Scalable Mixed‐Dimensional Nanogenerator for the Sunlight‐Driven Water–Energy Nexus

The realization of net‐zero emissions requires high‐efficiency, solar‐driven, and sustainable technologies that can co‐generate clean water and renewable energy. We report a scalable plasma‐engineered solar thermal matrix (STM) integrating graphene quantum dots (GQDs), MXene nanosheets, and a chitosan‐based framework. Microplasma‐assisted synthesis enables hierarchical porous architectures with angstrom‐scale nanochannels, which synergistically enhance photothermal conversion, water transport, and ion mobility. The optimized STM exhibits a high photothermal efficiency of 95.7% and a solar steam generation rate of 4.2 kg m −2 h −1 under one sun. Its negatively charged nanochannels generate streaming potentials up to 200 mV in seawater, while embedded GQDs serve as photoluminescent probes for real‐time monitoring. Outdoor trials demonstrate daily desalination of ∼30 kg m −2 and stable electrical output of ∼127 mV over 9 h of solar exposure. These results establish a versatile and durable platform for decentralized water purification and energy harvesting, providing critical insights into the design of multifunctional, mixed‐dimensional nanomaterials for integrated solar‐driven systems.