High performance of interfacial solar-driven water evaporation and power generation by ZIF-8 derived N-doped porous carbon polyhedron

Water evaporation-based power production and interfacial solar steam generation are considered as the biggest promising techniques for resolving global freshwater and energy issues. Nevertheless, it remains challenging to construct solar evaporators for superior electrical energy generation and high evaporation flux at the same time; besides, the impact of the surface charge on the effectiveness of water evaporation power generation is unclear. Herein, we report the preparation of zinc-based metal–organic frameworks (ZIF-8) by ball milling and the controllable carbonization of ZIF-8 to prepare N-doped porous carbon polyhedron (NDPCP). Subsequently, a solar evaporator and energy harvesting device based on NDPCP is prepared to produce freshwater and generate electricity. The NDPCP evaporator has good hydrophilicity, high sunlight, strong photothermal conversion capability, and low enthalpy of vaporization. The conversion efficiency is 90.9 % and the evaporation rate is 2.86 kg m⁻² h⁻¹. By using the NDPCP-700 evaporator-based power generating unit, an indoor open circuit voltage of 202 mV is generated. In the outdoor, the NDPCP-700 evaporator realizes the freshwater production of 3.01 kg m⁻² and open circuit voltage of 351 mV. We demonstrate that power production requires high specific surface area, many functional groups, and well-developed pore channels. Positively charged ions are inhibited in positively charged nanochannels, according to molecular dynamics (MD) results, which causes a possible distinction between the top and bottom ends. This study not only reveals the feasibility of interfacial solar evaporators constructed from materials with positive surface charges, but also provides opportunities for developing advanced freshwater electricity co-generation devices.