Tailoring active sites on heterostructures through electrocatalytic engineering for efficient bifunctional production of H₂and H₂O₂

Single-atom catalysts (SACs) are highly attractive for catalytic water splitting due to their ability to maximize the utilization efficiency of metal atoms. In this work, copper single atoms (CuSACs) were heterogeneously anchored onto the MWCNT/FeMOF (CuSACs@MC/FM) catalyst surface through atomic-level dispersion of Cu, effectively tuning the heterogeneity of the catalyst. The existence of CuSACs enhances the number of accessible active sites, enabling efficient hydrogen and oxygen evolution reaction (HER and OER) activity in alkaline media. The CuSACs@MC/FM hybrid catalysts exhibit low overpotentials (OER: 165 mV and HER: 40 mV), small Tafel slope value (OER: 21 mV/dec and HER: 38 mV/dec) and excellent durability of up to 100 h for both OER and HER at 10 mA/cm²in 1 M KOH. Furthermore, we assembled a bifunctional CuSACs@MC/FM hybrid catalyst for overall water splitting and achieved a low cell voltage of 1.54 V at 10 mA/cm²with excellent long-term stability. Additionally, CuSACs@MC/FM delivered a high mass activity of 70 A/g and ∼84 % selectivity for H₂O₂ in the ORR. X-ray absorption spectroscopy revealed a dominant Cu–N coordination peak at ∼1.4 Å, confirming the presence of atomically dispersed Cu–N sites that serve as the active centers and enhance the heterogeneous catalytic activity. This work demonstrates that interfacial site tuning and atomic-level modulation can significantly improve catalyst durability and efficiency, establishing CuSACs@MC/FM as a highly effective electrocatalyst to produce both H₂ and H₂O₂.