Steam reforming on transition-metal carbides from density-functional theory

TL;DR

This study uses density-functional theory to evaluate the reactivity of various transition-metal carbides for steam reforming, identifying promising catalytic surfaces and highlighting the potential for reactivity tuning.

Contribution

It provides a systematic DFT screening of TMC surfaces for steam reforming, identifying promising catalysts and demonstrating the tunability of reactivity in carbides.

Findings

Delta-MoC(100) surface is highly reactive.

Oxygen-passivated alpha-Mo_2C(100) shows promising catalytic activity.

Carbides exhibit a wide range of reactivities, from inert to too reactive.

Abstract

A screening study of the steam reforming reaction (CH_4 + H_2O -> CO + 3H_2) on early transition-metal carbides (TMC's) is performed by means of density-functional theory calculations. The set of considered surfaces includes the alpha-Mo_2C(100) surfaces, the low-index (111) and (100) surfaces of TiC, VC, and delta-MoC, and the oxygenated alpha-Mo_2C(100) and TMC(111) surfaces. It is found that carbides provide a wide spectrum of reactivities towards the steam reforming reaction, from too reactive via suitable to too inert. The reactivity is discussed in terms of the electronic structure of the clean surfaces. Two surfaces, the delta-MoC(100) and the oxygen passivated alpha-Mo_2C(100) surfaces, are identified as promising steam reforming catalysts. These findings suggest that carbides provide a playground for reactivity tuning, comparable to the one for pure metals.