The integration of ionic power generation with solar-driven water evaporation presents a promising solution to the critical global problems of freshwater scarcity and clean energy deficiency. In this work, a scalable normal temperature chemical vapor deposition (CVD) method is applied for the first time to the fabrication of a cellulose@polypyrrole (CC@PPy) membrane with efficient ionic power generation performance. The excellent ionic power generation is intimately related to the water and thermal gradients across the membrane, which not only induces fast water evaporation but also synergistically promotes the transport of counterions in charged nanochannels, and the corresponding mechanism is attributed to the streaming potential resulting from the ionic electrokinetic effect and the ionic thermoelectric potential originating from the Soret effect. Under one sun illumination, the CC@PPy film can produce a sustained voltage output of ~ 0.7 V and a water evaporation rate up to 1.67 kg m-2 h-1 when an adequate water supply is available. This study provides new methods for the scalable fabrication of ionic power generation membranes and a design strategy for high-performance solar power generators.