This paper investigates a wireless-powered secure communication system enhanced by a multi-layer intelligent reflecting surface (IRS) operating within the terahertz frequency band. In this framework, an access point (AP) transmits confidential information to a legitimate user, while a passive eavesdropper attempts to intercept the confidential signal. To extend the operational lifespan of the legitimate user, a power splitting (PS)-based energy harvesting (EH) strategy is employed. The primary aim is to maximize the achievable secrecy rate through the joint design of the transmit beamformer, the IRS reflecting matrix, the baseband digital processing matrix, and the PS ratio. To address this complex non-convex optimization problem, we propose an alternate optimization (AO) algorithm that utilizes Taylor series expansions in conjunction with semidefinite relaxation (SDR) techniques. Simulation results reveal that the proposed multi-layer IRS-assisted secure communication framework significantly enhances the secrecy rate in terahertz systems while simultaneously facilitating effective information and power transmission.