The amount of iridium required to electrolyse green hydrogen has been drastically reduced, a breakthrough that is a significant boost for the upcoming green hydrogen economy, as well as South African platinum group metals (PGMs) mining.

Heraeus Precious Metals has achieved a material thrifting success with its new electrocatalyst, which requires only a fraction of the iridium previously required by proton exchange membrane (PEM) electrolysers, which split water into hydrogen and oxygen.

“We took up the challenge to come up with new iridium catalysts for PEM electrolysers,” Heraeus Precious Metals executive VP: new business development and innovation Philipp Walter told Engineering News & Mining Weekly in a Zoom interview.

Iridium, one of the six elements of PGMs, plays a key role as a catalyst on the anode side of PEM electrolysers and what Heraeus did was acknowledge very early that there was a need to be more cost effective with iridium catalysts and for lower-iridium-containing catalysts to make PEM electrolysis work at the scale foreseen.

The new Heraeus catalyst not only contains significantly less iridium but has far higher catalyst performance at lower cost.

However, if left to conventional catalysts, the global availability of the mainly South African-supplied iridium would have been insufficient to meet the targets of the European Union Commission, which has a strategy that will drive demand for 40 GW of electrolyser capacity by 2030.

The standard iridium electrocatalyst uses iridium black, a finely divided iridium powder that can be used as a precursor for iridium oxide and as a catalyst in hydrogen sulphide sensors and fuel cells.

A high 1 g/kW to 2 g/kW of iridium black is required for standard PEM electrolysers, but Heraeus Precious Metals has succeeded in slashing the iridium required to as little as 0.3 g/kW to 0.4 g/kW for the new ultra-low-iridium-loaded electrocatalysts for PEM electrolysis.

Nevertheless, iridium recycling remains pivotal: “We’re in the midst of defining our recycling strategies with key stakeholders in the industry,” Walter told Engineering News & Mining Weekly.