Photocatalytic synthesized low content CeO2-modified rutile heterojunction photocatalysts with enhanced wastewater treatment and H2 evolution performances

Abstract

High performance composite photocatalyst is a hotspot in the photocatalysis researches. In this study, a cutting-edge CeO2/rutile composite photocatalyst with tiny CeO2 concentration of 1.28 wt% was synthesized via a simple photocatalytic method. This as-obtained CeO2/rutile catalyst (CeO2/TiO2-1:1) exhibited an enhanced wastewater degradation and improved water splitting H2 evolution ability, with 95.83 % removal ratio for methylene blue (MB), 72.84% for tetracycline (TC) and 87.57 μmol/g H2 evolution capacity. Light irradiation and 2-coordinated oxygen vacancies (OV2C) on rutile surface promoted the Ce3+ adsorption on the rutile (110) facet as DFT results shown. The CeO2/rutile type-II heterojunction was evidenced to promote the migration of e−/h+ and generation of ·OH/·O2− and H2, which rapidly boosted the whole photocatalytic performance. This as-prepared CeO2/TiO2 photocatalyst can provide useful inspirations and new thoughts about the photosynthesis process, and offer a novel strategy for heterojunction photocatalysts preparation.

1. Introduction

In the rapidly evolving economic and social development, the growing severity of wastewater pollution, particularly from organic dye and antibiotic contaminants, has attracted global attention and significant research efforts [1−3]. Moreover, the microplastic becomes another noteworthy pollutant [4−6]. Differ to the common treatments such as electrocoagulation [7−9], photocatalysis emerges as the most eco-friendly solution, aligning with the sustainable industrial development goals [10−14]. Meanwhile, the environmental pollution bedeviling with traditional fossil fuel burning drives to the great command for new clean energy sources [15], and hydrogen (H2) is the most anticipated one for its high heating value, carbon-free and pollution-free [16, 17], while photocatalysis method is also capable to be an effective, efficient and environment-friendly method for H2 production [18−20].

The photocatalyst plays a pivotal role in photocatalysis reaction, however, finding highly efficient photocatalysts remains a critical challenge to the researchers [21]. Ceria (CeO2), a rare earth oxide, is renowned for its photocatalytic process due to its high oxygen storage capacity, robust chemical and thermal stability, and superior redox characteristics [22]. However, due to the wide band gap (2.7−3.4 eV) and quick recombination rate of photo-generated electrons (e−) and holes (h+), further photocatalytic applications of CeO2 are restricted [23]. Rutile is also a commonly used photocatalyst [24−27], but the low production of photo-excited carriers constrains its development applications in photocatalysis [28]. Designing and fabricating CeO2/rutile complex photocatalysts is an available method to offset respective shortcomings and enhance comprehensive photocatalytic properties, which is expectable to improve the performance shortcomings of both parties [29, 30] mainly via the optimization of photochemical activity [31, 32].

For CeO2-based composite catalysts, low CeO2 loading catalysts are the research hotspot and focus in the CeO2 catalysts field [33]. Low CeO2 loading has a number of advantages such as even dispersion of active centers, high utilization ratio of active sites, stable and high performance, and low waste of load components [34, 35]. The low CeO2 loading photocatalysts also stimulate much research enthusiasm in the related field with their satisfied photochemical performances [36, 37], nevertheless, the specific enhancement mechanism of the low content loaded CeO2 is still inconclusive.