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ORIGINAL PAPER

Formaldehyde Oxidation on Pd/TiO2 Catalysts at Room Temperature: The Effects of Surface Oxygen Vacancies Yaobin Li1,2 · Chunying Wang2,4 · Changbin Zhang3,4 · Hong He1,2,3,4

© Springer Science+Business Media, LLC, part of Springer Nature 2020

Abstract High reduction temperature generally induces the agglomeration of supported noble metals. Howerve, we found that high temperature reduction did not induce Pd particles sintering but improved Pd dispersion. Multiple methods were further carried out to illuminate the abnormal phenomenon. The results indicated more surface oxygen defects and diffusion of Pd particles were simultaneously induced by high temperature reduction. During diffusion process of Pd particles, they were trapped by the oxygen defects because of the strong metal-support interaction, which led to improvement of Pd dispersion on the Pd/TiO2-450R catalyst. In addition, more surface oxygen vacancies on the Pd/TiO2-450R catalyst resulted in more active sites of H ­ 2O activation to form abundant surface OH groups which further enhanced adsorbed O ­ 2 activation and mobility, and then opening a more effective pathway for HCHO oxidation, which result in its high activity of Pd/TiO2-450R for ambient HCHO oxidation. Keywords  Oxygen vacancies · Dispersion · High temperature reduction · Formaldehyde · Catalytic oxidation

1 Introduction Formaldehyde (HCHO), emitting from building/furnishing materials and decorative products, is one of the main indoor pollutants [1]. It is well known that HCHO is harmful to human health, leading to nasal tumors, headache, eye irritation, respiratory tract or even cancer [2]. With increasing attention paid on the pollution of HCHO, effective methods to remove indoor HCHO is of great importance for improving indoor air quality and reducing public health risks. * Hong He [email protected] 1



Ningbo Urban Environment Observation and Research Station, Institute of Urban Environment, Chinese Academy of Sciences, Ningbo 315800, China

2



Center for Excellence in Regional Atmospheric Environment, Key Laboratory of Urban Pollutant Conversion, Institute of Urban Environment, Chinese Academy of Sciences, Xiamen 361021, China

3

State Key Joint Laboratory of Environment Simulation and Pollution Control, Research Center for Eco‑Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China

4

University of Chinese Academy of Sciences, Beijing 100049, China





Several methods, such as adsorption [3], photo-catalysis [4] and catalytic oxidation [5] have been used to remove HCHO. In comparison, catalytic oxidation is widely recognized to be the promising method because HCHO oxidation could be effectively decomposed into harmless ­CO2 and ­H2O without any secondary pollution [6]. For decades, metal oxide catalysts (Ag, Mn, Co and Ni) [7–16] and supported noble metal (Pt, Au, Pd, Ir, Rh) catalysts [17–21] were attracting attention of researchers for HCHO oxidation. The former usually needed higher reaction temperature to completely decompose HCHO, while