Glycine-nitrate derived cobalt-doped BiPO4: An efficient OER catalyst for alkaline electrochemical cells

The investigation of cost effective and earth abundant electro-catalyst to catalyze oxygen evolution reaction (OER) is highly desirable for the development of future sustainable energy. Herein, a facile one step glycinenitrate decomposition method has been proposed to synthesize crystalline un-doped and cobalt doped BiPO4. The prepared un-doped and cobalt doped BiPO4 have been evaluated as potential electro-catalysts for OER. The XRD, XPS and ICP-OES results reveal that BiPO4 undergo surface reconstruction during OER and thereby converted into Bi2O3. Thus, the in situ formed Bi2O3 is the real active catalyst to catalyze OER where 5% cobalt doped BiPO4 exhibits excellent OER activity in terms of low overpotential of 328 mV and 394 mV to afford the current density of 10 and 50 mA cm(-2) respectively, which is much lower than that of the un-doped BiPO4 (480 mV). Besides, the polarization curves of 5% cobalt doped BiPO4 shows negligible difference in overpotential even after 20 h of continuous electrolysis, demonstrating excellent stability in alkaline KOH. This work demonstrates intrinsic electro-catalytic activity of phosphate based electro-catalyst can be improved by doping with suitable transition metal and through surface reconstruction.

Automated summary

In this study, undoped and cobalt-doped BiPO4 catalysts were successfully synthesized using a one-step glycinenitrate decomposition method. The results showed that BiPO4 undergoes surface reconstruction during the oxygen evolution reaction (OER) and is converted into Bi2O3, which acts as the active catalyst for OER. The 5% cobalt-doped BiPO4 exhibited excellent OER activity with low overpotentials of 328 mV and 394 mV for current densities of 10 and 50 mA cm(-2), respectively, which were much lower than that of undoped BiPO4 (480 mV). Furthermore, the polarization curves of the 5% cobalt-doped BiPO4 showed negligible changes in overpotential even after 20 hours of continuous electrolysis, demonstrating excellent stability in alkaline KOH. This work highlights the enhancement of the intrinsic electro-catalytic activity of phosphate-based catalysts by doping with suitable transition metals and through surface reconstruction.