Electrical engineering

Electrode

Organic chemistry

Potable water

Membrane

Hydrogen

Biology

Salinity

High-temperature electrolysis

Engineering

Electrolysis

Physical chemistry

Hydrogen production

Saline water

Chemistry

Renewable energy

Ecology

Desalination

Electrolyte

Environmental science

Electrolysis of water

Waste management

Biochemistry

Environmental engineering

Nature Energy

Powered by renewable energy sources such as solar, marine, geothermal and wind, generation of storable hydrogen fuel through water electrolysis provides a promising path towards energy sustainability. However, state-of-the-art electrolysis requires support from associated processes such as desalination of water sources, further purification of desalinated water, and transportation of water, which often contribute financial and energy costs. One strategy to avoid these operations is to develop electrolysers that are capable of operating with impure water feeds directly. Here we review recent developments in electrode materials/catalysts for water electrolysis using low-grade and saline water, a significantly more abundant resource worldwide compared to potable water. We address the associated challenges in design of electrolysers, and discuss future potential approaches that may yield highly active and selective materials for water electrolysis in the presence of common impurities such as metal ions, chloride and bio-organisms. Production of hydrogen fuel by electrolysis of low-grade or saline water, as opposed to pure water, could have benefits in terms of resource availability and cost. This Review examines the challenges of this approach and how they can be addressed through catalyst and electrolyser design.

Electrolysis of low-grade and saline surface water