RESUMO
CO2 capture, utilization, and storage are promising strategies to solving the problems of superfluous CO2 or energy shortage. Here, mechanochemical reduction of CO2 by a MgH2/CaH2 mixture was first performed, by which we achieve selective methanation of CO2 and acquire an effective CaO-based CO2 sorbent, simultaneously. The selectivity of methanation is near 100% and the yield of CH4 reaches 30%. Four MgO and carbon-doped CaO-based CO2 sorbents (MgO/CaO/C, MgO/2CaO/C, MgO/4CaO/C, and MgO/8CaO/C) were formed as solid products in these reactions. Among them, the MgO/4CaO/C sorbent shows high initial adsorption amount of 59.3 wt% and low average activity loss of 1.6% after 30 cycles. This work provides a novel, well-scalable, and sustainable approach to prepare an efficient inert additive-including CaO-based CO2 sorbent and selectively convert CO2 to CH4 at the same time.
RESUMO
The eCO2RR activity is correlated to the internal structural character of the catalyst. We employed two types of structural models of porphyrin-based MOFs of PCN-222(Cu) and PCN-224(Cu) into heterogeneous catalysis to illustrate the effect of structural factors on the eCO2RR performance. The composite catalyst PCN-222(Cu)/C displays better activity and selectivity (η = 450 mV, FEHCOOH = 44.3%, j = 3.2 mA cm-2) than PCN-224(Cu)/C (η = 450 mV, FEHCOOH = 34.1%, j = 2.4 mA cm-2) for the CO2 reduction to HCOOH in the range of -0.7--0.9 V (vs. RHE) due to its higher BET surface area, CO2 uptake, and a larger pore diameter. It is interesting that PCN-224(Cu)/C displays better performance in the range of -0.4--0.6 V (vs. RHE) due to its greater heat of adsorption, Qst and a higher affinity for CO2 molecule, which could promote the capture of CO2 onto the exposed active sites. As a result, PCN-224(Cu)/C exhibits better stability for the long-term electrolysis.