Research Article Issue
Composition-dependent micro-structure and photocatalytic performance of g-C3N4 quantum dots@SnS2 heterojunction
Nano Research 2021, 14 (11): 4188-4196
Published: 01 March 2021

Semiconductor combination is one of the most common strategies to obtain high-efficiency photocatalysts; however, the effect mechanism of composition ratio on micro-structure and photocatalytic activity is remaining unclear. In this study, a case of g-C3N4 quantum dots@SnS2 (CNQDn@SnS2) heterojunction with different ratio of CNQD is used to uncover the origin of optimum and excess composition for photocatalysts. Research on the functional mechanism of the optimum composition shows that 0.8 wt.% CNQD are completely attached to the non-(001) facets of SnS2, which benefits the formation of type-II heterojunction, resulting in an optimal pollutant degradation and mineralization efficiency. For the excess composition, both experiments and theoretical calculations confirm that excess CNQD (the part exceeding of 0.8 wt.%) located on the (001) facet of SnS2, leading to the type-I band alignment of this heterojunction, which severely restricts the separation of photo-induced charge carriers, and thus reduces their lifetime. This work makes the functional mechanism of composition ratio on micro-structure and photocatalytic activity clearer. Related research results provide a new insight into semiconductor combination study and take an important step toward the rational design of highly active photocatalysts.

Research Article Issue
Unconventional dual-vacancies in nickel diselenide-graphene nanocomposite for high-efficiency oxygen evolution catalysis
Nano Research 2020, 13 (12): 3292-3298
Published: 22 August 2020

Although nickel-based catalysts display good catalytic capability and excellent corrosion resistance under alkaline electrolytes for water splitting, it is still imperative to enhance their activity for real device applications. Herein, we decorated Ni0.85Se hollow nanospheres onto reduced graphene oxide (RGO) through a hydrothermal route, then annealed this composite at different temperatures (400 °C, NiSe2-400 and 450 °C, NiSe2-450) under argon atmosphere, yielding a kind of NiSe2/RGO composite catalysts. Positron annihilation spectra revealed two types of vacancies formed in this composite catalyst. We found that the NiSe2-400 catalyst with dual Ni-Se vacancies is able to catalyze the oxygen evolution reaction (OER) efficiently, needing a mere 241 mV overpotential at 10 mA·cm-2. In addition, this catalyst exhibits outstanding stability. Computational studies show favorable energy barrier on NiSe2-400, enabling moderate OH- adsorption and O2 desorption, which leads to the enhanced energetics for OER.

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