In this paper, we design a self-powering dual mode simultaneous wireless information and power transfer (SWIPT) system in which a sensor node adaptively controls single tone or multi-tone communication mode. To this end, we introduce duty cycle operation for the dual mode SWIPT with self-powering, which considers nonlinear energy harvesting (EH) model for both single tone and multi-tone waveforms. We formulate an adaptive mode switching (MS) problem which maximizes the achievable rate under the energy causality condition. On top of this, a novel iterative inner/outer loop algorithm is implemented to solve the adaptive MS problem. Our newly designed dual mode SWIPT can be applied to low-power Internet-of-Things (IoT) network with wireless EH capability for self-powering, thereby realising battery-free IoT network. From the results presented, we provide interesting insights that can be applied to design the dual mode SWIPT system over existing SWIPT.