Toward accelerated stress testing and operando distribution of relaxation times diagnostics for durability assessment of a 120 cm² CO₂ (photo)electrolyzer
Journal of CO2 Utilization (111)
by Federica Zammillo, Hilmar Guzmán, Simelys Hernández (Department of Applied Science and Technology (DiSAT), Politecnico di Torino); Nigel Patterson, Julian Rosas (Pulsenics Inc); Babu Radhakrishnan, Fatwa F. Abdi (Institute for Solar Fuels, Helmholtz-Zentrum Berlin für Materialien und Energie), Adriano Sacco, Angelica Chiodoni (Istituto Italiano di Tecnologia), Eduard Alexandru Morosanu, Massimiliano Antonini (Hysytech)
Abstract
Solar-driven CO₂ reduction technologies face unique challenges when transitioning from laboratory to prototype scale. Within the European Union-funded SunCoChem project, a photoelectrochemical reactor was designed and validated for CO₂ conversion to a CO-rich syngas stream, scalable to 2400 cm², for subsequent upgrading in a
hydroformylation unit. Beyond selectivity, ensuring process durability is critical for economic viability, yet degradation pathways are difficult to identify at the prototype scale, where conventional gas-product analysis provides only delayed and indirect information. Here we couple operando electrochemical impedance spectroscopy (EIS) with distribution of relaxation times (DRT) analysis on a 120 cm² BiVO₄-photoanode/Cu₂O–SnO₂-cathode device, and combine it with targeted stress testing, to resolve and monitor failure modes in real time. The prototype sustained CO-dominant operation for over 200 h at 6.1 mA cm⁻², with average Faradaic efficiencies of ~81% to CO and ~10% to H₂ and a solar-to-chemical efficiency of 4.3–5.0%. DRT resolved distinct impedance signatures associated with gas-chamber overpressure, GDE flooding and photoanode degradation, providing a non-invasive diagnostic framework. We discuss the current technological bottlenecks and outline strategies for further optimization and scale-up.