Intermolecular Metallic Single-Site Complexes Dispersed on Mo₂TiC₂T_x/MoS₂ Heterostructure Induce Boosted Solar-Driven Water Splitting

Successful development of an electrocatalyst capable to promote the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER) elements of water electrolysis is desirable for green hydrogen gas production. Herein, this work designs intermolecular metallic single-site complexes of iron phthalocyanine (Fe_Pc) and vanadium oxide phthalocyanine (VO_Pc) dually immobilized on 3D hierarchical MoS₂-coated MXene Mo₂TiC₂T_x (MX/MoS₂) heterostructures as a high-performance bifunctional electrocatalyst. The well-organized structure with an unusual coordination environment and electronic localization impressively enhances water adsorption and activation to remarkably accelerate HER and OER kinetics. Therefore, the hybrid material requires overpotentials as small as 17.4 and 300 mV to drive 10 mA cm⁻² for the HER and 50 mA cm⁻² for the OER in 1.0 m KOH media, respectively. The electrolyzer of MX/MoS₂-Fe_PcVO_Pc(+,−) exhibits low cell voltage of only 1.45 V to reach a current response of 10 mA cm⁻² in 7.0 m KOH at 75 °C along with excellent current retention stability of 99%/94% after long-term operations of 30 h at 10/50 mA cm⁻². Moreover, a solar-to-hydrogen conversion efficacy of 19.96% is achieved in a solar energy-powered water electrolysis system, highlighting the great potential of the developed MX/MoS₂-Fe_PcVO_Pc electrocatalyst toward water electrolysis.