Gradient heating epitaxial growth gives well lattice-matched Mo${}_2$C-Mo${}_2$N heterointerfaces that boost both electrocatalytic hydrogen evolution and water vapor splitting

An optimized approach to producing lattice-matched heterointerfaces for electrocatalytic hydrogen evolution has not yet been reported. Herein, we present the synthesis of lattice-matched Mo${}_2$C-Mo${}_2$N heterostructures using a gradient heating epitaxial growth method. The well lattice-matched heterointerface of Mo${}_2$C-Mo${}_2$N generates near-zero hydrogen-adsorption free energy and facilitates water dissociation in acid and alkaline media. The lattice-matched Mo${}_2$C-Mo${}_2$N heterostructures have low overpotentials of 73 mV and 80 mV at 10 mA cm${}^{-2}$ in acid and alkaline solutions, respectively, comparable to commercial Pt/C. A novel photothermal-electrocatalytic water vapor splitting device using the lattice-matched Mo${}_2$C-Mo${}_2$N heterostructure as a hydrogen evolution electrocatalyst displays a competitive cell voltage for electrocatalytic water splitting. (© 2022 Wiley‐VCH GmbH)