Based on the density functional theory (DFT), we investigate the friction properties of inevitable oxidized black phosphorus (o-BP). o-BP with the weaker interlayer adhesion exhibits their great potential as a solid lubricant. At the zero load, the friction property of o-BP is adjusted by its oxidation degree. Expressly, ultra-low friction of P4O2 (50% oxidation, O : P = 2 : 4 = 50%) is obtained, which is attributed to the upper O atoms with lower sliding resistance in the O channel formed by lower layer O atoms. More attractive, we observe superlubricity behavior of o-BP at the critical load/distance due to the flattening potential energy surface (PES). The flattening PES is controlled by the electrostatic role for the high-load (P4O3, O : P = 3 : 4 = 75%), and by the electrostatic and dispersion roles for the low-load (P4O2). Distinctly, the transform from ultra-low friction to superlubricity state of black phosphorus (BP) can be achieved by critical oxidation and load, which shows an important significance in engineering application. In addition, negative friction behavior of o-BP is a general phenomenon (Z > Z_min, Z_min is the interlayer distances between the outermost P atoms of minimum load.), while its surface-surface model is different from the fold mechanism of the tip-surface model (Z₀ < Z < Z_min, Z₀ is the interlayer distances between the outermost P atoms of equilibrium state.). Thus, this phenomenon cannot be captured due to the jump effect with instability of the atomic force microscopy (AFM) (Z > Z_min). In summary, o-BP improves the friction performance and reduces the application limitation, comparing to graphene (Gr), MoS₂, and their oxides.

基于密度泛函理论（DFT），我们研究了不可避免的氧化黑磷（o-BP）的摩擦特性。o-BP具有较弱的层间附着力，显示出其作为固体润滑剂的巨大潜力。在零负载时，o-BP的摩擦性能通过其氧化程度来调节。具体来说，P4O2 获得了超低摩擦（50%氧化，O:P=2:4=50%），这归因于上层 O 原子在下层 O 原子形成的 O 通道中具有较低的滑动阻力。更有吸引力的是，我们观察到由于势能面（PES）平坦，o-BP 在临界负载/距离下的超润滑行为。对于高负载 (P4O3, O : P = 3 : 4 = 75%)，平坦化 PES 由静电作用控制，对于低负载 (P4O2)，则由静电和色散作用控制。明显地，通过临界氧化和加载可以实现黑磷(BP)从超低摩擦态向超润滑态的转变，在工程应用中具有重要意义。此外，o-BP的负摩擦行为是一种普遍现象（Z > Z_min , Z _min是最小载荷最外层P原子之间的层间距离。），而其表面-表面模型与尖端-表面模型的折叠机制不同（Z 0 < Z < _Z min _， Z ₀是平衡态最外层 P 原子之间的层间距离。）。_{因此，由于原子力显微镜（AFM）（Z > Z min}）不稳定的跳跃效应，无法捕获这种现象。总之，与石墨烯（Gr）、MoS ₂及其氧化物相比，o-BP提高了摩擦性能并减少了应用限制。