Facile, Controllable, and Ultrathin NiFe-LDH In Situ Grown on a Ni Foam by Ultrasonic Self-Etching for Highly Efficient Urine Conversion

As the primary source of nitrogen pollutants in domestic sewage, urine is also an alternative for H₂ production via electrochemical processes. However, it suffers from sluggish kinetics and noble-metal catalyst requirement. Here, we report a non-precious ultrathin NiFe-layered double hydroxide catalyst for the remarkable conversion of urea into N₂ and H₂, which is in situ grown on a Ni foam via ultrasonic self-etching in Fe³⁺/ethylene glycol (EG). EG regulates the etching rate of Fe³⁺, resulting in an ultrathin nanosheet structure with the aid of ultrasonication. This structure dramatically promotes the dehydrogenation process via decreasing the nanolayer thickness from 120 to 3.4 nm and leads to a 4.8-fold increase in the generation of active sites. It exhibits record urea oxidation kinetics (390.8 mA·cm^-2 at 1.5 V vs RHE) with excellent stability (120 h), which is 11.8 times better than that of commercial Pt/C catalyst (33.1 mA·cm^-2). Tests with real urine at 20 mA cm^-2 achieve 74% total nitrogen removal and 2853 μmol·h^-1 of H₂ production. This study provides an attractive landscape for producing H₂ by consuming urine biowastes.

Lattice Compressive Strain of Co3O4 Induced by Synthetic Solvents Promotes Efficient Oxidation of Benzene at Low Temperature

A series of Co₃O₄ with different surface defective structures were prepared by the solvothermal method and tested for the activity of benzene oxidation. The characterizations revealed that the synthetic solvent had a dramatic effect on the composition of Co₃O₄ precursors as well as the physicochemical properties of Co₃O₄. Although all Co₃O₄ exhibited a cubic spinel structure, Co₃O₄ prepared with triethylene glycol (Co-TEG) had the highest compressive strain due to the nature of high viscosity of triethylene glycol. These in turn affected the surface chemical structure and the low-temperature redox properties. Co-TEG exhibited the best benzene oxidation activity and showed excellent stability and good water resistance. In situ diffuse reflectance infrared Fourier transform spectroscopy was used to study the oxidation process of benzene. It was found that Co-TEG with more defective structures had abundant surface adsorbed oxygen and active lattice oxygen, which promoted the conversion of benzene and the corresponding intermediates at low temperature.

Galvanic displacement assembly of ultrathin Co3O4 nanosheet arrays on nickel foam for a high-performance supercapacitor

High-performance supercapacitors are very desirable for many portable electronic devices, electric vehicles and high-power electronic devices. Herein, a facile and binder-free synthesis method, galvanic displacement of the precursor followed by heat treatment, is used to fabricate ultrathin Co₃O₄ nanosheet arrays on nickel foam substrate. When used as a supercapacitor electrode the prepared Co₃O₄ on nickel foam exhibits a maximum specific capacitance of 1095 F g^-1 at a current density of 1 A g^-1 and good cycling stability of 71% retention after 2000 cycling tests. This excellent electrochemical performance can be ascribed to the high specific surface area of each Co₃O₄ nanosheet that comprises numerous nanoparticles.