FeP/MoS₂ Enriched with Dense Catalytic Sites and High Electrical Conductivity for the Hydrogen Evolution Reaction

Among sulfide-based electrocatalysts for the hydrogen evolution reaction (HER), molybdenum disulfide (MoS₂) remains at the forefront. However, the HER performance is undermined by high electrical resistance and, due to inherent stacking of MoS₂ layers, low density of accessible functional sites. Herein, an effective synergy between 2D MoS₂ ultrathin nanosheets and iron monophosphide (FeP) nanoparticles is demonstrated, which produces electrocatalyst (FeP/MoS₂) endowed with substantially higher electrical conductivity as well as number of active sites. The as-prepared FeP/MoS₂ exhibits remarkable performance for HER; requires significantly low overpotential (110 mV) as compared to MoS₂ (265 mV) and FeP (210 mV) to generate benchmark 10 mA cm^-2. Furthermore, the performance of as-prepared electrode is notably higher than that of FeP dispersed on carbon; FeP/C requires 138 mV to produce 10 mA cm^-2. Crucial properties of the electrodes - FeP, MoS₂, FeP/MoS₂, and FeP/carbon - such as surface areas, intrinsic electrical conductivity, surface charge transfer resistance, catalytic active centers, and turnover frequency are investigated, and correlated to the performance. Findings reveal that the density of catalytic sites is predominant among electrode's performance-dictating features. In addition, the DFT calculations show that the FeP cluster loaded on MoS₂ nanosheet can effectively promote the HER kinetics. The study highlights the utilization of thin nanosheets of active sites (e.g., MoS₂) as a robust support for the secondary catalytic centers in electrochemical energy conversion applications.