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In this data article, we presented the electrochemical data of the working electrode made of Co3O4 semi-transparent film. Electrochemically stable, porous nature of Kirkendall-diffusion grown Co3O4 films were applied to generate hydrogen from the seawater splitting (Patel et al., 2017) . The data presented in this article includes the photograph of prepared samples, polarization curves for water oxidation and Tafel plot, linear sweep voltammetry measurements under the pulsed light condition in 0.1 M Na2S2O3 electrolyte, and transient photoresponses with natural sea water. Moreover, seawater splitting using the Co3O4 working electrode is demonstrated.
Fig. 1 shows the photographs of the developed porous Co3O4 films on the FTO/glass substrate. Co3O4 films were masked using Kapton tape to define the working area (60 mm2) for electrochemical experimentation are shown in Fig. 1b. Polarization curve for water oxidation cycle (as shown in Fig. 2) are presented for the natural sea water. Tafel analysis is presented in Fig. 2b. Linear sweep voltammetry (LSV) measurement of the porous Co3O4 electrode was measured under a pulsed light (100 mW/cm2) condition with 0.1 M Na2S2O3 electrolyte in cathodic direction, as shown in Fig. 3. Fig. 4 shows the spectral photoresponse of Co3O4/FTO photocathode with natural sea water at over potential of 0.3 V vs RHE. Photoinduced seawater splitting using the porous Co3O4 working electrode is demonstrated in the moving clip. In this video current density is 20 mA/cm2 @ −0.8 V vs RHE.
Preparing Co3O4 electrode: Co3O4 working electrodes were prepared using the Kirkendall diffusion method . Initially the sputtered pure Co film was grown for the porous and semitransparent Co3O4 film by the heat treatment (550 °C for 10 minutes in air condition). Photographs of Co3O4 samples are shown in Fig. 1.
Electrochemical Measurements: All measurements were done using the three electrode electrochemical cells (Reference electrode: Ag/AgCl (KCl, 3 M), Counter electrode: platinum gauze, and working electrode: Co3O4/FTO/glass) attached to the Potentiostat/Galvanostat (PG-stat) (WonA Tech, ZIVE SP1). Linear sweep voltammetry was applied to measure the anodic polarization and photocathode properties. Chronoamperometry technique was applied to measure the transient photoresponses at an applied potential of 0.33 V vs RHE in the natural seawater. The white light (5800 K, Bridgelux, ES Star Array, BXRA-56C0700-A) was applied for photoinduced electrochemical measurement. This was calibrated by a power meter (KUSAMMECO, KM-SPM-11). The illuminating light source was calibrated for one-sun light intensity (100 mW/cm2) and was applied in the pulse mode or the continuous mode. For transient photoresponses, a monochromatic light source of wavelength 365 nm (2 mW/cm2), 460 nm (3 mW/cm2), 520 nm (6 mW/cm2), and 620 nm (15 mW/cm2) were applied to working electrode from the front direction.
This research was supported by Basic Science Research Program through the National Research Foundation (NRF) of Korea by the Ministry of Education (NRF-2015R1D1A1A01059165), Korea Research Fellowship Program through the NRF by the Ministry of Science, ICT and Future Planning (NRF-2015H1D3A1066311) and Korea Institute of Energy Technology Evaluation and Planning by the Ministry of Knowledge Economy (KETEP-20168520011370)