Synergistic etching of nickel foam by Fe3+ and Cl- ions to synthesize nickel-iron-layered double hydroxide nanolayers with abundant oxygen vacancies for superior urea oxidation.

Urea electrolysis is an appealing topic for hydrogen production due to its ability to extract hydrogen at a lower potential. However, it is plagued by sluggish kinetics and noble-metal catalyst requirements. Herein, we developed nickel-iron-layered double hydroxide (NiFe-LDH) nanolayers with abundant oxygen vacancies (OV) via synergistically etching nickel foam with Fe3+ and Cl- ions, enabling the efficient conversion of urea into H2 and N2. The synthesized OV-NiFe-LDH exhibits a lower potential (1.30 vs. reversible hydrogen electrode, RHE) for achieving 10 mA cm-2 in the urea oxidation reaction (UOR), surpassing most recently reported Ni-based electrodes. OV provides favorable conductivity and a large surface area, which results in a 4.1-fold in electron transport and a 5.1-fold increase in catalyst reactive sites. Density Functional Theory (DFT) calculations indicate that OV can lower the adsorption energy of urea, and enhance the bonding strength of *CONHNH, giving rise to improved UOR. This study provides a viable path toward economical and efficient production of high-purity hydrogen.

Synergistic catalysis of TiO2/WO3 photoanode and Sb-SnO2 electrode with highly efficient ClO• generation for urine treatment.

Urine is the major source of nitrogen pollutants in domestic sewage and is a neglected source of H2. Although ClO• is used to overcome the poor selectivity and slow kinetics of urea decomposition, the generation of ClO• suffers from the inefficient formation reaction of HO• and reactive chlorine species (RCS). In this study, a synergistic catalytic method based on TiO2/WO3 photoanode and Sb-SnO2 electrode efficiently producing ClO• is proposed for urine treatment. The critical design is that TiO2/WO3 photoanode and Sb-SnO2 electrode that generate HO• and RCS, respectively, are assembled in a confined space through face-to-face (TiO2/WO3//Sb-SnO2), which effectively strengthens the direct reaction of HO• and RCS. Furthermore, a Si solar panel as rear photovoltaic cell (Si PVC) is placed behind TiO2/WO3//Sb-SnO2 to fully use sunlight and provide the driving force of charge separation. The composite photoanode (TiO2/WO3//Sb-SnO2 @Si PVC) has a ClO• generation rate of 260% compared with the back-to-bake assembly way. In addition, the electrons transfer to the NiFe LDH@Cu NWs/CF cathode for rapid H2 production by the constructed photoelectric catalytic (PEC) cell without applied external biasing potential, in which the H2 production yield reaches 84.55 µmol h-1 with 25% improvement of the urine denitrification rate. The superior performance and long-term stability of PEC cell provide an effective and promising method for denitrification and H2 generation.

0D/3D coupling of g-C3N4 QDs/hierarchical macro-mesoporous CuO-SiO2 for high-efficiency norfloxacin removal in photo-Fenton-like processes.

Photo-Fenton process is an advanced oxidation technology, which is used to eliminate organic pollutants in environmental pollution. In this paper, g-C3N4 quantum dots incorporated hierarchical macro-mesoporous CuO-SiO2 (MM SC-QDs) composite was successfully fabricated by a dual-template method combined with polystyrene sphere (PS) crystal and copolymer F127. With the presence of H2O2, MM SC-QDs exhibited excellent degradation performance against the antibiotic pollutant norfloxacin (NOR) under visible-light assisted heterogeneous Fenton process at neutral condition, which was 27 times higher than that of the Bulk CuO-SiO2. Interconnected macropores, together with abundant mesopores effectively expand specific surface area and improve mass transfer. In addition, the g-C3N4 QDs served as the separation center for photogenerated charges, promoting the separation and migration of the charge carriers. Wherein, the long-lived photogenerated electrons were effectively separated and transferred to the surface of CuO-SiO2, which accelerated the reduction rate of Cu2+ to Cu+, enhancing the photo-Fenton-like catalytic activity. This stable, efficient, and environmentally friendly Cu-based heterogeneous photo-Fenton-like catalyst is expected to become an effective implementation in organic pollution removal. Meanwhile, this paper proves that Cu-based materials can activate H2O2 to generate singlet oxygen (1O2) for the degradation of organic pollutants. The transformation mechanism of 1O2 was clarified, which is helpful to better understand the Fenton-like reaction process of Cu-based materials.