Tuning transition metal carbide activity by surface metal alloying: a case study on CO₂capture and activation

Abstract

CO2 is one of the main actors in the greenhouse effect and its removal from the atmosphere is becoming an urgent need. Thus, CO2 capture and storage (CCS) and CO2 capture and usage (CCU) are intensively investigated technologies to decrease the concentration of atmospheric CO2. Both CCS and CCU require appropriate materials to adsorb/release and adsorb/activate CO2, respectively. Recently, it has been theoretically and experimentally shown that transition metal carbides (TMC) are able to capture, store, and activate CO2. To further improve the adsorption capacity of these materials, a deep understanding of the atomic level processes involved is essential. In the present work, we theoretically investigate the possible effects of surface metal doping of these TMCs by taking TiC as a textbook case and Cr, Hf, Mo, Nb, Ta, V, W, and Zr as dopants. Using periodic slab models with large supercells and state-of-the-art density functional theory based calculations we show that CO2 adsorption is enhanced by doping with metals down a group but worsened along the d series. Adsorption sites, dispersion and coverage appear to play a minor, secondary constant effect. The dopant-induced adsorption enhancement is highly biased by the charge rearrangement at the surface. In all cases, CO2 activation is found but doping can shift the desorption temperature by up to 135 K.

Assessing the Activity of Ni Clusters Supported on TiC(001) toward CO2 and H2 Dissociation

“…21 Interestingly, the topmost hollow site of Ni 13 /TiC does not adsorb CO 2 nor H 2 , as this site closely resembles the fourfold hollow site of the Ni(100) surface that is known to interact poorly with CO 2 , but it can interact significantly with H 2 . 54 To have a better perspective of the different interactions involved in the H 2 and CO 2 adsorption with the different Ni n clusters supported on TiC, it is interesting to compare with other studies of similar systems either involving TiC(001) surfaces doped with metals, 51,52 other supported metals on TiC(001), 20,55,56 or even other low Miller index Ni surfaces. 57,58 A comparison with these previous works shows that Ni n /TiC(001) systems are really attractive as they interact stronger with H 2 and CO 2 .…”

Atomistic and electronic structure of metal clusters supported on transition metal carbides: implications for catalysis

“…For a discussion on how the cluster size can affect these properties, the reader is referred to the work by Lozano-Reis et al 18 Moreover, it is worth pointing out that another interesting approach to tune the catalytic activity of TMCs is by transition metal doping. Interestingly, López et al 45,46 used DFT calculations to show that doping TiC(001) with other elements can modify its interaction with CO 2 . However, there are no experimental studies on these systems yet, and the number of elements that can be used as dopants is limited.…”

Concepts, models, and methods in computational heterogeneous catalysis illustrated throughCO2conversion

“…These special sites have been predicted to tune the CO 2 capturing capabilities while maintaining the CO 2 activated mode. 230,231 Although practical realization of this idea remains to be done, although such a strategy has been used to improve the electrochemical reduction of CO 2 toward CH 4 on TiC and TiN surfaces. 232 Another way of fine-tuning catalytic active centers toward CO 2 is the generation of surface vacancies.…”