Synergistic barium titanate/MXene composite as a high-performance piezo-photocatalyst for efficient dye degradation.

Piezo-photocatalysis combines photocatalysis and piezoelectric effects to enhance catalytic efficiency by creating an internal electric field in the photocatalyst, improving carrier separation and overall performance. This study presents a high-performance piezo-photocatalyst for efficient dye degradation using a synergistic barium titanate (BTO)-MXene composite. The composite was synthesized via a facile method, combining the unique properties of BTO nanoparticles with the high conductivity of MXene. The structural and morphological analysis confirmed the successful formation of the composite, with well-dispersed BTO nanoparticles on the MXene surface. The piezo-photocatalytic activity of the composite was evaluated using a typical dye solution (Rhodamine B: RhB) under ultraviolet irradiation and mechanical agitation. The results revealed a remarkable enhancement in dye degradation (90 % in 15 min for piezo-photocatalysis) compared to individual stimuli (58.2 % for photocatalysis and 95.8 % in 90 min for piezocatalysis), highlighting the synergistic effects between BTO and MXene. The enhanced catalytic performance was attributed to the efficient charge separation and transfer facilitated by the composite's structure, leading to increased reactive species generation and dye molecule degradation. Furthermore, the composite exhibited excellent stability and reusability, showcasing its potential for practical applications in wastewater treatment. Overall, this work represents a promising strategy for designing high-performance synergistic catalysts, addressing the pressing need for sustainable solutions in environmental remediation.

Angstrom-Confined Electrochemical Synthesis of Sub-Unit-Cell Non-Van Der Waals 2D Metal Oxides.

Bottom-up electrochemical synthesis of atomically thin materials is desirable yet challenging, especially for non-van der Waals (non-vdW) materials. Thicknesses below a few nanometers have not been reported yet, posing the question how thin can non-vdW materials be electrochemically synthesized. This is important as materials with (sub-)unit-cell thickness often show remarkably different properties compared to their bulk form or thin films of several nanometers thickness. Here, a straightforward electrochemical method utilizing the angstrom-confinement of laminar reduced graphene oxide (rGO) nanochannels is introduced to obtain a centimeter-scale network of atomically thin (<4.3 Å) 2D-transition metal oxides (2D-TMO). The angstrom-confinement provides a thickness limitation, forcing sub-unit-cell growth of 2D-TMO with oxygen and metal vacancies. It is showcased that Cr2 O3 , a material without significant catalytic activity for the oxygen evolution reaction (OER) in bulk form, can be activated as a high-performing catalyst if synthesized in the 2D sub-unit-cell form. This method displays the high activity of sub-unit-cell form while retaining the stability of bulk form, promising to yield unexplored fundamental science and applications. It is shown that while retaining the advantages of bottom-up electrochemical synthesis, like simplicity, high yield, and mild conditions, the thickness of TMO can be limited to sub-unit-cell dimensions.

Mass Transport via In-Plane Nanopores in Graphene Oxide Membranes.

Angstrom-confined solvents in 2D laminates can travel through interlayer spacings, through gaps between adjacent sheets, and via in-plane pores. Among these, experimental access to investigate the mass transport through in-plane pores is lacking. Our experiments allow an understanding of this mass transport via the controlled variation of oxygen functionalities, size and density of in-plane pores in graphene oxide membranes. Contrary to expectations, our transport experiments show that higher in-plane pore densities may not necessarily lead to higher water permeability. We observed that membranes with a high in-plane pore density but a low amount of oxygen functionalities exhibit a complete blockage of water. However, when water-ethanol mixtures with a weaker hydrogen network are used, these membranes show an enhanced permeation. Our combined experimental and computational results suggest that the transport mechanism is governed by the attraction of the solvents toward the pores with functional groups and hindered by the strong hydrogen network of water formed under angstrom confinement.

Chemical Vapour Deposition of Graphene for Durable Anticorrosive Coating on Copper.

Due to the excellent chemical inertness, graphene can be used as an anti-corrosive coating to protect metal surfaces. Here, we report the growth of graphene by using a chemical vapour deposition (CVD) process with ethanol as a carbon source. Surface and structural characterisations of CVD grown films suggest the formation of double-layer graphene. Electrochemical impedance spectroscopy has been used to study the anticorrosion behaviour of the CVD grown graphene layer. The observed corrosion rate of 8.08 × 10-14 m/s for graphene-coated copper is 24 times lower than the value for pure copper which shows the potential of graphene as the anticorrosive layer. Furthermore, we observed no significant changes in anticorrosive behaviour of the graphene coated copper samples stored in ambient environment for more than one year.