Synthesis of highly effective stabilized CaO sorbents via a sacrificial N-doped carbon nanosheet template

Calcium looping, a promising high-temperature CO2 capture technique, offers a mid-term economic solution to mitigate anthropogenic CO2 emissions. The main challenge in calcium looping is the synthesis of highly efficient CaO-based sorbents that can be used over many reaction cycles. Here, a sacrificial N-doped carbon nanosheet template was developed which produces MgO-stabilized CaO sorbents with fast adsorption rates, high capacities and remarkable long-term performance over many cycles. The characterization results show that such a template was formed through in situ pyrolysis of an organic acid and nitrates in a simple heating process in nitrogen. The presence of a carbonaceous template prevented crystallite growth, featured highly macroporous nanosheet (approximate to 60 nm thick) morphologies, and ensured homogeneous mixing of Ca and Mg, which are essential to minimize diffusion limitations, mitigate sintering, and provide structural stability. Thus, 10 mol% MgO acting as an inert stabilizer was sufficient to achieve a CO2 uptake of 0.65 g g(-1) (corresponding to a capacity retention of 89.9%) after 10 cycles under realistic conditions, as confirmed by TGA analysis. This N-doped carbon template can be applied generally to produce a wide range of porous and nanostructured stabilized CaO sorbents with stable CO2 uptake.