ZnO/ZnFe2O4 nanocomposite/H2O2 shows NIR activity due to the absorption of NIR, electron–hole pair separation by p–n junction promoted charge transfer, and reaction of electrons with H2O2.

The development of full-spectrum photocatalysts active in the near-infrared (NIR) region has gained increasing attention in the photodegradation of organic pollutants. Herein, we designed a full-spectrum photocatalyst with strong NIR photoactivity based on the synergy of Er-doped ZnO-CuO-ZnAlO multi-phase oxides (Er-doped Zn/Cu/Al-MPO) via the formation of n-p-n double heterojunctions. The photocatalyst was prepared by synthesizing nanosheets of a Zn/Cu/Al/Er hydrotalcite-like compound (Zn/Cu/Al/Er-HLC) with a co-precipitation method followed by calcination of the nanosheets at 800 °C. The as-prepared Er-doped Zn/Cu/Al-MPO inherits the nanosheet morphology of Zn/Cu/Al/Er-HLC, and displays over-doubled photoactivity in the entire ultraviolet (UV), visible and NIR regions compared to undoped Zn/Cu/Al-MPO. The excellent photocatalytic activity of Er-doped Zn/Cu/Al-MPO, especially its strong NIR photoactivity, is ascribed to its Er-doped CuO-involved multi-crystalline phase heterostructure, i.e., n-p-n double heterojunctions, which does not only offer an enhanced NIR absorption but also promotes the separation of photogenerated charge carriers. Importantly, the synergy of all the parts of the n-p-n double heterojuctions plays an important role in interface band structure regulation for the enhancement of the photocatalytic properties of Er-doped Zn/Cu/Al-MPO. This work has demonstrated the feasibility of utilizing hydrotalcite-like precursors in the design of full-spectrum photocatalysts active in the NIR region.

Photocatalytic paper is a composite photocatalyst generally prepared by loading semiconductors, such as titanium dioxide (TiO 2) nanoparticles on paper, and attracts sustaining interests. In this paper, poly-dopamine (PDA) was loaded on cellulose fibre by in situ oxidative polymerization of dopamine. The PDA-loaded cellulose fibre (PLCF) was used to make TiO 2 photocatalytic paper together with pristine cellulose fibre (CF) and TiO 2 nanoparticles to improve the performance of the photocatalytic paper. The loading of PDA on CF and the introduction of TiO 2 nanoparticles in paper were verified by infrared spectroscopy and X-ray diffraction technique, respectively. As observed by scanning electron microscopy, the introduction of PLCF significantly improved the distribution of TiO 2 nanoparticles in paper by forming a membranous substance. The photocatalytic performance of the as-prepared photocatalytic paper was analysed by decomposing methyl orange under UV light irradiation. It was confirmed that the occurrence of PLCF significantly improved the photocatalytic performance of the photocatalytic paper. The paper with the highest photocatalytic activity was prepared using a PLCF-to-CF mass ratio of 1:1. The photocatalytic paper with PLCF is stable in the process of repeated application. This work provided a new approach to prepare photocatalytic paper with improved photocatalytic activity.

No abstract

Developing full-spectrum photocatalysts that harvests solar light from ultraviolet to near-infrared light has aroused great interest in photodegradation of organic pollutants, due to the imminent energy crisis and growing pollution issues. Herein, we report an excellent full-spectrum photocatalyst derived from calcination of an Mg/Zn/Al/Er-hydrotalcite-like compound. The photocatalyst is a stable multi-phase oxide consisting of various syntrophic Er3+-doped metal oxides with different particle sizes and morphology. Its ultraviolet (UV) photocatalytic activity is maximized by increasing the fraction of Zn2+ and sustaining the pure hydrotalcite-like phase with an appropriate fraction of Mg2+ in preparing the Mg/Zn/Al/Er-hydrotalcite-like precursor. The visible and NIR photocatalytic activities are triggered by an indirect excitation involving an up-conversion process. The major active species of the photocatalyst in the photodegradation of methyl orange are superoxide anions and photogenerated holes. Nevertheless, hydroxyl radicals also play a moderate role in the photodegradation process. This work finds a new way to prepare full-spectrum photocatalysts with tunable chemical compositions via an environmentally friendly hydrotalcite-like precursor.