Figure 7
In situ X-ray monitoring of CoOx-Pi OEC during film growth on an ITO/GCA WE with 40 µm pores. (a) Background-subtracted [electrolyte-filled reference area as indicated in Fig. 2(d)] HEXS data. HEXS patterns were collected with 2 min integration times at selected time points during continuous electrolytic CoOx-Pi film deposition from an electrolyte solution containing 0.1 M potassium phosphate, pH 7.0, and 0.5 mM Co(NO3)2·6H2O with 1.85 V (versus NHE) applied potential. The X-ray beam was defined by 0.1 mm horizontal and 0.5 mm vertical slit apertures. (b) G(r) Fourier transforms from the HEXS data in (a). The top trace shows the G(r) of CoOx-Pi powder as a reference for comparison. Noise in the HEXS patterns was attenuated using a 24-point smoothing function in the program PDFgetX2 (Qiu et al., 2004) prior to Fourier transform. The smoothing only partially removes Fourier ripple artifacts in the ensuing PDF. The high-frequency noise in the reciprocal-space data converts to non-physical pair correlations below 0.7 Å (not shown). Longer acquisition times beyond the 2 min scans used in (a) would be needed to raise the signal-to-noise and avoid these artifacts for thin CoOx-Pi films with electrolysis times shorter than 38 min. |