Catalase Mimic Property of Co₃O₄ Nanomaterials with Different Morphology and Its Application as a Calcium Sensor

The applications of inorganic nanomaterials as biomimetic catalysts are receiving much attention because of their high stability and low cost. In this work, Co₃O₄ nanomaterials including nanoplates, nanorods, and nanocubes were synthesized. The morphologies and compositions of the products were characterized by scanning electron microscopy, transmission electron microscopy, and X-ray diffraction. The catalytic properties of Co₃O₄ nanomaterials as catalase mimics were studied. The Co₃O₄ materials with different morphology exhibited different catalytic activities in the order of nanoplates > nanorods > nanocubes. The difference of the catalytic activities originated from their different abilities of electron transfer. Their catalytic activities increased significantly in the presence of calcium ion. On the basis of the stimulation by calcium ion, a biosensor was constructed by Co₃O₄ nanoplates for the determination of calcium ion. The biosensor had a linear relation to calcium concentrations and good measurement correlation between 0.1 and 1 mM with a detection limit of 4 μM (S/N = 3). It showed high selectivity against other metal ions and good reproducibility. The proposed method was successfully applied for the determination of calcium in a milk sample

Three-Dimensional Hierarchical Nickel Cobalt Phosphide Nanoflowers as an Efficient Electrocatalyst for the Hydrogen Evolution Reaction under Both Acidic and Alkaline Conditions

The sustainable hydrogen fuel from water electrolysis demands the development of efficient and robust non-noble electrocatalysts for the hydrogen evolution reaction (HER). Tuning the morphology and chemical composition is paramount to constructing electrocatalysts with superior activity and stability. In this work, novel ternary nickel-doped cobalt phosphide (Ni–Co–P) nanoflowers assembled by porous and unltrathin nanosheets were first prepared by a facile solvothermal reaction following a phosphidation procedure. The Ni–Co–P nanoflowers exhibited remarkable electrocatalytic HER performance, exhibiting overpotentials of as low as 83 and 92 mV at 10 mA cm^–2 and small Tafel slopes of 46.6 and 49.6 mV dec^–1 under1 M KOH and 0.5 M H₂SO₄ conditions, respectively, which was one of the most active earth-abundant electrocatalysts. Additionally, the electrocatalysts exhibited high durability for HER under both alkaline and acidic conditions. Various techniques further demonstrated that the superior activity of Ni–Co–P nanoflowers was attributed to the unique 3D hierarchical morphology and the modified electron structure due to Ni incorporation. The superior activity and stability of novel Ni–Co–P nanoflowers hold promising potential for applications in the production of hydrogen fuel from water splitting