Strontium Germanate Nanofibers via Cobalt Intercalation for High-Performance Bifunctional Water Splitting with...

Electrocatalytic water splitting is widely regarded as an effective strategy for the production of clean hydrogen energy. Herein, a series of novel composite bifunctional electrocatalysts (Cox-SGO@CP), with exceptional electrocatalytic performance and promising industrial application, were fabricated via a hydrothermal-electrochemical cobalt intercalation two-step strategy to construct Co-SGO nanowire arrays on carbon paper conductive substrates. Among them, Co40-SGO@CP, recognized as the most effective electrocatalyst, featured uniformly dispersed cobalt within the strontium germanate nanofiber framework, thereby providing abundant accessible active sites. Consequently, it delivered a large electrochemically active surface area and superior catalytic activity for both the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). At a current density of 100 mA·cm^-2, the overpotentials required for the HER and OER were 270.3 and 271 mV, respectively. The corresponding Tafel slopes in the stable LSV region were 69.3 mV·dec^-1 for HER and 41.6 mV·dec^-1 for OER. Both HER and OER processes exhibited stable operation across a broad current density range of 10-100 mA·cm^-2. Notably, a cell voltage of only 1.77 V was sufficient to drive overall water splitting at 100 mA·cm^-2. The Co40-SGO@CP electrode maintained robust structural and compositional stability after durability testing. Moreover, under simulated industrial conditions in 6 M KOH at 70 °C, the Co40-SGO@CP electrode sustained stable catalytic operation for up to 1000 h. Density functional theory (DFT) calculations demonstrated that cobalt incorporation into the SGO lattice induced significant charge transfer with neighboring atoms, thereby modulating the density of states and band structure relative to pristine SGO. By replacing Ge and Sr as the dominant active sites, cobalt centers optimized the free-energy profiles of the elementary steps in both the HER and OER, accounting for the enhanced electrocatalytic performance of Co40-SGO@CP.