High-Pressure High-Temperature Nanodiamond-Modified ZnO Nanocomposites as Promising Photocatalysts: Synthesis and Characterization

Zinc oxide (ZnO) nanostructures suffer from fast electron–hole recombination, limiting their applicability in photocatalytic environmental remediation, and carbon additives such as detonation nanodiamonds (DNDs) are constrained by their high defect density. To address this, ZnO nanocomposites modified with high-pressure, high-temperature nanodiamonds (HPHT NDs) were synthesized to evaluate whether their intrinsically lower defect density—evidenced by a dominant diamond Raman peak at 1330 cm−1 and a low sp2 carbon fraction of 6.6% compared to oxidized DNDs with strong D/G bands (~1350/1580 cm−1) and ~25–35% sp2 carbon—can enhance charge separation and improve photocatalytic activity. Oxidized HPHT NDs bearing carbonyl, carboxyl, and hydroxyl groups enabled covalent attachment to ZnO, and the resulting ND–ZnO composites were characterized by SEM/EDX, ATR-FTIR, Raman spectroscopy, XPS, and cathodoluminescence (CL). EDX confirmed increasing carbon incorporation from 13.0 to 52.9 at.%, while XPS revealed a 0.5 eV shift in the Zn 2p3/2 peak and an increase in Zn–O–Zn lattice oxygen from 31.3% to 61.6% in ND–ZnO 10. CL showed enhanced near-band-edge emission and reduced Zni-related luminescence (~3.0 eV). ND–ZnO 10 achieved a nearly threefold-higher degradation rate constant (0.0251 min−1) than pristine ZnO (0.0087 min−1) and retained 88% efficiency after five cycles, demonstrating strong potential for durable wastewater treatment.氧化锌（Zinc oxide, ZnO）纳米结构存在电子-空穴复合过快的问题，限制了其在光催化环境修复领域的应用；而爆轰纳米金刚石（detonation nanodiamonds, DNDs）这类碳添加剂则受限于自身较高的缺陷密度。为解决这一难题，我们合成了经高压高温纳米金刚石（high-pressure, high-temperature nanodiamonds, HPHT NDs）改性的氧化锌纳米复合材料，以评估其本征更低的缺陷密度能否增强电荷分离效率并提升光催化活性——该低缺陷密度特性可通过两项特征得以证实：一是在1330 cm⁻¹处出现显著的金刚石拉曼主峰，二是相较于带有强D/G峰（~1350/1580 cm⁻¹）且sp²碳占比约25%~35%的氧化爆轰纳米金刚石，该材料的sp²碳占比仅为6.6%。带有羰基、羧基与羟基官能团的氧化型高压高温纳米金刚石可与氧化锌实现共价结合，所得的ND-ZnO复合材料经扫描电子显微镜/能谱仪（SEM/EDX）、衰减全反射傅里叶变换红外光谱（ATR-FTIR）、拉曼光谱、X射线光电子能谱（XPS）以及阴极发光（cathodoluminescence, CL）表征。能谱分析证实复合材料的碳掺入量从13.0 at.%提升至52.9 at.%；X射线光电子能谱结果显示，ND-ZnO 10样品的Zn 2p3/2峰发生了0.5 eV的偏移，且Zn-O-Zn晶格氧占比从31.3%提升至61.6%。阴极发光测试表明，样品的近带边发射得到增强，而与Zni相关的发光（~3.0 eV）则显著减弱。ND-ZnO 10的降解速率常数（0.0251 min⁻¹）近乎是纯氧化锌（0.0087 min⁻¹）的三倍，且经过五次循环催化后仍保留88%的催化效率，展现出用于长效污水处理的极佳应用潜力。