Single Site Substitution in 2D Molybdenum Carbide: Applications in Electrocatalysis

Two-dimensional carbides and nitrides (MXenes) represent an excellent platform for the fundamental catalysis studies due to their well-defined and tunable structure and theoretically predicted high activity in numerous catalytic reactions. 1 However, the scope of metals capable of forming thermodynamically stable MXenes is limited mostly to early transition metals, making the investigation of properties inherent to mid or late transition metal carbides/nitrides challenging. Here, we present the synthesis and structural characterization of the Mo 2 C T x :M phases (M = Co, Fe; T x = O, OH, F surface terminations), where M substituents occupy molybdenum positions in the Mo 2 C T x lattice, providing isolated Co/Fe sites. Our experimental and DFT studies demonstrate that metal M substitution renders Mo 2 C T x :M carbides active catalysts for the hydrogen evolution reaction. Overall, our work expands the compositional space of the MXene family by introducing materials with isolated metal sites incorporated into the matrix of Mo 2 C T x . The results discussed here highlight the general applicability of the developed synthetic approach and illustrate that tailoring the properties of MXenes for a specific application can be achieved via targeted substitution of the host metal. (1) Anasori, B.; Lukatskaya, M. R.; Gogotsi, Y., Nat. Rev. Mater. 2017, 2 , 16098.