6 Search Results

An XY segmented cell was developed for low temperature PEM water electrolysis (PEMWE). The system can assess the local performance by enabling in situ measurements of spatial currents and impedances. In this work, we show through experiments, as well as through modelling work, that the porous transport layer (PTL) must be segmented to eliminate crosstalk. Accurate measurements are only possible when crosstalk is fully eliminated. The XY segmented cell is applied to a case study characterizing the impact of a PTL platinum coating void on spatial performance. The localized performance impact of the coating void is found to be orientationmore » specific: coating voids facing the catalyst layer reduce performance significantly more than coating voids facing the flow field. The results suggest that the tolerances for PTL coating uniformity can be lower at the side facing the flow field. The work showcases the feasibility of the XY segmented cell for impact assessment studies. The presented XY segmented cell enables the characterization of spatial phenomena in PEMWE devices and is envisioned to support modeling efforts and the investigation of manufacturing related tolerances for mass produced PEMWE devices.« less

This work demonstrated a robust, scalable cell architecture for electroreduction of CO₂ (CO₂R). An up to 90% faradaic efficiency for the conversion of CO₂R to formate at 500 mA/cm² was realized at a 25 cm2 gas diffusion electrode (GDE) with a carbon-supported SnO₂ electrocatalyst. Furthermore, a 1.27 mm thick catholyte was used between the bipolar membrane and cathode GDE, which could be further reduced to tens of micrometers upon refinement. The deconvolution of the potential drop from each individual component/process guides the pathways to higher energy efficiencies of CO₂R at this platform. Significant changes in the agglomerate size and aspectmore » ratio on the electrode before and after an 11 h test were revealed by nano-CT, suggesting reduced CO₂ accessibility from electrode degradation. The versatility of this CO₂R testing platform enables the ability to assess materials, components, and interactions at scales more in line with future devices.« less

Photoelectrochemical (PEC) water splitting is an elegant method of converting sunlight and water into H₂ fuel. To be commercially advantageous, PEC devices must become cheaper, more efficient, and much more durable. This work examines low-cost polycrystalline chalcopyrite films, which are successful as photovoltaic absorbers, for application as PEC absorbers. In particular, Cu-Ga-Se films with wide band gaps can be employed as top cell photocathodes in tandem devices as a realistic route to high efficiencies. In this report, we demonstrate that decreasing Cu/Ga composition from 0.66 to 0.31 in Cu-Ga-Se films increased the band gap from 1.67 to 1.86 eV andmore » decreased saturated photocurrent density from 18 to 8 mA/cm² as measured by chopped-light current-voltage (CLIV) measurements in a 0.5 M sulfuric acid electrolyte. Buffer and catalyst surface treatments were not applied to the Cu-Ga-Se films, and they exhibited promising stability, evidenced by unchanged CLIV after 9 months of storage in air. Finally, films with Cu/Ga = 0.36 (approximately stoichiometric CuGa₃Se₅) and 1.86 eV band gaps had exceptional durability and continuously split water for 17 days (~12 mA/cm² at -1 V vs RHE). This is equivalent to ~17 200 C/cm², which is a world record for any polycrystalline PEC absorber. These results indicate that CuGa₃Se₅ films are prime candidates for cheaply achieving efficient and durable PEC water splitting.« less