Tang Tian, Ren Penghui, Xue Jingyu, Chen Jinfei, Qiao Wenyun, Zhang Heyuan, Li Shanhong, Li Xinbao, Du Xuesen
Key Laboratory of Low-Grade Energy Utilization Technologies and Systems, Ministry of Education of PRC, Chongqing University, Chongqing 400044, China; School of Energy and Power Engineering, Chongqing University, Chongqing 400044, China.
Beijing Key Lab for Source Control Technology of Water Pollution, College of Environmental Science and Engineering, Beijing Forestry University, Beijing 100083, China.
J Hazard Mater. 2025 Sep 15;496:139363. doi: 10.1016/j.jhazmat.2025.139363. Epub 2025 Jul 29.
The heterogeneity (acid sites) and stability (redox sites) of metal loss on metal-acid catalyst surfaces are the fundamental factors for the "trade-off" effect between activity and selectivity in the catalytic process with NH as the activation precursor. However, the molecular-level impact of these surface characteristics on catalytic performance remains unclear and contentious. Herein, we propose a straightforward decomposition temperature control method, which operates below the single-layer dispersion threshold of solid sulfate/nitrate precursors. This method adjusts the micro-coordination electronic environment and work function of the active site by employing (2 H)SO species with negligible structural influence, thereby achieving precise control over the redox properties and acidity of metal-acid catalysts. In the NH oxidation model reaction, ab initio molecular dynamics (AIMD) simulations show that even at 500 K, the (2 H)SO species can direct the dissociation of nearby adsorbed NH into -NH species. This is due to the (2 H)SO species can strip the electrons from the antibonding states below the Fermi level of the -NH species via the high-position chemisorbed oxygen 2p orbitals, thereby reducing the electron state energy of the -NH species through the -NH-1s-2p-(2 H)SO bond, even these Brønsted strong acid sites does not participate in the low-temperature NH oxidation. This prevents the over-oxidation of -NH species, anchoring the nearby high-selectivity i-SCR intermediate. Diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) results confirm that abundant -NH species at high temperatures can overcome the spatial steric hindrance of (2 H)SO species, enhancing the N selectivity via the i-SCR mechanism (-NH + NO/Nitrate → N + HO).
金属-酸催化剂表面金属损失的不均匀性（酸性位点）和稳定性（氧化还原位点）是在以NH为活化前驱体的催化过程中活性与选择性之间“权衡”效应的基本因素。然而，这些表面特性对催化性能的分子水平影响仍不明确且存在争议。在此，我们提出一种直接的分解温度控制方法，该方法在固体硫酸盐/硝酸盐前驱体的单层分散阈值以下操作。此方法通过使用对结构影响可忽略不计的(2 H)SO物种来调整活性位点的微配位电子环境和功函数，从而实现对金属-酸催化剂的氧化还原性质和酸度的精确控制。在NH氧化模型反应中，从头算分子动力学（AIMD）模拟表明，即使在500 K时，(2 H)SO物种也能将附近吸附的NH解离为-NH物种。这是因为(2 H)SO物种可通过高位置化学吸附氧2p轨道从-NH物种费米能级以下的反键态夺取电子，从而通过-NH-1s-2p-(2 H)SO键降低-NH物种的电子态能量，即使这些布朗斯特强酸位点不参与低温NH氧化。这可防止-NH物种过度氧化，锚定附近的高选择性i-SCR中间体。漫反射红外傅里叶变换光谱（DRIFTS）结果证实，高温下大量的-NH物种可克服(2 H)SO物种的空间位阻，通过i-SCR机制（-NH + NO/硝酸盐→N + HO）提高N选择性。
