The US Department of Energy (DOE) has announced more than $19m in funding for research and development into solar photocatalysis — an experimental method of producing green hydrogen without the use of electrolysers or solar photovoltaic panels — as part of an effort to reduce the cost of clean H2 to $1/kg by 2031.

Hydrogen: hype, hope and the hard truths around its role in the energy transition
Will hydrogen be the skeleton key to unlock a carbon-neutral world? Subscribe to the weekly Hydrogen Insight newsletter and get the evidence-based market insight you need for this rapidly evolving global market

It is hoped that the technology — in which water molecules are split directly using sunlight and/or heat from the sun with the help of a catalyst — could prove more cost-efficient than using solar panels and electrolysers to produce green hydrogen, in which 70-80% of the H2 cost is down to the electricity input.

The most prominent developer of photocatalysis technology to date has arguably been Spanish company Sunrgyze — a joint venture between oil giant Repsol and natural-gas transmission company Enagas — which plans to build a demonstration photoelectrocatalysis plant in 2025.

The DOE has allocated about $1m each to ten US universities, plus French multinational Saint-Gobain’s unit in Massachusetts, as well as $8.3m to the HydroGEN Laboratory Consortium, made up of national research laboratories, to provide technical assistance to the 11 photoelectrochemical and solar thermochemical water splitting research projects.

A further $8.6m is due to be invested into the development and validation of sensors to monitor and measure hydrogen leakage throughout the value chain, including $1.5m for a project run by industrial giant GE.

Research published in the past year suggests that H2 leaks could indirectly worsen global warming in the short-term by prolonging the lifetime of greenhouse gases such as methane, which is more potent but shorter-lived in the atmosphere compared to CO2.

A schematic representation of a solar photocatalysis system. Photo: Acar et al, Journal of Power Sources (2016)

Rio Tinto suggested in December last year that storage as a liquid, which could require venting of an estimated 1% of boil-off per day, could make hydrogen “potentially more damaging to use than burning natural gas” due to this effect.

Figures from US non-profit the Environmental Defense Fund indicate that while the best-case leakage rate may only be 1%, it could be as high as 10%. The advocacy group, which has worked with equipment manufacturer Aerodyne Research to develop its own hydrogen leakage sensor, argues that technology that is currently on the market only looks for large leaks that represent a safety hazard, while smaller, parts-per-billion concentrations of H2 are missed.

In addition, the DOE has also allocated $4.5m to two hydrogen storage demonstration projects, which will study the use of metal hydrides and formic acid as potential mediums.

Another $9m is to be invested in research projects developing catalysts and membrane-electrode assemblies that have a low concentration of platinum group metals — such as platinum and iridium — for use in fuel-cell trucks. This includes $3m to an R&D initiative run by automaker General Motors.

However, the small print shows there is no guarantee that the money will actually be handed out to these programmes.

“Selection for award negotiations is not a commitment by DOE to issue an award or provide funding,” the DOE points out in a document detailing all the projects. “Before funding is issued, DOE and the applicants will undergo a negotiation process, and DOE may cancel negotiations and rescind the selection for any reason during that time.”