The method turns sugars from biomass (such as agricultural waste cellulose) into hydrogen and another useful chemical, formate, at the same time, the researchers said.

This could be cheaper and may use less energy than standard solar electrolysis that only splits water, because the sugar oxidation replaces the energy-intensive oxygen evolution reaction typically required at the anode.

The findings from the Singapore Energy Center, Singapore Ministry of Education Academic Research Fund, National Research Foundation Singapore, and the National Natural Science Foundation of China were published in the eScience journal.

The teams used a copper-doped cobalt catalyst to steer sugar reactions so that they require less energy than traditional oxygen evolution reactions in electrolysis.

According to the researchers, the reaction was run in a membrane-free reactor powered by sunlight, producing over 500 micromoles of hydrogen per hour per square centimetre of active surface.

While this level of output is small in absolute terms, the researchers are benchmarking reaction efficiency rather than total hydrogen production, with results reported per unit area as is standard for early-stage electrochemical systems.

It is also a relatively high production rate per unit area. This points to the potential for scaling solar-driven co-electrolysis systems that combine green hydrogen production with biomass upgrading.

Similar laboratory-scale studies have explored the use of alcohols and other organic feedstocks to reduce the energy demand of electrolysis, but many rely on external electricity rather than fully solar-driven operation.

However, the technology remains at an early stage. Challenges remain around long-term catalyst stability, operation under variable real-world sunlight conditions, and the use of more complex, less purified biomass feedstocks.

Even so, the approach is based on solid catalysts and sunlight, both of which are inherently scalable. The membrane-free design could also help reduce system cost and complexity if the process can be translated beyond the laboratory.