N-doped graphene quantum dots as charge-transfer-bridge at LaSrCoO/MoSe₂ heterointerfaces for enhanced water splitting

A bifunctional electrocatalyst interface requires superior charge transfer and good electrical conductivity to produce a water splitting reaction that is overall efficient and stable. In the context of engineering the interfacial band alignment, we demonstrate a novel and straightforward approach to control the electrochemical activity of the bifunctional catalysts with precision by bridging conductive N-doped graphene quantum dots (N-GQDs, 2–3 nm) between La_0.5Sr_0.5CoO_3–δ (LSC) and MoSe₂ interfaces. The N-GQDs govern the charge transfer process at the interface, exhibiting higher Co³⁺ cations and metallic 1 T-MoSe₂ phase-transition compared to those of LSC and LSC-MoSe₂ composites. As a result, the optimized LSC-N-GQDs-MoSe₂ electrocatalyst possessed a lower overpotential, Tafel slope, and charge transfer resistance in HER and OER than pure and LSC-MoSe₂ electrocatalysts in an alkaline solution. The Tafel slopes (64 mV·dec⁻¹ and 51 mV·dec⁻¹ for HER and OER respectively) are smaller than those of current solutions that are commercially available, showing a higher performance at a high current density of 500 mA·cm⁻² with a long-term 24 h stability test. The key design of the current study is based on conductive bridging in the bifunctional catalyst to improve the interfacial charge transfer and electrochemical reaction.