Covalent tensor hydrogel using a self-semisacrificing strategy for effective photothermal steam generation

Abstract

Widespread access to solar-driven steam generation requires monolithic structures with enhanced light absorption, water transportation, and heat allocation. However, the precise assembly of building blocks necessary for this integration remains a considerable challenge. This study develops a superior covalent tensor hydrogel (CTH) consisting of microgels prepared using a microfluidic device. Our self-semisacrificial approach employs chitosan and polyethene glycol as linkers to automatically assembly their microgels, which can be further precisely regulated through ultrasonic treatment and ultraviolet irradiation. The hierarchically porous CTH features a rough upper layer that enhances light absorption and a hierarchically porous hydrogel matrix that localizes heat, promoting energy absorption and thermal management. This design enhances interfacial solar light absorption and thermal insulation, with a low thermal conductivity of 0.3 W m⁻¹ K⁻¹, achieving a maximum evaporation rate of 3.1 kg m⁻² h⁻¹. The vertical distribution of microgels within CTH creates a gradient capillary force, effectively driving water transport to the interface and enabling self-cleaning properties for prolonged effective water evaporation. This CTH monolith represents a highly effective replacement for current hydrogels in effective green solar energy usage.