Misfit-layered Bi_1.85Sr₂Co_1.85O_7.7-δ for the hydrogen evolution reaction: Beyond van der Waals heterostructures

Recent research on stable 2D nanomaterials has led to the discovery of new materials for energy-conversion and energy-storage applications. A class of layered heterostructures known as misfit-layered chalcogenides consists of well-defined atomic layers and has previously been applied as thermoelectric materials for use as high-temperature thermoelectric batteries. The performance of such misfit-layered chalcogenides in electrochemical applications, specifically the hydrogen evolution reaction, is currently unexplored. Herein, a misfit-layered chalcogenide consisting of CoO₂ layers interleaved with an SrO-BiO-BiO-SrO rock-salt block and having the formula Bi_1.85Sr₂Co_1.85O_7.7-δ is synthesized and examined for its structural and electrochemical properties. The hydrogen-evolution performance of misfit-layered Bi_1.85Sr₂Co_1.85O_7.7-δ, which has an overpotential of 589 mV and a Tafel slope of 51 mV per decade, demonstrates the promising potential of misfit-layered chalcogenides as electrocatalysts instead of classical carbon.