Other factors which also affect the PEC activity and stability are film thickness and crystallite grain size. Photoelectrochemical (PEC) studies reveal an unexpected trend, where the highest PEC activity appears to correlate with the amount of Cu 2+ content. Specifically, we employ high resolution XANES for thorough quantitative analysis of the Cu 2O films, alongside more common characterisation methods like XRD, SEM and Raman spectroscopy. In this work, we take a systematic look into electrochemically deposited Cu 2O and investigate the impact of deposition parameters towards the bulk and surface chemistry of the deposited film. A variety of Cu 2O films reported by many research groups would often display vastly different electronic properties and catalytic activity, while appear indistinguishable under common characterisation tools. However, structural descriptors, linking electrodeposition parameters, film structure and the catalytic properties are elusive. Electrodeposition is commonly used to deposit Cu 2O films on conductive substrates due to its simplicity and consistency. Above a linear gas flow velocity of 70 cm s −1, the deposition rate was constant, which indicated a surface-controlled process.Ĭu 2O is an attractive photocathode for important renewable energy reactions such as water splitting and CO 2 reduction. At 650 ☌ and with an excess of CuI, the deposition rate was found to be controlled by the decomposition of N 2O. Cu 2O films were also deposited with N 2O as the oxygen source. For higher / ratios, the CuO phase was stable, even at a low O 2 pressure. The formation of CuO was also investigated thermodynamically. When I 2 was added to the reaction gas mixture, the maximum disappeared and the deposition rate increased. The maximum was attributed to a change in the deposition mechanism upon the formation of CuO. The CuO phase was obtained at a certain position in the CVD reactor and a sudden maximum in the deposition rate was then reached. Cu 2O was deposited at low O 2 partial pressures ( P o 2 < 0.2 Torr) in a long isothermal hot wall chemical vapour deposition (CVD) reactor ( T=500 ☌). If O 2 was used, both CuO and Cu 2O were obtained. Thin films of CuO and Cu 2O were deposited from CuI as the copper source and O 2 or N 2O as the oxygen source.
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