Solar co-electrolysis process converts biomass sugars to low cost green hydrogen

by Riko Seibo
Tokyo, Japan (SPX) Jan 05, 2026

Researchers in China and Singapore have demonstrated a solar-powered co-electrolysis route that produces hydrogen at projected costs below fossil-based hydrogen while upgrading biomass-derived sugars into formate. The system couples water electrolysis with selective oxidation of glucose on a copper-doped cobalt oxyhydroxide catalyst, which lowers the anodic potential by nearly 400 mV and enables hydrogen production rates above 500 micromoles per hour per square centimeter in a membrane-free reactor. By using low-cost sugars obtained from non-food cellulose feedstocks and converting them into value-added chemicals during hydrogen generation, the process increases energy efficiency and improves the economics of solar fuels.

Solar-driven water electrolysis is a key pathway for producing hydrogen without direct carbon emissions, but the oxygen evolution reaction requires high energy input and raises operating costs. Biomass-derived sugars offer an alternative oxidation route that proceeds at lower potentials and yields chemical products, yet controlling glucose conversion to a single target such as formate has been difficult. The study addresses this challenge by designing a catalyst that steers glucose through a defined reaction pathway, enabling selective and energy-saving oxidation that can be integrated with hydrogen production.

A team from China Agricultural University and Nanyang Technological University reported that a copper-modified cobalt oxyhydroxide catalyst can convert glucose cleanly to formate while sustaining high hydrogen output when powered by an InGaP/GaAs/Ge triple-junction photovoltaic device. In a membrane-free co-electrolysis configuration, the photoelectrochemical system produces over 500 micromoles per hour per square centimeter of hydrogen, driven by a catalyst-guided cascade oxidation mechanism. This mechanism lowers the electrical energy input required and supports simultaneous biomass upgrading and solar hydrogen generation.

To identify a suitable anode material, the researchers compared several earth-abundant metal oxyhydroxides and selected cobalt oxyhydroxide as a promising platform for glucose oxidation. They then introduced different dopants and found that adding 5 mol percent copper transformed cobalt oxyhydroxide into a more selective and efficient electrocatalyst. With copper incorporation, the formate yield increased from 50 percent to 80 percent and the onset potential for glucose oxidation decreased by about 400 millivolts in alkaline solution, enabling more energy-efficient co-electrolysis while maintaining high reaction rates.

The team applied X-ray photoelectron spectroscopy, Raman spectroscopy, electron microscopy and in situ impedance analysis to examine how copper modifies the catalyst surface and electronic structure. These measurements showed that copper stabilizes reactive Co3+ sites and suppresses Co4+ species that tend to drive non-selective bond cleavage. Density functional theory calculations indicated that copper doping disfavors side-on adsorption of glucose and reduces beta-cleavage pathways that generate by-products, while promoting end-on binding at the aldehyde group and a stepwise alpha carbon - carbon cleavage sequence that releases formate from each carbon atom in the sugar.

On the cathode side, pairing the copper-doped cobalt oxyhydroxide anode with an earth-abundant Ni4Mo electrode enabled a membrane-free cell that produces high-purity hydrogen with nearly 100 percent Faradaic efficiency. Under concentrated sunlight, the device delivered a hydrogen generation rate of 519.5 +/- 0.4 micromoles per hour per square centimeter and maintained stable performance over 24 hours of continuous operation. The high selectivity toward formate at the anode and the efficient hydrogen evolution at the cathode demonstrate the technical feasibility of integrating biomass reforming with solar hydrogen production in a single system.

One of the study's senior researchers noted that the findings illustrate how the catalyst design can reshape both the efficiency and economics of solar hydrogen production. By orchestrating glucose oxidation through a highly selective alpha-cleavage pathway, the catalyst reduces the electrical energy required while upgrading biomass into a chemical feedstock. The researcher emphasized that this dual-function system shows how renewable hydrogen generation can be directly coupled with biomass valorization in a unified electrochemical process.

The co-electrolysis strategy described in the report offers a potential route to scalable and cost-competitive green hydrogen by combining reduced energy demand with revenue from formate as a co-product. Economic modeling in the study suggests that the levelized cost of hydrogen could decline to about $1.54 per kilogram, which is comparable to or lower than hydrogen produced from fossil fuels. The membrane-free design simplifies the system architecture and lowers capital requirements, and the catalyst performs effectively on hydrolysates derived from agricultural waste, indicating compatibility with real biomass streams and possible deployment in distributed hydrogen production and circular bioeconomy applications.

Research Report:Steering the adsorption modes and oxidation state of Co oxyhydroxide active sites to unlock selective glucose oxidation to formate for efficient solar reforming of biomass to green hydrogen