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（ZnO）纳米结构存在快速电子-空穴复合的问题，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（DNDs）等碳添加剂则受限于自身较高的缺陷密度。为解决上述问题，本研究合成了经高压高温纳米金刚石（HPHT NDs）改性的ZnO纳米复合材料，以探究其本征更低的缺陷密度——该特性可通过1330 cm⁻¹处的金刚石主拉曼峰，以及相较于带有强D/G拉曼带（~1350/1580 cm⁻¹）、sp²碳占比约25%~35%的氧化爆轰纳米金刚石更低的sp²碳占比（6.6%）得以验证——能否提升电荷分离效率并改善光催化活性。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ZnO实现共价结合，所得ND-ZnO复合材料通过扫描电子显微镜/能量色散X射线光谱（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（CL）进行了表征。能量色散X射线光谱结果证实，碳掺入量从13.0 at.%提升至52.9 at.%；X射线光电子能谱则显示，ND-ZnO 10样品的Zn 2p3/2峰发生了0.5 eV的位移，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，ND-ZnO 10的近带边发射得到增强，而间隙锌（Zni）相关发光（~3.0 eV）被抑制。ND-ZnO 10的降解速率常数（0.0251 min⁻¹）约为纯氧化锌（0.0087 min⁻¹）的3倍，且经过5次循环后仍保留88%的催化效率，展现出用于长效废水处理的巨大应用潜力。