Amorphous NiO_n coupled with trace PtO_x toward superior electrocatalytic overall water splitting in alkaline seawater media

Developing corrosion resistance bifunctional electrocatalysts with high activity and stability toward both hydrogen evolution reaction (HER) and oxygen evolution reaction (OER), especially electrolysis in seawater, is of prime significance but still pressingly challenging. Herein, in-situ introduced PtO_x on the derivative amorphous NiO_n is prepared via heat treatment of Ni ZIF-L nanosheets on nickel foam under low temperature (PtO_x-NiO_n/NF). The synthesized PtO_x-NiO_n/NF possesses suprahydrophilic and aerophilic surface, and then in favor of intimate contact between the electrode and electrolyte and release of the generated gas bubbles during the electrocatalysis. As a result, the in-situ PtO_x-NiO_n/NF electrode presents outstanding bifunctional activity, which only requires extremely low overpotentials of 32 and 240 mV to reach a current density of 10 mA·cm^–2 for HER and OER, respectively, which exceeds most of the electrocatalysts previously developed and even suppresses commercial Pt/C and RuO₂ electrodes. As for two-electrode cell organized by PtO_x-NiO_n/NF, the voltages down to 1.57 and 1.58 V are necessary to drive 10 mA·cm^–2 with remarkable durability in 1 M KOH and alkaline seawater, respectively, along with remarkable stability. Moreover, a low cell voltage of 1.88 V is needed to achieve 1,000 mA·cm^–2 toward water-splitting under industrial conditions. This study provides a new idea for designing in-situ amorphous metal oxide bifunctional electrocatalyst with strong Pt–support interaction for overall water splitting.