Syngas Conversion to C2 Species over WC and M/WC (M = Cu or Rh) Catalysts: Identifying the Function of Surface Termination and Supported Metal Type.

Abstract

Improving the selectivity and activity of C2 species from syngas is still a challenge. In this work, catalysts with monolayer Cu or Rh supported over WC with different surface terminations (M/WC (M = Cu or Rh)) are rationally designed to facilitate C2 species generation. The complete reaction network is analyzed by DFT calculations. Microkinetics modeling is utilized to consider the experimental reaction temperature, pressure, and the coverage of the species. The thermal stabilities of the M/WC (M = Cu or Rh) catalysts are confirmed by AIMD simulations. The results show that the surface termination and supported metal types in the M/WC (M = Cu or Rh) catalysts can alter the existence form of abundant CHx (x = 1-3) monomer, as well as the activity and selectivity of CHx monomer and C2 species. Among these, only the Cu/WC-C catalyst is screened out to achieve outstanding activity and selectivity for C2H2 generation, attributing to that the synergistic effect of the subsurface C atoms and the surface monolayer Cu atoms presents the noble-metal-like character to promote the generation of CHx and C2 species. This work demonstrates a new possibility for rational construction of other catalysts with the non-noble metal supported by the metal carbide, adjusting the surface termination of metal carbide and the supported metal types can present the noble-metal-like character to tune catalytic performance of C2 species from syngas.