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.