Presented here are the observations and interpretations from a comprehensive analysis of 16 representative particles returned from the C-type asteroid Ryugu by the Hayabusa2 mission. On average Ryugu particles consist of 50% phyllosilicate matrix, 41% porosity and 9% minor phases, including organic matter. The abundances of 70 elements from the particles are in close agreement with those of CI chondrites. Bulk Ryugu particles show higher ' 18 O, " 17 O, and C 54 Cr values than CI chondrites. As such, Ryugu sampled the most primitive and least-thermally processed protosolar nebula reservoirs. Such a finding is consistent with multi-scale H-C-N isotopic compositions that are compatible with an origin for Ryugu organic matter within both the protosolar nebula and the interstellar medium. The analytical data obtained here, suggests that complex soluble organic matter formed during aqueous alteration on the Ryugu progenitor planetesimal (several 10's of km), <2.6 Myr after CAI formation. Subsequently, the Ryugu progenitor planetesimal was fragmented and evolved into the current asteroid Ryugu through sublimation.
Electricity
has been generated from evaporation-driven water flow
in films of carbon soot particles and other porous media. This paper
reports the placement of carbon nanofiber mats (CNMs) on fiberglass
screens for the construction of efficient water-evaporation-induced
generators (WEIGs). These CNMs are prepared from carbonizing electrospun
polyacrylonitrile nanofiber mats and then treating them with oxygen
plasma. After electrode attachment to the two ends of a CNM, one electrode
is immersed into water. Water rises in the mat due to capillary action
and evaporates from the mat surface due to thermal energy provided
by the environment. The steady rise of water pushes the dissociated
ions of the surface functionalities upward, resulting in a streaming
current and an electric potential. This paper investigates how the
generated short-circuit current, I
s, and
open-circuit voltage, V
o, of the WEIG
change with structural parameters of the CNMs. Under optimized conditions,
these CNMs produce electricity at an areal power density of 83 nW/cm2, which is almost 10 times those offered by some existing
ones. Thus, the easy-to-handle CNMs are an attractive porous scaffold
for WEIGs.
The development of MoS2 in the metallic phase (1T‐MoS2) is of paramount interest as it exhibits superior electrochemical activities compared to its semiconducting polymorph (2H‐MoS2). In this work, an ionic liquid (IL)‐assisted solvothermal method was employed to produce the thermodynamically metastable 1T‐MoS2. Structural characterization of the material suggests the intercalation of the IL into MoS2. De‐intercalation of ILs from 1T‐MoS2 leads to the formation of 2H‐MoS2. Carbon cloth‐supported 1T‐MoS2(1T‐MoS2@CC) shows higher electrocatalytic activity towards acidic hydrogen evolution reaction (HER) by delivering a current density of 50 mA/cm2 at an overpotential of 210 mV whereas 2H‐MoS2@CC requires an overpotential of 260 mV to reach the same current density. In addition, the 1T‐MoS2@CC electrode delivers a high electrochemical double‐layer storage ability compared to 2H‐MoS2@CC in 1 M Na2SO4. The enhanced electrochemical activity of 1T‐MoS2 over 2H‐MoS2 may be due to the existence of conducting basal planes and the high interlayer spacing (about 1 nm) caused by the intercalation of ILs into the MoS2 layers.
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