School of Environmental and Municipal Engineering, Xi'an University of Architecture and Technology, Xi'an 710055, China; Key Laboratory of Northwest Water Resources, Environment and Ecology, Ministry of Education, Xian 710055, China; State Key Laboratory of Urban Water Resource and Environment, Harbin Institute of Technology, Harbin 150090, China.
School of Environmental and Municipal Engineering, Xi'an University of Architecture and Technology, Xi'an 710055, China.
J Environ Sci (China). 2025 Mar;149:221-233. doi: 10.1016/j.jes.2024.01.011. Epub 2024 Jan 24.
Catalytic reduction of nitrate over bimetallic catalysts has emerged as a technology for sustainable treatment of nitrate-containing groundwater. However, the structure of bimetallic has been much less investigated for catalyst optimization. Herein, two main types of Pd-Cu bimetallic nanocrystal structures, heterostructure and intermetallic, were prepared and characterized using high-resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). The results show that two individual Pd and Cu nanocrystals with a mixed interface exist in the heterostructure nanocrystals, while Pd and Cu atoms are uniformly distributed across the intermetallic Pd-Cu nanocrystals. The catalytic nitrate reduction experiments were carried out in a semibatch reactor under constant hydrogen flow. The nitrate conversion rate of the heterostructure Pd-Cu nanocrystals supported on α-AlO, γ-AlO, SBA-15, and XC-72R exhibited 3.82-, 6.76-, 4.28-, 2.44-fold enhancements relative to the intermetallic nanocrystals, and the nitrogen and nitrite were the main products for the heterostructure and intermetallic Pd-Cu nanocrystals, respectively. This indicates that the catalytic nitrate reduction over Pd-Cu catalyst is sensitive to the bimetallic structures of the catalysts, and heterostructure bimetallic nanocrystals exhibit better catalytic performances on both the activity and selectivity, which may provide new insights into the design and optimization of catalysts to improve catalytic activity and selectivity for nitrate reduction in water.
双金属催化剂上的硝酸盐催化还原已成为一种可持续处理含硝酸盐地下水的技术。然而，对于催化剂优化，双金属的结构研究要少得多。本文采用高分辨率透射电子显微镜（HRTEM）、X 射线衍射（XRD）和 X 射线光电子能谱（XPS）等方法制备和表征了两种主要类型的 Pd-Cu 双金属纳米晶结构，即异质结构和金属间化合物。结果表明，在异质结构纳米晶中存在两个具有混合界面的单独 Pd 和 Cu 纳米晶，而在金属间化合物 Pd-Cu 纳米晶中 Pd 和 Cu 原子均匀分布。在恒氢流下的半分批式反应器中进行了催化硝酸盐还原实验。在α-AlO、γ-AlO、SBA-15 和 XC-72R 上负载的异质结构 Pd-Cu 纳米晶的硝酸盐转化率分别比金属间化合物纳米晶提高了 3.82、6.76、4.28 和 2.44 倍，而异质结构和金属间化合物 Pd-Cu 纳米晶的主要产物是氮气和亚硝酸盐。这表明，Pd-Cu 催化剂上的催化硝酸盐还原对催化剂的双金属结构敏感，异质结构双金属纳米晶在活性和选择性方面表现出更好的催化性能，这可能为设计和优化催化剂以提高水中硝酸盐还原的催化活性和选择性提供新的思路。
