Heteroatom doping strategy to construct hierarchical 3D/2D P-CoSe₂/Ti₃C₂T_x reinforced Mott-Schottky barrier for...

Heterojunction catalysts are promising materials for energy conversion; however, their charge-transfer efficiency is often hindered by unstable interfacial driving forces and ill-defined charge-transport pathways. To overcome these limitations, precise interfacial engineering is required to promote efficient electron migration. In this study, we constructed an advanced P-CoSe₂/Ti₃C₂T_x heterojunction catalyst via the dual modification of CoSe₂ nanospheres by integrating heterostructure engineering with heteroatom doping. The 3D CoSe₂ nanospheres were anchored onto 2D Ti₃C₂T_x MXene nanosheets, creating a 3D/2D architecture that enlarged the electrochemically active surface area, enhanced interfacial coupling, and shortened charge migration distances. A Mott-Schottky barrier was formed at the CoSe₂/Ti₃C₂T_x interface, facilitating interfacial charge transfer. Heteroatom doping optimized the height of the Schottky barrier and strengthened the built-in electric field, further accelerating electron transport. Thus, P-CoSe₂/Ti₃C₂T_x exhibited remarkable electrocatalytic activity for both the hydrogen evolution reaction (HER) and iodine reduction reaction (IRR). A low overpotential of 116 mV at 10 mA cm^-2 with a Tafel slope of 60 mV dec^-1 for the HER was achieved in 1.0 M KOH. When used as an IRR catalyst in photovoltaic devices, it delivered a power conversion efficiency of 8.80%. Both experimental and density functional theory calculations verified that the built-in electric field could be enhanced by engineering the Schottky barrier height, thereby enabling the rational design of high-performance Mott-Schottky heterojunction catalysts for advanced energy conversion.