In this study, mechanical vibration is used for hydrogen generation and decomposition of dye molecules, with the help of BiFeO3 (BFO) square nanosheets. A high hydrogen production rate of ≈124.1 μmol g−1 is achieved under mechanical vibration (100 W) for 1 h at the resonant frequency of the BFO nanosheets. The decomposition ratio of Rhodamine B dye reaches up to ≈94.1 % after mechanical vibration of the BFO catalyst for 50 min. The vibration‐induced catalysis of the BFO square nanosheets may be attributed to the piezocatalytic properties of BFO and the high specific surface area of the nanosheets. The uncompensated piezoelectric charges on the surfaces of BFO nanosheets induced by mechanical vibration result in a built‐in electric field across the nanosheets. Unlike a photocatalyst for water splitting, which requires a proper band edge position for hydrogen evolution, such a requirement is not needed in piezocatalytic water splitting, where the band tilting under the induced piezoelectric field will make the conduction band of BFO more negative than the H2/H2O redox potential (0 V) for hydrogen generation.

A strong pyro-catalytic dye degradation with an ultrahigh degradation efficiency (>99%) in hydrothermally synthesized pyroelectric BiFeO3 nanoparticles was achieved under a room-temperature cold-hot alternating excitation (between 27 °C to 38 °C). The pyro-catalysis originated from a combination of the pyroelectric effect and the electrochemical oxidation-reduction reaction. The intermediate products (hydroxyl radicals and superoxide radicals) of pyro-electro-catalysis were observed. Pyro-catalysis provides a highly efficient and reusable dye wastewater decomposition technology through utilizing environmental day-night temperature variation.

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Many 2D few-layer materials show piezoelectric or pyroelectric effects due to the loss-of-inversion symmetry induced by broken structure, although they are not piezoelectric or pyroelectric in the bulk. In this work, we find that the puckered graphene-like 2D few-layer black phosphorene is pyroelectric and shows a pyro-catalytic effect, where the pyroelectric charges generated under ambient cold–hot alternation are utilized for hydrogen evolution and dye molecule decomposition. Under thermal cycling between 15 °C and 65 °C, the 2D few-layer black phosphorene shows a direct hydrogen generation of about 540 μmol per gram of catalyst after 24 thermal cycles and about 99% decomposition of Rhodamine B dye after 5 thermal cycles. This work opens a door for the pyro-catalytic energy harvesting from the cold–hot alternations by a class of 2D few-layer materials.

Supportinginformation and the ORCID identification number(s) for the author(s) of this article can be found under: https://doi.

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Ultrathin transition metal dichalcogenides (TMDs) are of particular interest as low-cost alternatives to highly active electrocatalysts because of their high surface activation energy. However, their striking structural characteristics cause chemical instability and undergo oxidation easily. Establishing a transparent material model for unraveling oxidation-dependent electrocatalysis is of great importance for designing more efficient electrocatalysts. Herein, we fabricated an on-chip microcell that uses an individual nanosheet as the working electrode to evaluate the contribution of a single oxidation factor to hydrogen evolution reaction (HER) performance in the generation of oxidative molybdenum ditelluride (MoTe 2 ) for the fabrication of the on-chip electrocatalytic device. Moreover, O 2 plasma technology was utilized to control the degree of oxidation accurately by the processing time. Using oxidized MoTe 2 as a prototype demonstrated lower onset overpotential and activation energy of HER performance, which was optimized to some degree by oxidation. The incorporated oxygen during the oxidation process as an electron density modulator could manipulate the electron densities and contribute to the enriched surface charge and lower Gibbs reaction energy. Our present work provides atomic-level insights into the role of surface oxide in ultrathin TMDs HER catalysis by an on-chip electrocatalytic microdevice and the semiquantification of the model-structureperformance relationship, thus, opening the door for designing catalytic centers.

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