Carbon Dioxide, Bicarbonate and Carbonate Ions in Aqueous Solutions at Deep Earth Conditions

Agglomeration Drives the Reversed Fractionation of Aqueous Carbonate and Bicarbonate at the Air-water Interface

In the course of our investigations of the adsorption of ions to the air-water interface, we previously reported the surprising result that doubly-charged carbonate anions exhibit a stronger surface affinity than do singly-charged bicarbonate anions. In contrast to monovalent, weakly hydrated anions, which generally show enhanced concentrations in the interfacial region, multivalent (and strongly hydrated) anions are expected to show much weaker surface propensity. In the present work, we use resonantly enhanced deep-UV second harmonic generation spectroscopy to measure the Gibbs free energy o…

从水溶液到固态的碳酸钙从头机器学习模拟

Ab initio machine learning simulation of calcium carbonate from aqueous solutions to the solid state

本文构建基于 SCAN 密度泛函理论的 SCAN-ML 机器学习势能模型，模拟水溶液至固态的碳酸钙，准确描述离子、固相和界面并揭示经碳酸氢根结合及质子转移的离子对形成机制。

The fate of carbon dioxide in water-rich fluids at extreme conditions

Investigating the fate of dissolved carbon dioxide under extreme conditions is critical to understanding the deep carbon cycle in the Earth, a process that ultimately influences global climate change. We used first-principles molecular dynamics simulations to study carbonates and carbon dioxide dissolved in water at pressures (P) and temperatures (T) approximating the conditions of the Earth's upper mantle. Contrary to popular geochemical models assuming that molecular CO$_2$(aq) is the major carbon species present in water under deep earth conditions, we found that at 11 GPa and 1000 K carbon…

A Carbon Dioxide Absorption System Driven by Water Quantity

A novel system containing nanoporous materials and carbonate ions is proposed, which is capable to capture CO2 from ambient air simply by controlling the amount of water (humidity) in the system. The system absorbs CO2 from the air when the surrounding is dry, whereas desorbs CO2 when wet. A design of such a CO2 absorption/desorption system is investigated in this paper using molecular dynamics and quantum mechanics simulations, and also verified by experiments. Its working mechanism is revealed as the reduction of free energy of the carbonate ion hydrolysis with the decrease of the number of …

Carbon dioxide adsorption and activation on Ceria (110): A density functional theory study

Ceria (CeO2) is a promising catalyst for the reduction of carbon dioxide (CO2) to liquid fuels and commodity chemicals, in part because of its high oxygen storage capacity, yet the fundamentals of CO2 adsorption and initial activation on CeO2 surfaces remain largely unknown. We use density functional theory, corrected for onsite Coulombic interactions (DFT+U), to explore various adsorption sites and configurations for CO2 on stoichiometric and reduced CeO2 (110). Our model of reduced CeO2 (110) contains oxygen vacancies at the topmost atomic layer and undergoes surface reconstruction upon intr…

Geochemistry of silicate-rich rocks can curtail spreading of carbon dioxide in subsurface aquifers

Pools of carbon dioxide are found in natural geological accumulations and in engineered storage in saline aquifers. It has been thought that once this CO2 dissolves in the formation water, making it denser, convection streams will transport it efficiently to depth, but this may not be so. Here, we assess theoretically and experimentally the impact of natural chemical reactions between the dissolved CO2 and the rock formation on the convection streams in the subsurface. We show that, while in carbonate rocks the streaming of dissolved carbon dioxide persists, the chemical interactions in silica…