Design principles of two-dimentional transition metal carbides based CO2RR catalysts

The sustainable and clean technologies for converting CO₂ into value added chemicals was in great demand due to the catastrophic environmental consequences caused by the extraordinary increase of atmospheric CO₂. Two-dimentional transition metal carbides and nitrides (MXenes) are promising candidates in catalytic applications benefited from the similar catalytic property with precious metal and the unique two-dimentional structure. However, it was still crucial to design MXenes based CO₂RR catalysts with satisfying catalytic performance due to the complicated competing between HER and CO₂RR. In this study, the design principle of MXenes for CO₂RR was proposed and discussed comprehensively. The premise that the ideal M₃C₂O₂ structure should have high ΔG(*H) for fabricating efficient MXenes based CO₂RR catalysts was proposed based on the findings on the misleading superior CO₂RR performance over Ti₃C₂O₂_Ov. Furthermore, the adsorption behavior of key reaction intermediates together with the charge transfer between adsorbate and catalysts were investigated over Ta₃C₂O₂ MXenes substituted by a series of late transition metal. With increasing the amount of substituted metals, different metal displayed different trend in catalyzing CO₂RR and HER. Moreover, once the Ti or Ta vacancy was formed, HER was more favored than CO₂RR, which required the gentle method for synthesizing MXenes based CO₂RR catalysts. The proposed designing principles and trends obtained in this study can be applied in guiding the theoretical design and experimental fabrication of efficient MXenes based CO₂RR catalysts.