Pronounced effect of phosphidization on the performance of CoOx encapsulated N-doped carbon nanotubes towards oxygen evolution reaction

Research on water splitting reaction is on priority to explore an alternative source of energy with little to no carbon emissions. Among the two half reactions of electrochemical water splitting, oxygen evolution reaction (OER) is highly desirable yet challenging to prepare a cost effective and viable electrocatalyst to boost the OER activity. Herein, we have prepared a novel electrocatalyst, CoOx-CoP/N-CNTs, by the phosphidization of cobalt oxides (CoOx) encapsulated N- doped carbon nanotubes (CoOx/N-CNTs). The CoOx/N-CNTs composite is derived via pyrolysis of cobalt based zeolitic imidazole framework (ZIF-12) at 950 °C under argon atmosphere. The CoOx/N-CNTs is phosphidized at various temperatures ranging from 320 °C to 400 °C. The optimized temperature to attain the best catalytic activity is 380 °C. The phosphatized material, CoOx-CoP/N-CNTs, shows superior performance towards OER with an overpotential of 250 mV @ 20 mAcm−2 vs 532 mV @ 20 mAcm−2 of un-phosphidized material, CoOx/N-CNTs, which shows significant effect of phosphidization. The maximum current density of 160 mAcm−2 in 1 M KOH solution is achieved.