Synergy of S-vacancy and heterostructure in BiOCl/Bi2S3-x boosting room-temperature NO2 sensing.

The special physicochemical properties of Bi2S3 nanomaterial endow it to be exceptional NO2 sensing properties. However, sensors based on pure Bi2S3 cannot detect trace NO2 at room temperature effectively due to the scanty active sites and poor charge transfer efficiency. Herein, vacancy defect and heterostructure engineering are rationally integrated to explore BiOCl/Bi2S3-x heterostructure with rich S vacancies to enhance NO2 sensing performance. The optimized sensor based on S-vacancy-rich BiOCl/Bi2S3-x heterostructure exhibited a high response value (Rg/Ra = 29.1) to 1 ppm NO2 at room temperature, which was about 17 times compared to the pristine Bi2S3. Meanwhile, the BiOCl/Bi2S3-x sensor also exhibited a short response time (36 s) towards 1 ppm NO2 and a low theoretical detection limit (2 ppb). The superior response value of S-vacancy-rich BiOCl/Bi2S3-x heterostructures was ascribed to the improved electron migration at the heterointerface and the additional exposed active sites caused by the S vacancies in Bi2S3-x. Additionally, the sensors based on S-vacancy-rich BiOCl/Bi2S3-x heterostructures showed good long-term stability, outstanding selectivity, and good flexibility. This study offers an effective method for synergistically engineering defect and heterostructure to enhance gas sensing properties at room temperature.

Corrosion Behavior of High-Cr-Ni Materials in Biomass Incineration Atmospheres.

In this paper, the corrosion test of high-Cr-Ni tubes was carried out in a biomass incinerator by replacing the original heated surface tube with a test tube. The investigated materials are high-Cr-Ni stainless steels (TP347H, SP2215, and Sanicro25) and alloy (HT700T). Long-term services (>4000 h) to investigate the corrosion rates and corrosion characteristics of the materials have been carried out. The appearance, element content, and composition of corrosion products after corrosion of the specimens were analyzed. Analysis indicates that the deposits are mainly composed of alkali metal salts, iron oxides, iron sulfates, and complex salts. Moreover, the corrosion morphology of the materials with different Cr-Ni contents varies greatly. TP347H has a high corrosion rate (0.11 mm/1000 h) with intergranular corrosion cracks and pitting on the windward side. However, the corrosion pattern of HT700T is comprehensive corrosion and the corrosion rate is low (0.015 mm/1000 h). Using corrosion rate as a criterion for corrosion resistance, HT700T has the highest corrosion resistance, while TP347H has the lowest. The corrosion behavior is also related to the corrosion resistance index (CI) value based on the content of critical elements. The order of material corrosion resistance predicted by the CI value is the same as reflected by the corrosion rate.