U.S. startup exceeds 10% solar-to-hydrogen efficiency with 100 cm² module

Iowa-headquartered photoelectrochemical technology company SunHydrogen has achieved solar-to-hydrogen (STH) conversion efficiencies of more than 10% with its 100 cm² hydrogen modules during preliminary testing at Sparc Hydrogen’s laboratories, according to a company statement.

The latest performance follows earlier testing of SunHydrogen’s 100 cm² modules at the R&D facilities of Japanese automaker Honda, where the devices achieved an active-area STH efficiency of 10.8%. Honda and SunHydrogen have been working under a joint development agreement aimed at advancing the technology toward an installation-ready hydrogen panel and cost-effective commercial production.

“SunHydrogen’s system is an integrated semiconductor-electrocatalyst architecture in which the light-absorbing semiconductor, purpose-designed contacts and water-splitting catalysts are engineered to operate together as a single hydrogen-generating module,” SunHydrogen Business Director Tor Erik Hoftun told pv magazine. “When sunlight is absorbed, the semiconductor generates electrons and holes. Purpose-designed contacts route these photogenerated charge carriers to integrated hydrogen- and oxygen-evolution catalysts. The electrons drive the production of hydrogen, while the holes drive the production of oxygen.”

Unlike a conventional PV module, whose cell layout and electrical contacts are designed primarily to deliver power to an external circuit, such as a separate electrolyzer stack, SunHydrogen’s semiconductor module is engineered specifically for direct solar-to-hydrogen conversion.

“In PV terms, the semiconductor’s current-voltage characteristics are matched to the electrochemical load so that the coupled module operates at a point that maximizes the conversion of incident solar energy into chemical energy stored in hydrogen,” Hoftun said.

“The hydrogen-generating module operates inside a reactor housing that manages electrolyte circulation and the collection and handling of the hydrogen and oxygen produced,” he added. “Because the photovoltaic and electrochemical functions are directly coupled, the architecture does not require a separate electrolyzer stack and can avoid much of the power-conversion equipment normally used. At the pilot and system level, auxiliary balance-of-system components are still used for electrolyte circulation, gas handling, monitoring, controls and safety.”

Following the recent test results, SunHydrogen entered into an agreement with Australia-based Sparc Hydrogen, which is developing a process that uses concentrated sunlight, water and a photocatalyst to produce hydrogen without an electrolyzer. The companies plan to assess the integration of SunHydrogen’s modules into Sparc Hydrogen’s reactors, with the aim of reducing hydrogen production costs.

“Under the 24-month Sparc Hydrogen collaboration, laboratory testing under concentrated sunlight is expected to progress, subject to technical milestones, to on-sun testing at Sparc Hydrogen’s Sharp facility in South Australia and an assessment of levelized hydrogen cost, with a potential pathway to a module-supply or manufacturing-license agreement,” Hoftun said.

He added that SunHydrogen is working with CTF Solar and other manufacturing partners to support the development of higher-efficiency products with Honda R&D.

In addition to testing at the 100 cm² scale, SunHydrogen has achieved efficiencies approaching 9% with a 1.92 m², PV-sized development module in outdoor testing.

“Subject to extension of the joint development program with Honda R&D, the next development phase is expected to advance the module architecture toward active-area solar-to-hydrogen efficiencies approaching 15%, with a focus on translating higher efficiency to larger, manufacturable modules,” Hoftun said.