Ba-mediated Pt/TiO<sub>2</sub> for Enhanced Low Temperature HCHO Oxidation: the Role of Pt Precursor

Article Ba-mediated Pt/TiO2 for Enhanced Low Temperature HCHO Oxidation Originated from the Interaction between Pt and Ba Chenxuanzhi Ruan 1,2, Hongguo Gao 1, Xuejuan Zhao 2, Zelin Hua 1, Shenjie Lv 1, Shanshan Chen 3,*, and Licheng Li 1,* 1 Jiangsu Co-Innovation Center of Efficient Processing and Utilization of Forest Resources, College of Chemical Engineering, Nanjing Forestry University, Nanjing 210037, China 2 School of Materials Science and Engineering, Nanjing Institute of Technology, Nanjing 211167, China 3 School of Materials Science and Engineering, Nankai University, Tianjin 300350, China * Correspondence: [email protected] (S.C.); [email protected] (L.L.) Received: 22 January 2025; Revised: 27 February 2025; Accepted: 10 March 2025; Published: 11 March 2025 Abstract: The alkaline earth metals have recently been reported to exhibit a similar role as alkali metals in enhancing the low temperature formaldehyde (HCHO) oxidation performance of precious metal supported catalysts; however, its essential mechanism is still not well understood. In this work, it is found that the Pt precursor is critical for Ba-mediated Pt/TiO2 catalyst to achieve the efficient HCHO oxidation performance. Catalytic results indicate that Pt/TiO2 catalysts using tetraammineplatinum(II) nitrate (Pt(NH3)4(NO3)2) and chloroplatinic acid (H2PtCl6) as Pt precursors exhibit comparable performance in HCHO oxidation. Notably, the Ba-mediated Pt/TiO2 catalyst synthesized from Pt(NH3)4(NO3)2 shows exceptional catalytic performance, with its HCHO reaction rate being 3.8-fold that of Pt/TiO2, while the Ba-mediated Pt/TiO2 catalyst derived from H2PtCl6 has the similar catalytic activity to that of Pt/TiO2. Series characterization results reveal that the Ba species can strongly interact with Pt to form the Ba-O-Pt active site within the Ba-mediated Pt/TiO2 catalyst derived from Pt(NH3)4(NO3). However, such interaction is not observed in the catalyst synthesized from H2PtCl6. Additionally, more oxygen species and hydroxyl groups can be adsorbed and activated on the Ba-O-Pt active site than those on the typical Pt active site, and HCHO undergoes efficient oxidation on the Ba-O-Pt active site via a different reaction pathway (HCHO→HCOO− + OH→H2O + CO2) analogous to that observed on alkali metal-mediated active site. These findings can provide a deep insight into the development of highly efficient catalysts for low temperature HCHO oxidation.