Surface Carbon Formation and its Impact on Methane Dry Reforming Kinetics on Rhodium-Based Catalysts by Operando...

A mechanism for carbon deposition and its impact on the reaction kinetics of Methane Dry Reforming (MDR) using Rhodium-based catalysts is presented. By integrating Raman spectroscopy with kinetic analysis in an operando-annular chemical reactor under strict chemical conditions, we discovered that carbon deposition on a Rh/α-Al₂O₃ catalyst follows a nucleation-growth mechanism. The dynamics of carbon aggregates at the surface is found to be ruled by the CO₂/CH₄ ratio and the inlet CH₄ concentration. The findings elucidate the spatiotemporal development of carbon aggregates on the catalyst surface and their effects on catalytic performance. Furthermore, the proposed mechanism for carbon formation shows that the influence of CO₂ on MDR kinetics is an indirect result of carbon accumulation over time frames exceeding the turnover frequency, thus reconciling conflicting reports in the literature regarding CO₂'s kinetic role in MDR.