Abstract It has been widely documented that the oxygen-containing functionalities, especially carboxyl groups, on carbon surfaces play crucial roles in the catalytic wet air oxidation (CWAO) reactions. Herein, the CWAO of phenol with molecular O2 as terminal oxidant using cylindrical and herringbone carbon nanotubes (CNTs) underwent different treatments as catalysts were conducted in batch mode. It was uncovered that the catalytic function of carboxyl groups strongly depended on the structure of CNTs. Parallel CNTs (p-CNTs) with cylindrical graphitic walls displayed the highest catalytic activity after nitric acid oxidation, due to the carboxylated carbon debris (CDs) coating on surfaces. For herringbone CNTs (h-CNTs), carboxyl groups are mostly linked to its sidewalls, where abundant edge carbons were exposed, providing an enhanced CWAO activity. The positively synergistic effect of carboxyl groups and adjacent edge carbons was responsible for the activation of O2, leading to the improved CWAO activity. This study provides a new insight into the structural effect of carbon materials on the CWAO of phenol.

中文翻译：

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苯酚在碳纳米管上的催化湿空气氧化：羧基和边缘碳的协同作用

摘要 碳表面的含氧官能团，尤其是羧基，在催化湿空气氧化 (CWAO) 反应中起着至关重要的作用，这已被广泛证明。在此，使用圆柱形和人字形碳纳米管 (CNT) 作为催化剂以间歇模式进行的苯酚 CWAO 与分子 O2 作为末端氧化剂进行了不同的处理。发现羧基的催化功能强烈依赖于碳纳米管的结构。由于表面的羧化碳碎片 (CD) 涂层，具有圆柱形石墨壁的平行碳纳米管 (p-CNT) 在硝酸氧化后显示出最高的催化活性。对于人字形碳纳米管（h-CNTs），羧基主要连接到其侧壁，在那里大量的边缘碳暴露，提供了增强的 CWAO 活性。羧基和相邻边缘碳的正协同作用是 O2 活化的原因，导致 CWAO 活性提高。该研究为碳材料对苯酚 CWAO 的结构影响提供了新的见解。