Fig. 5. Performance in alkaline water electrolyser.
a, b Polarization curve, mass activity (a) and electrochemical impedance spectra (b) for catalyst-coated diaphragm electrolyser compared with separated electrode and diaphragm electrolyser. Raney Ni was used as catalyst with loadings of 2 mg cm−2 and 26–30 mg cm−2 for the catalyst-coated diaphragm and mesh electrode, respectively. All polarization curves are without iR correction. Error bars in the polarization curve of the catalyst-coated diaphragm electrolyser is obtained by evaluation of four samples, and the average voltage at each current density is presented with standard deviation indicated. Mass activity was calculated with the current density at voltage of 1.8 V. The electrochemical impedance spectra were profiled at current density of 0.5 A cm-2. c, d Polarization curves (c) and their Tafel equation fitting (d) for catalyst-coated diaphragms with various catalysts. The catalyst loading was controlled at 2 mg cm-2 for RuO2, Ni-Fe layered double hydroxide (NiFe-LDH) and Raney Ni. For carbon supported Pt (Pt/C), the Pt loading was 0.1 mg cm-2. For Tafel equation fitting, the cell voltage was corrected by subtracting the voltage drop caused by the ohmic resistance (iR).