Metastable metal oxides with ribbon morphologies have promising applications for energy conversion catalysis, however they are largely restricted by their limited synthesis methods. In this study, a monoclinic phase iridium oxide nanoribbon with a space group of C2/m is successfully obtained, which is distinct from rutile iridium oxide with a stable tetragonal phase (P42/mnm). A molten-alkali mechanochemical method provides a unique strategy for achieving this layered nanoribbon structure via a conversion from a monoclinic phase K0.25IrO2 (I2/m (12)) precursor. The formation mechanism of IrO2 nanoribbon is clearly revealed, with its further conversion to IrO2 nanosheet with a trigonal phase. When applied as an electrocatalyst for the oxygen evolution reaction in acidic condition, the intrinsic catalytic activity of IrO2 nanoribbon is higher than that of tetragonal phase IrO2 due to the low d band centre of Ir in this special monoclinic phase structure, as confirmed by density functional theory calculations.
Designing well-ordered nanocrystal arrays with subnanometre distances can provide promising materials for future nanoscale applications. However, the fabrication of aligned arrays with controllable accuracy in the subnanometre range with conventional lithography, template or self-assembly strategies faces many challenges. Here, we report a two-dimensional layered metastable oxide, trigonal phase rhodium oxide (space group, P-3m1 (164)), which provides a platform from which to construct well-ordered face-centred cubic rhodium nanocrystal arrays in a hexagonal pattern with an intersurface distance of only 0.5 nm. The coupling of the well-ordered rhodium array and metastable substrate in this catalyst triggers and improves hydrogen spillover, enhancing the acidic hydrogen evolution for H2 production, which is essential for various clean energy-related devices. The catalyst achieves a low overpotential of only 9.8 mV at a current density of −10 mA cm−2, a low Tafel slope of 24.0 mV dec−1, and high stability under a high potential (vs. RHE) of −0.4 V (current density of ~750 mA cm−2). This work highlights the important role of metastable materials in the design of advanced materials to achieve high-performance catalysis.
Metallic
molybdenum sulfide (1T-MoS2) is considered
as the most promising electrocatalyst for the acidic hydrogen evolution
reaction (HER). Nevertheless, exploring a facile and effective approach
for achieving high-purity 1T-MoS2 is still full of challenges.
Herein, we demonstrate a two-dimensional material-assisted confined
synthetic strategy, as an available method to construct and stabilize
1T-MoS2. During the hydrothermal process, the interaction
between the N source and MoS2 is largely enhanced in a
two-dimensional confined reactor, formed by reduced graphene oxides,
successfully obtaining a high concentration of 90.1% of 1T-MoS2, named N-MoS2/rGO. The optimal N-MoS2/rGO nanosheets require a low overpotential (130 mV) to reach a current
density of 10 mA·cm–2 and a low Tafel slope
of 46.5 mV·dec–1. Additionally, they also exhibit
high stability for at least 12 h in an acidic electrolyte maintaining
84.2% of the 1T-MoS2 phase. This work opens up an avenue
to construct two-dimensional metastable materials for advanced catalysis.
Sonodynamic therapy (SDT) triggered by ultrasound (US) can overcome pivotal limitations of photo-therapy owing to its high depth-penetration and low phototoxicity. However, there is still a need to develop more efficient sonosensitizes to enhance the therapy efficiency.
Methods:
In this study, Pt nanoparticles (Pt NPs) are reduced on silicon nanowires (SiNWs) by
in situ
reduction to prepare Si-Pt nanocomposites (Si-Pt NCs).
Results:
Si-Pt NCs can produce reactive oxygen radicals (ROS) under ultrasound (US) irradiation, which have sonodynamic therapy (SDT) effect. Meanwhile, Si-Pt NCs can convert excess hydrogen peroxide (H
2
O
2
) into ROS in the tumor microenvironment, which endow strong chemodynamic therapy (CDT) effect. Taking the advantages of the mesoporous structure of SiNWs, the SDT and CDT effects of Si-Pt NCs are stronger than those of the pure Pt NPs and SiNWs. Besides, the mild photothermal effect of Si-Pt NCs further improves the SDT&CDT activity and realizes the combined cancer therapy.
Conclusion:
The developed Si-Pt NCs with the ability of photothermal enhanced SDT/CDT combined therapy play a momentous role in the novel cancer treatment.
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