Bio-inspired Micropit Photothermal Evaporator by 3D Printing for Efficient Water-Electricity Co-generation

Solar-driven interfacial evaporation provides a sustainable approach for water purification and energy harvesting, but integrated evaporators still face challenges in rapid fabrication, efficient solar-energy utilization, and stable hydrovoltaic output. Herein, a beetle-inspired CTPH evaporator with biomimetic micropit arrays was rapidly fabricated by digital light processing (DLP) 3D printing within 38 min. Incident light can undergo multiple internal reflections within the concave micropits. The three-dimensional architecture also enlarges the exposed geometric evaporation area. MWCNTs-COOH act as photothermal centers and introduce negatively charged interfaces favorable for hydrovoltaic electricity generation. Under 1 sun irradiation, the optimized CTPH evaporator achieved an evaporation rate of 2.09 kg m-2 h-1 and a solar-to-vapor conversion efficiency of 95.4%. In brine, it delivered a stable open-circuit voltage of 0.37 V and a steady-state current of 13.26 μA; after scaling the array to 4 × 4, the current increased to 61.45 μA. The evaporator also showed effective purification performance toward seawater, heavy-metal wastewater, dye wastewater, and acidic/alkaline solutions, demonstrating its feasibility for integrated solar water purification and hydrovoltaic electricity generation.