Internet of Things (IoT) promotes a heightened level of awareness about our world and makes our life more intelligent and convenient. In IoT, machine-to-machine (M2M) communications enables direct connectivities among machines and devices to automatically exchange information and perform actions. Low Power Wide Area (LPWA) plays a crucial role in provisioning wide area coverage and low energy consumption network for M2M communications in IoT. Moreover, green energy harvesting is essential for mobile machine type-devices (MTDs) to achieve their self-sustainability and independence. Therefore, we propose dual-battery architecture to empower MTDs with concurrent green energy harvesting and IoT functionalities. Rather than routing through an LPWA base station (BS), direct and dual-hop transmissions are proposed for proximal M2M communications. According to the residual green energy in the MTDs' batteries, we provision a relay incentive policy and relay selection schemes to facilitate direct and dual-hop M2M communications. For dual-hop M2M communications, some heuristics are proposed to maximize the overall data rate with low computational complexity. Finally, we validate the performances of the proposed architecture and schemes through extensive simulations.