Interfacial engineering of transition-metal sulfides heterostructures with built-in electric-field effects for enhanced oxygen evolution reaction

Developing highly efficient, durable, and non-noble electrocatalysts for the sluggish anodic oxygen evolution reaction (OER) is the pivotal for meeting the practical demand in water splitting. However, the current transition-metal electrocatalysts still suffer from low activity and durability on account of poor interfacial reaction kinetics. In this work, a facile solid-state synthesis strategy is developed to construct transition-metal sulfides heterostructures (denoted as MS₂/NiS₂, M = Mo or W) for boosting OER electrocatalysis. As a result, MoS₂/NiS₂ and WS₂/NiS₂ show lower overpotentials of 300 mV and 320 mV to achieve the current density of 10 mA·cm⁻², and smaller Tafel slopes of 60 mV·dec⁻¹ and 83 mV·dec⁻¹ in 1 mol·L⁻¹ KOH, respectively, in comparison with the single MoS₂, WS₂, NiS₂, as well as even the benchmark RuO₂. The experiments reveal that the designed heterostructures have strong electronic interactions and spontaneously develop a built-in electric field at the heterointerface with uneven charge distribution based on the difference of band structures, which promote interfacial charge transfer, improve absorptivity of OH⁻, and modulate the energy level more comparable to the OER. Thus, the designed transition-metal sulfides heterostructures exhibit a remarkably high electrocatalytic activity for OER. This study provides a simple strategy to manipulate the heterostructure interface via an energy level engineering method for OER and can be extended to fabricate other heterostructures for various energy-related applications.