Boosting hydrogen production via alkaline water splitting: Impact of Ag doping in Gd₂O₃ nanosheet arrays

Hydrogen is a preferable renewable energy carrier in decarbonization efforts to develop sustainable and carbon-free economies due to its high energy density and absence of pollutant emissions during combustion. Among others, electrochemical water splitting (EWS) is a sustainable and eco-friendly technology for producing green hydrogen, representing an essential initial step towards achieving carbon neutrality. In this study, we synthesized a bifunctional electrocatalyst by vertically anchoring Ag-doped Gd₂O₃ nanosheet arrays onto a three-dimensional nickel foam (NF) substrate. The developed materials were thoroughly investigated using various analytical techniques. Furthermore, the electrocatalyst effectively performed oxygen evolution reactions (OER) and hydrogen evolution reactions (HER). The Ag_4%-Gd₂O₃/NF exhibited boosted HER activity, achieving higher current densities ranging from 10 to 400 mA cm⁻² at an overpotential between 14 and 122 mV. This study also highlights the considerable impact of metal sites in both Ag_4%-Gd₂O₃/NF and Gd₂O₃/NF on the HER catalytic process. Similarly, the Ag_4%-Gd₂O₃ electrocatalyst exhibited superior OER activity, with an overpotential of 209 mV at 10 mA cm⁻². The optimized composition also shows Tafel slope of 25 and 20 mVdec⁻¹. Furthermore, Ag_4%-Gd₂O₃ demonstrated the ability to generate oxygen gas bubbles in approximately 20 h for OER, making it an attractive material for energy conversion and storage devices.