Developing high-performance visible-light driven photocatalyst (λ ≥ 420 nm) makes significance for the efficient utilization of solar energy. Mass production and easy recycling are equally important for the practical application of powdery photocatalyst. However, it is challenging to meet the above requirements at the same time. In this work, we develop an efficient visible-light responsive layered oxyiodide CdBiO₂I nanosheets prepared by a facile direct precipitation method at ambient atmosphere, and demonstrate its upgradable features well fitting potential application. CdBiO₂I has a layered crystal structure consisting of [CdBiO₂]⁺ layer and I⁻ single layer, differing from that of BiOI composed of [BiO₂]²⁺ layer and I⁻ double layers. It displays an absorption edge of 520 nm in visible region, with a band gap of 2.52 eV CdBiO₂I has a large intrinsic effective mass difference of hole/electron, exceeding BiOI by 8-fold, which results in much higher charge separation efficiency and production of more reactive species (superoxide radicals and holes). The degradation efficiency of CdBiO₂I nanosheets for tetracycline hydrochloride reaches 84% under the visible light irradiation within 1 h, in which the degradation rate is 10 times that of BiOI. In addition, mass production (12 g catalyst at one time) and immobilization onto porous polyurethane foam of CdBiO₂I powder are also demonstrated, which indicates the scalable properties and easy recovery of the catalyst, highlighting the advantages of the current preparation method and prefiguring its potential in practical applications. This work may enlighten future research on the exploitation of solar-driven catalyst with high efficiency and strong practical applicability.

Piezoelectric semiconductors bear the bifunctional photocatalysis and piezocatalysis, while the absent or weak internal charge driving force severely restricts its catalytic activity. Developing polarization strategy is desirable, and particularly understanding its mechanism from a microscopic perspective remains scanty. Herein, we report a secondary recrystallization approach to achieving the simultaneous micro- and macroscopic polarization enhancement on Bi₂WO₆ nanosheets for boosting piezo-photocatalytic oxygen activation, and unravel the mechanism at an atom-level. The secondary recrystallization process not only results in a strengthened distortion of [WO₆] octahedra with distortion index enhancement by ～ 20% for a single octahedron, but also enables lateral crystal growth of nanosheets along the ab plane (av. 50 to 180 nm), which separately allows the rise in dipole moment of unit cell (e.g., 1.63 D increase along a axis) and the stacking of the distorted [WO₆] octahedron to accumulate the unit cell dipole, collectively contributing to the considerably strengthened spontaneous polarization and piezoelectricity. Besides, exposure of large-area {001} front facet enables more efficient capture and conversion of stress into piezo-potential. Therefore, the well-recrystallized Bi₂WO₆ nanosheets exhibit considerably promoted piezo-photocatalytic reactive oxygen species generation, given the decreased specific surface area. This work presents a feasible methodology to regulate inside-out polarization for guiding carriers transfer behavior, and may advance the solid understanding on the intrinsic mechanism.

For decades, global warming and energy shortages have been two urgent problems in human society. The solar-driven photocatalytic conversion of carbon dioxide (CO₂) into hydrocarbon fuels is expected to become a technology to solve these problems. Two-dimensional (2D) materials shine in the field of photocatalytic CO₂ due to their layered structure, larger specific surface area, more active sites, and larger charge transfer efficiency. This article reviews the progress of CO₂ reduction by several types of 2D materials in recent years. Generally, the reduction of CO₂ is difficult in terms of kinetics and thermodynamics, but it is found through theoretical calculations and experiments that 2D materials have certain advantages in the reduction of CO₂. Then the preparation methods of 2D materials are summarized and a variety of 2D materials are discussed and classified. Finally, an outlook on the development trend of 2D materials is made. This review aims to provide systematic and concise guidance for the design of 2D nanomaterials for photocatalytic CO₂ reduction.