Ultra-fast surface reconstruction enabled by the built-in electric field in heterostructured CoS2/CuS for water electrolysis

Abstract

Transition-metal chalcogenides (TMCs) show great potential as highly efficient and cost-effective electrocatalysts for oxygen evolution reaction (OER). Yet the electrochemical conversion into oxides/hydroxides remains poorly understood. In this work, we develop a built-in, electric-field-induced surface reconstruction strategy for ultra-fast self-activation of transition metal sites in self-supporting CoS 2 /CuS heterostructures. The activated CoS 2 /CuS grown on carbon cloth with oxygenated surface species displays an outstanding OER electrocatalytic activity with ultra-low overpotentials of only 136 mV at the current density of 10 mA cm −2 and 266 mV at 100 mA cm −2 in 1.0 M KOH. Comparative studies via synchrotron radiation X-ray absorption spectroscopy and theoretical calculations are employed to elucidate that the built-in electric field within heterointerfaces significantly promotes the reconstruction efficiency by decreasing the formation energy of (oxy)hydroxide species. We believe this work provides new perspectives to conceive catalysts with ultra-low overpotentials and complements the fundamental comprehension of TMCs’ self-reconstruction mechanism. • The nature of metallic site reconstruction upon OER is revealed via combined XAS and DFT • A simplified reconstruction process enabled by the built-in electric field of CoS 2 /CuS • The self-standing electrode shows practical potential for overall water electrolysis A comprehensive perception of the structural transformation and reconstruction of metallic surface sites upon the OER process is essential for the rational design of high-performance OER catalysts. To simplify the energy-consuming activation process and achieve rapid reconstruction, Man et al. report a built-in electric field strategy for modulating surface dynamics of heterostructured CoS 2 /CuS.