Charge-engineered biomass enables concurrent salt rejection and antibacterial performance toward efficient and sustainable interfacial solar desalination

Recently, the development of hydrogel-based solar vapor generators (SVGs) has greatly promoted the applications of solar-driven interfacial desalination (SID) technology toward practical freshwater generation. Nevertheless, the hydrogel SVGs are facing risks of microbial contamination as well as retarded water generation performance in high-salinity brine. Herein, a charge engineering concept is proposed for developing SVG with concurrent strong salt rejection and antibacterial performance toward sustainable SID in high-salinity brine. The SVG is composed of polyhexamethylene guanidine hydrochloride (PHMG) groups grafted starch chains, and poly(vinyl alcohol) (PVA) networks with distributed coal powders as solar absorbents. The introduced positively charged PHMG aids in enhancing the Donnan effect in the hydrogel, accelerating liquid transport while minimizing the local salt concentrations, therefore the obtained SVG retains strong salt-rejection capabilities. Compared with bare starch constructed hydrogel composite, the hydrogel with engineered PHMG can spontaneously avoid salt accumulation and exhibit sustainable highly efficient solar desalination performance in nearly saturated saline (20 wt% NaCl) for over 2 weeks (with an average evaporation rate of 2.21 kg · m −2 · h −1 under one sun irradiation). Additionally, the intrinsic broad-spectrum antibacterial properties of the quaternary ammonium groups enable prominent inhibitory performance against typical Escherichia coli ( E. coli ) and Staphylococcus aureus ( S. aureus ). It is envisioned that the charge engineering strategy could promote the practical applications of SID technology toward sustainable and scalable freshwater production in high salinity brine.