Water scarcity poses a critical global challenge, particularly in arid and off-grid inland regions. Solar-driven atmospheric water harvesting (SAWH) offers a promising solution to freshwater shortages; however, existing systems are hindered by two key limitations: suboptimal material adsorption/desorption performance and inefficient thermal management in device design. To address these challenges, this study presents a hydrogel composite-based SAWH device featuring an optimized thermal insulation structure. The composite sorbent, rGO@Cur-LiCl-synthesized by integrating reduced graphene oxide (rGO) with lithium chloride (LiCl) and bioderived curdlan (Cur)-exhibits exceptional adsorption-desorption kinetics and high water uptake capacities of 1.74 and 3.01 g g- 1 at 30 % and 60 % relative humidity (RH), respectively. The designed passive SAWH device incorporates a dual-chamber thermal insulation configuration, a dual-layer acrylic radiative-convective barrier, and a modular adsorbent bed, enabling two full daily cycles. Under one-sun irradiation at 30 degrees C and 30 % RH, the system achieves a remarkable water yield of 2.33 L m- 2 day- 1, outperforming state-of-the-art counterparts by 2-5 times. This work advances a sustainable strategy for decentralized freshwater production in water-scarce regions.