We report the discovery of a new class of oxides – poly-cation oxides (PCOs) – that consist of multiple cations and can thermochemically split water in a two-step cycle to produce hydrogen (H2) and oxygen (O2).
Dissociation of CO2 to form CO can play a key role in decarbonizing our energy system. Fe-poor ferrites exhibit significantly higher capacity for thermochemical CO2 dissociation than state-of-the-art materials such as ceria and perovskites.
CO2 utilization via the
reverse water–gas-shift
(RWGS) reaction for the production of CO and then long-chain hydrocarbons
is a potentially scalable method to mitigate rising global CO2 emissions, if appreciable CO yields can be achieved at low
reaction temperatures. Here, we report that Fe0.35Ni0.65O
x
achieves, to the best of
our knowledge, a record high experimentally measured CO yield of 80
mL CO/gMOx
/cycle at low reaction temperatures
(500 °C for both oxidation and reduction steps) in a chemical
looping (CL) process. This reported yield is substantially higher
than previously reported RWGS-CL metal oxides at 500 °C. We identified
the composition of the metal oxide Fe0.35Ni0.65O
x
using the Calculation of Phase Diagrams
(CALPHAD) methodology to screen and filter through many combinations
of metal oxides. We then experimentally tested this Fe0.35Ni0.65O
x
metal oxide for chemical
looping RWGS and utilized X-ray characterization techniques and CALPHAD
to find that a spinel to metallic phase transition gives Fe0.35Ni0.65O
x
its noteworthy CO
yield and oxygen capacity. We emphasize the importance of thermodynamics
calculations and CALPHAD screening to quickly search through the vast
design space of metal oxides to greatly reduce the amount of necessary
experimentation.
Thermochemical looping splitting of water and carbon dioxide (CO2) with greenhouse-gas-free (GHG-free) energy has the potential to help address the Gt-scale GHG emissions challenge. Reaction thermodynamics largely contributes to the...
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