Sort:
Research Article Issue
Polyoxometalates for continuous power generation by atmospheric humidity
Nano Research 2024, 17 (3): 1875-1885
Published: 01 August 2023
Downloads:199

Atmospheric humidity is a sustainable low-value energy widely existing in natural environment, which is a promising candidate to solve the noncontinuous and low efficiency of low-value energy power generation. Here the mono-substituted Dawson-type polyoxometalates are constructed to be highly dispersed organic ammonium-polyoxoanion clusters and are assembled into thin films power generators with micropores, working in atmospheric humidity. The optimal polyoxometalates generator with the thickness of 7.2 μm and the area of 0.36 cm2 produces a voltage of 0.68 V and a current density of 19.5 μA·cm−2 under simulated natural environment, and works continuously and stably under almost all-natural environments (humidity 10%–90%). The highly dispersed polyoxometalate nanoclusters can form microporous in polyoxometalate films to effectively absorb atmospheric humidity and spontaneously form distribution gradient of water, which is the structural basis of power generation. The continuous power generation may be maintained by the effective adsorption and utilization of H2O, the huge electrostatic field of organic ammonium-polyoxoanion clusters, and the reasonably designed polyoxometalates containing inorganic small ions with high mobility. It is the first humidity generator designed with polyoxometalates, which may provide a new research direction for polyoxometalates in sustainable utilization of low-value energy.

Open Access Research Article Issue
Grain boundaries passivation of high efficiency and stable perovskite photodetector by polyoxometalate-based composite SiW11@ZIF-8
Polyoxometalates 2022, 1 (1): 9140003
Published: 25 August 2022
Downloads:461

Polyoxometalates (POMs) can enable energy level tuning to match perovskite layers. They are considered electronic bridges to modify perovskite and improve the performance of photovoltaic devices. Therefore, in the present work, we dispersed the vacancy POMs K8[α-SiW11O39]·H2O ({SiW11}) in the metal-organic frameworks (MOFs) to modify the perovskite layer. {SiW11} could adjust the energy level between the layers of the perovskite photodetector. Moreover, the hydrogen bonds formed between SiW11@ZIF-8 and perovskite effectively passivated the grain boundaries (GBs) of the perovskite layer. X-ray diffraction spectroscopy (XRD) showed that the crystallinity of perovskite was significantly improved. In addition, scanning electron microscopy (SEM) images demonstrated that the average size of perovskite grains increased from 254.50 to 719.27 nm, proving the effective passivation of the GBs. Furthermore, a series of tests such as infrared spectroscopy (IR), N2 adsorption/desorption isotherms, transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS) also proved that {SiW11} could be successfully loaded into the pores of ZIF-8 through electrostatic interactions. The photocurrent of the SiW11@ZIF-8 doped device reached 41.95 μA, about three times as high as that of the blank device (14.41 μA). Also, under unencapsulated conditions, it could still maintain more than 90% stability for nearly 700 h. This work demonstrates the potential application of POM@MOF-type composites in the field of perovskite photodetectors.

Research Article Issue
A strategy for highly dispersed Mo2C/MoN hybrid nitrogen-doped graphene via ion-exchange resin synthesis for efficient electrocatalytic hydrogen reduction
Nano Research 2018, 11 (9): 4535-4548
Published: 16 March 2018
Downloads:13

Molybdenum carbide/molybdenum nitride hybrid N-doped graphene (abbreviated as Mo2C/MoN/NG), as an efficient electrocatalyst for the hydrogen evolution reaction (HER), was synthesized via simple ion-exchange resin synthesis followed by a two-step annealing process, which increased the dispersion degree of the electrocatalyst's active sites on the support skeleton and simplified the synthetic conditions. Additionally, N-doped graphene (NG) enhanced the electron transfer and reduced the inner resistance. The material has a graphene-like morphology and highly dispersed Mo2C/MoN nanoparticles about 2 nm in diameter on the NG. X-ray photoelectron spectroscopy, X-ray diffraction, and high-resolution transmission electron microscopy revealed that Mo2C/MoN/NG consisted of Mo2C and MoN composited together. Finally, Mo2C/MoN/NG exhibited remarkable performance as an electrocatalyst for the HER with a small overpotential of 78.82 mV and a small Tafel slope of 39.3 mV·dec-1 in a 0.5 mol·L-1 H2SO4 solution. Its activity was approximately 30% lower than that of 20% Pt/C and 60% higher than that of NG. Also, it exhibited a low onset overpotential of 24.82 mV, which is similar to the theoretical HER potential. Our work provides a foundation for advanced HER applications of molybdenum compounds.

total 3