Enhanced triboelectric nanogenerators based on 2D smectite clay nanosheets with a strong intrinsic negative surface charge

Triboelectric nanogenerators (TENGs) have demonstrated their huge potential in micro/nano energy harvesting for self-powered systems. The output performance of TENGs is largely dependent on the surface charge density of the triboelectric materials. Here, for the first time, we propose 2D smectite clay (SC) nanosheets with a strong intrinsic negative surface charge for improving the charge density of traditional triboelectric-negative materials. A single-layer 2D SC nanosheet (∼1.1 nm thick) showed a strong negative surface potential (−14.3 mV), and the SC was confirmed to have a strong triboelectric negativity close to that of polytetrafluoroethylene (PTFE). 2D SC nanosheets were blended into polyvinylidene fluoride (SC-PVDF), based on which the SC-TENG demonstrated a significantly enhanced output performance, with the transferred charge increasing from 14 nC to 35 nC at the optimal SC concentration of 5 wt%. At higher SC concentrations, the influence of decreased effective contact area because of severe aggregation of SC nanosheets began to outperform the effect of increased interior charge. The instantaneous output power density of the SC-TENG was enormously improved to 1450 mW/m2 from that of the pristine TENG (15 mW/m2). This work proposed a new 2D material, SC, with a strong intrinsic negative surface charge, which has huge prospects in enhancing the output performance of TENGs.