The dual global challenges of freshwater scarcity and clean energy transformation urge innovative, sustainable solutions. Seawater, as an abundant resource in Hong Kong, offers a promising avenue for both desalination and hydrogen production. We share two cases of advanced biomass-derived materials and devices here to enable efficient seawater desalination and sustainable hydrogen generation, leveraging renewable resources and green chemistry.
A sustainable, self-floating wood-based evaporator is constructed via in-situ Ni-P electroless plating and surface graphite spray coating (Fig.1). The device aims to continuously produce distilled water by utilizing solar energy, which minimizes diurnal variations in solar irradiance through a secondary Joule-heating mode. The extraordinary joule-heating behaviour of the deposited Ni-P alloy localizes interfacial heat, while the hierarchical wood structure reduces evaporation enthalpy, thereby maximizing the evaporation efficiency. This design leverages the mesoporous structure and low anisotropic thermal conductivity of wood. Furthermore, this project demonstrates potential for scaling up devices to all-weather 3D evaporators.
Fig.1 Illustration of a seawater desalination device based on natural resources. (a) Schematic demonstration for the synthetic process of the round-the-operation interfacial evaporator; (b) Actual setup for outdoor test; (c) Overall device sustainability footprint analysis (Ref.1).
In the second case, natural wool fibres, rich in disulphide bonds within keratin, serve as a sustainable precursor for high-performance electrocatalysts (Fig.2). Through reduction, carbonization, and activation, we synthesized nitrogen/phosphorus co-doped active carbons supporting high cobalt sulphide content (Co₉S₈-N,P doped active carbons) without additional sulphur sources. The advantages of electrocatalysts enable the rapid upgrade of seawater for green H2 generation, as well as provide a new sustainable pathway to close the life cycle in the textile industry.
Fig.2 Sustainable H2 production by seawater splitting reaction on waste cloth-derived electrode. (a) Schematic demonstration of carbonized wool fibre for seawater splitting reaction; (b) Potential waste cloth resources for electrode; (c) Optical image of chemical treated wool fibre before carbonization; (d) Scanning electron microscopy of wool fibre after carbonization (insert: crystal structure of Co9S8 catalysts) (Ref. 2).
Looking ahead…
By combining waste textile/leather derived electrocatalysts and wood based solar evaporators, this approach enables the direct utilization of seawater for both clean water and sustainable hydrogen fuel. The use of renewable, low-cost biomass/textile/leather resources and scalable fabrication methods underscores the potential for large-scale, environmentally friendly deployment. These innovations pave the way for solutions in coastal and resource-limited regions.
