Increasing CO2 emissions worldwide and their negative impact on climate change has led to a notable academic and industrial interest in the conversion of CO2 to fuels and value-added products. Dry reforming of methane (DRM; CH4(g) + CO2(g) → CO(g) + H2(g)) reaction is a promising route for CO2utilization. Ni-based catalysts are widely employed for this reaction. However, these are less active and are prone to deactivation due to carbon deposition. CO2 dry reforming reaction mechanism is widely debated in the literature and gaining mechanistic insights is pivotal in developing more active and coke resistant catalysts based on a bottom-up approach. For DRM reaction, the deactivation of Ni-based catalyst is a key challenge, and this impedes commercializing the DRM process. Doping boron at the sub-surface interstitial sites in Ni prevents the diffusion of carbon. Hence, I investigated NiB as a potential catalyst. Electronic structure calculations within the framework of DFT were performed using the Vienna ab initio simulation package (VASP). The effect of doping was evaluated by analyzing the reaction mechanisms on NiB and compared with that on Ni (111). The dominant reaction pathway was CO2*→CO*+O*; CH4→CH3*→CH2*→C*→CO* and CO2*→CO*+O*; CH4→CH3*→CH2*→CH2O*→CHO*→CO* on Ni (111) and NiB surfaces respectively. I revealed that boron doping alters the dominant reaction pathway (via CH2* oxidation route) to kinetically hinder carbon formation (no C* intermediate). In contrast to Ni, the barriers in CH4 activation routes and Boudouard reaction were significantly lower on NiB, but the CO2 activation barrier (124 kJ/mol) was high resulting in reduced conversion. Hence, the resistance towards deactivation was achieved at the cost of reduced reactant conversion.

The strategy was to reduce the CO2 activation barrier selectively to improve the activity of NiB without compromising the stability. Single-atom alloys (SAA) are very promising for selective catalysis and hence a computational screening was performed to identify thermodynamically stable NiB-based SAA that selectively reduces the CO2 activation barrier. The thermodynamic stability was evaluated against clustering and Mn-NiB SAA was identified as the only candidate on which there was a significant reduction in the CO2 activation barrier (68 kJ/mol). Subsequently, DRM reaction was studied on Mn-NiB SAA. Mn-NiB SAA has a significantly lower barrier for CH4 (compared to Ni) and CO2 (compared to NiB) activation. Additionally, the high endergonicity for CH4 stepwise dehydrogenation to form C* combined with a low barrier for Boudouard reaction prevents the catalyst deactivation. The gained insights from SAA would serve as guidelines for the development/synthesis of alloy catalysts that can prevent carbon deposition without compromising the catalytic activity.

Methane pyrolysis (CH4 (g)→C*(s)+H2 (g)) is a promising reaction for hydrogen generation without producing carbon dioxide. For reasonable conversion, a catalyst must be employed for this reaction. However, conventional solid catalysts are prone to deactivation due to carbon produced in the reaction. Interestingly, performing the reaction in a molten media would allow the carbon to float on the surface of the melt resulting in easy carbon removal. My study focuses on understanding the methane pyrolysis reaction in metal dispersed salt melt. To study the metal-salt system, quantum mechanical molecular dynamics simulations are performed using Car-Parrinello Molecular Dynamics (CPMD). The consequence of carbon diffusion in metal will be studied and catalyst modifications will be proposed.