A garnet-type solid-state electrolyte Li6.4La3Zr1.4Ta0.6O12 (LLZTO) was modified using dopamine to improve the wettability of LLZTO with PEO, allowing 80 wt% LLZTO to be uniformly dispersed in 20 wt% PEO/LiTFSI polymer electrolyte.
Redox activity has been considered the descriptor of the catalytic performance of transition-metal oxides with the crystal family of ABO 3 perovskites. Although elemental doping is an efficient way to promote their activity for water splitting, most research has been centered only on the influence of doping A/B sites. This work demonstrates that F-anion substitution can make the O p band closer to the Femi level and activate the lattice O forming mobile O*. These features help regulate the lattice O sites in perovskites and thus promote the activity of perovskite oxides for water-splitting reactions.
Shale/tight gas plays an increasingly
important role to meet the
growing global energy demand and reduce carbon emissions. Unlike conventional
reservoirs, shale formations are subject to rock heterogeneity and
have pore size distributions ranging from sub-1 nm to a few micrometers.
Thanks to the large number of nanosized pores, adsorbed methane capacity
plays a dominant role in total shale gas-in-place. Methane adsorption
behaviors can vary drastically in micropores and mesopores, and rock
surface type may also greatly affect its adsorption. In this review,
we provide a systematic discussion on measurements of shale rock properties
including rock compositions and pore structures such as specific surface
area (SSA) and pore size distribution (PSD), which are important parameters
for methane adsorption in shale nanoporous media. We also provide
in-depth discussions on experimental measurements on methane (excess)
adsorption in shale nanoporous media, methane adsorption behavior
characterization based on molecular simulations, and various excess-adsorption-to-absolute-adsorption
conversion methods. We pay particular attention to the assumptions
and working mechanisms proposed in various interpretation methods
which are embedded in pore structures (SSA and PSD) and absolute adsorption
characterizations. In the end, we summarize the key challenges in
the methane adsorption characterization in shale media.
CO2 sequestration in shale reservoirs is an economically
viable option to alleviate carbon emission. Kerogen, a major component
in the organic matter in shale, is associated with a large number
of nanopores, which might be filled with water. However, the CO2 storage mechanism and capacity in water-filled kerogen nanopores
are poorly understood. Therefore, in this work, we use molecular dynamics
simulation to study the effects of kerogen maturity and pore size
on CO2 storage mechanism and capacity in water-filled kerogen
nanopores. Type II kerogen with different degrees of maturity (II-A,
II-B, II-C, and II-D) is chosen, and three pore sizes (1, 2, and 4
nm) are designed. The results show that CO2 storage mechanisms
are different in the 1 nm pore and the larger ones. In 1 nm kerogen
pores, water is completely displaced by CO2 due to the
strong interactions between kerogen and CO2 as well as
among CO2. CO2 storage capacity in 1 nm pores
can be up to 1.5 times its bulk phase in a given volume. On the other
hand, in 2 and 4 nm pores, while CO2 is dissolved in the
middle of the pore (away from the kerogen surface), in the vicinity
of the kerogen surface, CO2 can form nano-sized clusters.
These CO2 clusters would enhance the overall CO2 storage capacity in the nanopores, while the enhancement becomes
less significant as pore size increases. Kerogen maturity has minor
influences on CO2 storage capacity. Type II-A (immature)
kerogen has the lowest storage capacity because of its high heteroatom
surface density, which can form hydrogen bonds with water and reduce
the available CO2 storage space. The other three kerogens
are comparable in terms of CO2 storage capacity. This work
should shed some light on CO2 storage evaluation in shale
reservoirs.
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