among the best reported benchmarked HER catalysts in acid to date. On the basis of experimental observations and theoretical modeling, we ascribe the good activity to the proper Gibbs free energy of adsorbed hydrogen (Δ<i>G</i>(H*)) for the carbon active sites and attribute the stability to the corrosion-stable Mo–Mo bonds in the crystal structure. This work demonstrates the possibility for Mo₆Ni₆C to be one of the best candidates for HER electrocatalysts in the large-scale electrolysis industry

Accelerating Neutral Hydrogen Evolution with Tungsten Modulated Amorphous Metal Hydroxides

Developing efficient, low-cost, and biocompatible electrocatalysts toward hydrogen evolution reaction (HER) in neutral environments is vital to the development of a hybrid water splitting–biosynthetic system to achieve high-efficiency solar-to-fuels conversion. We report here a strategy to improve the sluggish HER kinetics on 3d transition-metal hydroxides by incorporating tungsten through a one-step electrodeposition method. The prepared amorphous CoW­(OH)_<i>x</i> delivers high HER activity in neutral solution, which only requires overpotentials of −73.6 and −114.9 mV to achieve the current densities of −10 and −20 mA cm^–2 in 1.0 M phosphate buffer solution (PBS), respectively. The activity can be ascribed to the synergistic effects between Co and W, where Co sites facilitate H₂O dissociation to generate H_ad intermediates and W sites could effectively convert H_ad to H₂. Meanwhile, the amorphous architecture features homogeneously dispersed Co and W atoms that avoid crystalline phase separation, further strengthening their collaborative interactions. Similar enhanced HER activity is also observed on the electrodeposited NiW­(OH)_<i>x</i> electrocatalyst, suggesting the universality of this strategy for accelerating HER in neutral environments