Modulation of oxygen vacancies influences the electrocatalytic performance of Ni-doped ceria for oxygen and hydrogen evolution

Abstract

The development of high-performance catalysts for electrochemical water splitting continues to drive advancements in sustainable hydrogen production. With ceria-based materials being potential catalysts owing to their remarkable redox behaviour, modulation of defects in ceria is an effective strategy for efficient electrocatalytic water splitting. Thus, aiming to study the creation of oxygen vacancies as a function of dopant concentration, this report demonstrates enhanced electrocatalytic water splitting by regulating defects in ceria via nickel doping. Nickel-doped ceria acts as a bifunctional electrocatalyst with enhanced activity for both oxygen and hydrogen evolution. This improvement stems from interfacial interactions between Ni and the CeO₂, which enhances oxygen vacancy defects in ceria. Mechanistic insights derived by a range of spectroscopic techniques reveal an enhancement in oxygen vacancies in ceria with the increase in the concentration of the dopant. Photoluminescence (PL) studies reveal suppressed charge recombination, indicating efficient electron–hole separation facilitated by the defects. The defect regulated electrocatalytic performance has been established via the electrocatalytic hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) with the evolution of H₂ and O₂ quantitatively estimated, using Ni-doped CeO₂ and undoped CeO₂. Notably, doping of Ni results in a significant reduction in overpotential by 87 mV for oxygen evolution and 59 mV for hydrogen evolution. In addition, current densities also experience a substantial increase by 166 mA cm⁻² for oxygen evolution and 96 mA cm⁻² for hydrogen evolution. The reduction in the Tafel slope from 381 to 199 mV dec⁻¹ for the OER and from 334 to 217 mV dec⁻¹ for the HER indicates faster reaction kinetics. Chronoamperometric measurement reveals notable electrochemical stability of the Ni-doped CeO₂ electrocatalyst. This study on defect structure-related electrocatalysis provides insight into the dopant regulated defect generation in ceria-based materials for designing electrocatalysts for effective water splitting.