Preparation of gradient heterogeneous hydrogels by Pickering emulsion templating method and its trifunctional coupling of photothermal–evaporation–power generation

Abstract

Solar-driven interfacial evaporation technology holds significant potential, as evaporation-induced hydropower generation can directly convert ambient thermal energy into electrical energy, thereby addressing both freshwater scarcity and the global energy crisis. In this study, a hydrogel-based solar interfacial evaporator—comprising carboxymethyl cellulose (CMC), cellulose nanofibers (CNF), carbon nanotubes (CNT), and polypyrrole (PPy) integrated within a polyacrylamide (PAM) matrix—is developed using Pickering emulsion polymerization. The system leverages nanofibrillar cellulose-assisted CNT and PPy as emulsion stabilizers to effectively tackle the dual challenge of freshwater production and electricity generation. The resulting MFTP-PAM hydrogel evaporator exhibits enhanced light absorption and photothermal conversion efficiency, enabling concurrent solar-driven water evaporation and thermoelectric power generation. Under one sun irradiation, the optimized evaporator achieves a high evaporation rate of 1.53 kg m⁻² h⁻¹ in tap water and generates an output voltage of 470 mV in a 3.5 wt% NaCl solution. Furthermore, the MFTP-PAM hydrogel evaporator can desalinate and prevent contamination. This study aims to propose a simple and reliable modification method to enhance the evaporation performance of Pickering-based hydrogel evaporators and to improve their hydrogel network structure to produce both clean water and electricity, which is a promising energy solution.