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For the first time, a mayenite based material combining calcium and copper (18.0/37.6/44.4 estimated active wt % CaO/CuO/Ca 12 Al 14 O 33 , CuO/CaO = 2.1 [wt/wt]) has been subjected to three full calcium−copper chemical looping combustion (Ca−Cu Looping) cycles in a fixed bed reactor (70.0 g of combined material and 3.5 g of 18.0 wt % Ni/Al 2 O 3 reforming catalyst), demonstrating the feasibility of a combined materials approach to hydrogen production through Ca−Cu Looping. Combined materials were characterized by helium pycnometry, mercury intrusion, nitrogen adsorption, X-ray diffraction, thermogravimetric analysis, scanning electron microscopy, and energy dispersive X-ray diffraction before and after reactor testing. A carbon dioxide capture capacity of 14.6−15.0 g CO 2 /100 g (640−660 °C, 1.0 MPa, 2.5 kg CH 4 kg cat −1 h −1 ), full oxidation, and expected calcination efficiencies (51−64%) were obtained. Combined material performance is comparable to that of segregated materials previously tested in the same experimental rig. Process intensification of Ca−Cu Looping through combined materials development is promising. more widespread implementation and acceptance in the 49 industrial sector. 4 50 The topic of the presented work is hydrogen production 51 from natural gas with CCS, i.e., CO 2 capture from a stationary 52 point-source within the chemical industry. The annual global 53 production of hydrogen is approximately 65 Mt/year where 54 95% is produced from fossil fuels (48% from reforming of 55 natural gas) and the majority of hydrogen is "used where it's 56 produced" in refinery feedstock hydrotreatment or in the 57 production of miscellaneous commodity chemicals (ammonia, 58 methanol, etc.). 5,6 The associated CO 2 emissions for a large-59 scale, hydrogen producing natural gas reforming plant are 60 estimated to be in the order of 7.0−8.1 tCO 2 /tH 2 . 7,8 As an 61

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