Showing papers by "Yunchen Du published in 2022"

Crystalline-Amorphous Ni2 P4 O12 /NiMoOx Nanoarrays for Alkaline Water Electrolysis: Enhanced Catalytic Activity via In Situ Surface Reconstruction.

Abstract: Water electrolysis affords a promising approach to large-scale hydrogen yield, but its efficiency is restrained by the sluggish water dissociation kinetics. Here, an efficient bifunctional electrocatalyst of in situ formed crystalline nickel metaphosphate on amorphous NiMoOx nanoarrays supported on nickel foam (c-Ni2 P4 O12 /a-NiMoOx /NF) for both hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) in alkaline solution is reported. The c-Ni2 P4 O12 /a-NiMoOx /NF can deliver a current density of 10 mA cm-2 at a low potential of 78 mV for HER, and a current density of 20 mA cm-2 at an overpotential of 250 mV for OER. Moreover, it only requires a small cell voltage of 1.55 V at 10 mA cm-2 for robust water splitting with outstanding long-term durability over 84 h. Various spectroscopic studies reveal that in situ surface reconstruction is crucial for the enhanced catalytic activity, where c-Ni2 P4 O12 /a-NiMoOx is transformed into c-Ni2 P4 O12 /a-NiMoO4 during the HER process, and into c-Ni2 P4 O12 /a-NiOOH in the OER process. This work may provide a new strategy for uncovering the catalytic mechanism of crystalline-amorphous catalysts.

Oxygen Vacancy-Induced Construction of CoO/h-TiO2 Z-Scheme Heterostructures for Enhanced Photocatalytic Hydrogen Evolution.

Abstract: Environmentally friendly catalysts with excellent performance and low cost are critical for photocatalysis. Herein, using hydrogenated TiO2 (h-TiO2) nanosheets with enriched oxygen vacancies as the support, two-dimensional CoO/h-TiO2 Z-scheme heterostructures are fabricated for hydrogen production through photocatalytic water splitting. It is revealed that the oxygen vacancies in h-TiO2 can inhibit the oxidation of Co2+ into high-valence Co3+ during the hydrothermal reaction and thermal treatment processes. A CoO/h-TiO2 Z-scheme heterostructure possesses a space charge region and a built-in electric field at the interface, and oxygen vacancies in h-TiO2 can provide more reactive sites, which synergistically improve the separation and transportation of photogenerated carriers. As a result, the photocatalytic hydrogen evolution rate achieves 129.75 μmol·h-1 (with 50 mg of photocatalysts) on the optimized CoO/h-TiO2 heterostructures. This work provides a new design idea for the preparation of excellent TiO2-based photocatalysts.

In Situ Growth of Nitrogen-Doped Carbon Nanotubes Based on Hierarchical Ni@C Microspheres for High Efficiency Bisphenol A Removal through Peroxymonosulfate Activation.

Abstract: N-doped carbon nanotubes (NCNTs) are promising metal-free heterogeneous catalysts toward peroxymonosulfate (PMS) activation in advanced oxidation processes for wastewater remediation. However, conventional CNTs always suffer from serious agglomeration and low N content, which renders their design synthesis as an important topic in the related field. With hierarchical Ni@C microspheres as a nutritious platform, we have successfully induced in situ growth of NCNTs on their surface by feeding melamine under high-temperature inert atmospheres. These as-grown NCNTs with a small diameter (ca. 20 nm) are firmly rooted in Ni@C microspheres and present loose accumulation on their surface, and their relative content can be tailored easily by manipulating the mass ratio of melamine to Ni@C microspheres. The investigation on bisphenol A (BPA) removal reveals that the loading amount of NCNTs affects the catalytic performance greatly, and the optimum ratio of melamine to Ni@C microspheres is 5.0 because the corresponding MNC-5.0 possesses sufficient surface N sites and moderate electron transfer, resulting in powerful PMS activation and sufficient utilization of reactive oxidative species (ROS). MNC-5.0 also addresses its advantages as compared with other NCNTs from post treatment and spontaneous growth strategies. The primary ROS responsible for BPA degradation are identified as hydroxyl radical, sulfate radical, superoxide radical, and singlet oxygen through quenching experiments and electron paramagnetic resonance, and the corresponding catalytic mechanism is also put forward based on these results.

Advances in Carbon-Based Microwave Absorbing Materials

Abstract: Electromagnetic (EM) pollution has been evolving as one of the most concerning environmental problems in current society, due to the extensive application of EM technology, from household electronic apparatuses to wireless base stations, as well as military radars [...].

Unveiling the Coercivity-Induced Electrocatalytic Oxygen Evolution Activity of Single-Domain CoFe2O4 Nanocrystals under a Magnetic Field.

Abstract: Spin polarization modulation in ferromagnetic materials has become an effective way to promote the electrocatalytic oxygen evolution reaction (OER). Herein, to reveal the coercivity-related OER performance, single-domain ferromagnetic CoFe2O4 (CFO) nanocrystals with different coercivities are synthesized and subjected to OER under an in situ tunable magnetic field. As the more ordered spin polarization state of CFO with a higher coercivity can afford a facilitated electron transfer process, the magnetic field-assisted OER activity can be more improved with an increase in coercivity. Specifically, the decreased magnitudes of the overpotential, Tafel slope, and charge transfer resistance increase on the samples with higher coercivity. The CFO with the largest coercivity (7500 Oe) shows the best OER performance with an overpotential of 350 mV at a current density of 10 mA cm-2 under a magnetic field of 14000 G. In addition, a hysteresis effect that maintains enhanced OER current density after the magnetic field has been withdrawn is observed, where higher coercivity affords a longer hysteresis period. The exploration of coercivity-related OER enhancement may provide new insights into the design and synthesis of promising "magnetic effect" catalysts.

Construction of plasmonic 1T-WS2/2H-WS2/CdS heterostructures for enhanced solar driven hydrogen evolution

Abstract: Localized surface plasmon resonance (LSPR) has been approved as a distinguished approach to improving the light absorption and carrier migration of photocatalysts. Herein, taking advantage of the LSPR effect of...