Background: Ceria (CeO2) is an important catalyst component and support/
carrier and high surface area ceria is extremely useful for increasing catalytic
activity in several low temperature applications such as emissions control, water gas
shift (WGS), CO oxidation, and VOC combustion/destruction. The highest surface
areas reported in the literature using aqueous synthetic routes, in the absence of organic
solvents, are in the range of 200–260 m2/g. We report here the preparation of
high surface area ceria using three different synthesis methods: 1) dry decomposition
of common cerium salts as precursors, 2) precipitation, and 3) soft combustion
Methods: The three routes were studied using common and readily available cerium precursors, without
using expensive templates, surfactants, alcoholic solvents, supercritical drying, or high pressure equipment.
We obtained unprecedented high surface areas of >300m2/g by precipitation, after mapping out
vast parameter spaces including Ce salt precursor selection, choice of base, pH, method (precipitation at
constant pH or titration (pH ramp)), temperature, and aging conditions. We screened more than half of
the periodic table and all the rare earth metals from Pr to Lu.
Results: For dry decomposition, BET surface areas of ~170 m2/g were obtained from Ce (III) acetate
and ~135 m2/g from Ce (III) oxalate and Ce (III) carbonate precursors. Using wet combustion synthesis
with aqueous glyoxylic acid and ketoglutaric acid as dispersants we measured ~160 m2/g when starting
from Ce (III) acetate but lower surface areas of ~120 m2/g from Ce (III) nitrate. An unprecedented surface
area of ~300 m2/g was obtained by precipitation of Ce (IV) nitrate with NMe4OH after a multiparameter
optimization using a 64-vessel co-precipitation robotic synthesis station. Supported ceria catalysts
were prepared by impregnation with active metals and found to be highly active for the low temperature
water gas shift reaction, CO oxidation, and VOC combustion.
Conclusion: This work demonstrates the potential to significantly improve conventional inexpensive
synthetic routes to high surface area materials with, in many cases, unprecedented high surface areas, by
using high throughput mapping of multi-dimensional parameter spaces. It provides practical alternatives
to both sol-gel and hydrothermal synthesis methods.