A New Class of Zn1-xFex-Oxyselenide and Zn1-xFex-LDH Nanostructured Material with Remarkable Bifunctional Oxygen and Hydrogen Evolution Electrocatalytic Activities for Overall Water Splitting

The scalable and cost-effective H-2 fuel production via electrolysis demands an efficient earth-abundant oxygen and hydrogen evolution reaction (OER, and HER, respectively) catalysts. In this work, for the first time, the synthesis of a sheet-like Zn1-xFex-oxyselenide and Zn1-xFex-LDH on Ni-foam is reported. The hydrothermally synthesized Zn1-xFex-LDH/Ni-foam is successfully converted into Zn1-xFex-oxyselenide/Ni-foam through an ethylene glycol-assisted solvothermal method. The anionic regulation of electrocatalysts modulates the electronic properties, and thereby augments the electrocatalytic activities. The as-prepared Zn1-xFex-LDH/Ni-foam shows very low OER and HER overpotentials of 263 mV at a current density of 20 mA cm(-2) and 221 mV at 10 mA cm(-2), respectively. Interestingly, this OER overpotential is decreased to 256 mV after selenization and the HER overpotential of Zn1-xFex-oxyselenide/Ni-foam is decreased from 238 to 202 mV at 10 mA cm(-2) after a stability test. Thus, the Zn1-xFex-oxyselenide/Ni-foam shows superior bifunctional catalytic activities and excellent durability at a very high current density of 50 mA cm(-2). More importantly, when the Zn1-xFex-oxyselenide/Ni-foam is used as the anode and cathode in an electrolyzer for overall water splitting, Zn1-xFex-oxyselenide/Ni-foam(+)& Zn1-xFex-oxyselenide/Ni-foam(-) shows an appealing potential of 1.62 V at 10 mA cm(-2). The anionic doping/substitution methodology is new and serves as an effective strategy to develop highly efficient bifunctional electrocatalysts.