Comparative techno-economic and life-cycle analysis of precious versus non-precious metal electrocatalysts: the case of PEM fuel cell cathodes

Sluggish kinetics in the oxygen reduction reaction (ORR) require significant quantities of expensive Pt-based nanoparticles on carbon (Pt/C) at the cathode of proton exchange membrane fuel cells (PEMFCs). This catalyst requirement hinders their large-scale implementation. Single atom Fe in N-doped C (Fe-N-C) electrocatalysts offer the best non-Pt-based ORR activities to date, but their environmental impacts have not been studied and their production costs are rarely quantified. Herein, we report a comparative life-cycle assessment and techno-economic analysis of replacing Pt/C with Fe-N-C at the cathode of an 80 kW PEMFC stack. In the baseline scenario (20 g(Pt/C)vs. 690 g(Fe-N-C)), we estimate that Fe-N-C could reduce damages on ecosystems and human health by 88-90% and 30-44%, respectively, while still increasing global warming potential by 53-92% and causing a comparable impact on resource depletion. The environmental impacts of Pt/C predominantly arise from the Pt precursor while those of Fe-N-C are presently dominated by the electricity consumption. The monetized costs of environmental externalities for both Fe-N-C and Pt/C catalysts exceed their respective direct production costs. Based on catalyst performance with learning curve analysis at 500 000 PEMFC stacks per annum, we estimate replacing Pt/C with Fe-N-C would increase PEMFC stack cost from 13.8 to 41.6 USD per kW. The cost increases despite a reduction in cathode catalyst production cost from 3.41 to 0.79 USD per kW (excluding environmental externalities). To be cost-competitive with a Pt-based PEMFC stack delivering 2020 US Department of Energy target of 1160 mW cm(-2) (at 0.657 V), the same stack with an Fe-N-C cathode would need to reach 874 mW cm(-2), equivalent to a 200% performance improvement. These findings demonstrate the need for continued Fe-N-C activity development with sustainable synthesis routes in mind to replace Pt-based cathode catalyst in PEMFCs. Based on forecasting scenarios of fuel cell vehicle deployment targets, we find that Pt consumption would be constrained by Pt supply.

Automated summary

This study compares the environmental impacts and economic analysis of using non-Pt-based electrocatalyst Fe-N-C to replace Pt/C in PEMFCs. The findings show that Fe-N-C can reduce environmental damages and human health impacts, but it still faces issues such as electricity consumption and resource depletion. The cost of PEMFC stacks with Fe-N-C cathode would increase compared to those with Pt/C cathode due to the increase in environmental externalities. Continued improvement of Fe-N-C performance is necessary to replace Pt-based cathode catalysts in PEMFCs.