Cu-oxide catalysts have a tendency to deactivate dramatically in reverse water gas shift (RWGS) reaction, because of the aggregation of supported copper particles at high temperatures. Herein, β-Mo2C, which is a typical type of transition-metal carbide, has been demonstrated to be capable of dispersing and stabilizing copper particles. Cu/β-Mo2C catalysts exhibit good catalytic activity and stability for the RWGS reaction. Under relatively high weight hourly space velocity (WHSV = 300 000 mL/g/h), the optimized 1 wt % Cu/β-Mo2C exhibits superior activity over traditional oxide-supported Pt- and Cu-based catalysts. The activity was well-maintained in a 40 h stability test, and the catalyst shows stable reactivity in a six-cycle start-up cool-down experiment. Detailed structure characterizations demonstrate that the strong interaction between Cu and β-Mo2C effectively promotes the dispersion of supported copper and prevents the aggregation of Cu particles, which accounts for the extraordinary activity and stability for the RWGS reaction.

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CO oxidation at room temperature over the Au/CeO2 catalyst was investigated, of which the induction period arising from unreduced cationic Au was disclosed. The effect of humidity in reactant stream on catalyst activity was investigated during induction and deactivation periods. The induction period was significantly reduced from 44.8 min in dry stream to 3.3 min in wet stream containing 0.58 vol % of H2O. The induction period was slightly shortened by further increasing water concentration in the reactant stream. The maximum initial activity was achieved with a wet stream containing 0.74 vol % of H2O vapor. In situ DRIFTS measurements suggested that humidity contributed to the formation and consumption of reaction intermediates [COOH]s and hence enhanced the initial activity. After the induction period, the deactivation phenomena of Au/CeO2 catalyst at varied rates under both wet and dry streams were observed. In contrast to a slow deactivation under dry stream, a fast deactivation in wet stream was first observed due to rapid blockage of active sites by water adsorption, followed by a slow deactivation rate due to gradual formation of surface carbonate species over catalyst with time on stream. A mechanism was proposed to illustrate the existence of induction period under both wet and dry streams.