Study on direct air capture using Ti-doped K2CO3/ZrO2 composite adsorbent: A combination of experimental, characterization and first-principles calculations

[Geoengineering News]

https://www.sciencedirect.com/science/article/abs/pii/S1385894726034042

Authors: Zhuang Qi, Xiaoping Chen, Zelin Xu, Zi Liu, Jiliang Ma, Fengyuan Zhang, Cai Liang

07 April 2026

https://doi.org/10.1016/j.cej.2026.175943

Highlights

•The saturated CO2 adsorption capacity of the KZrTi5-700 adsorbent is 2.11 mmol/g.

•KZrTi5-700 shows stable 1.15–1.32 mmol/g CO2 uptake over 27 variable cycles.

•Arrhenius equation indicates Ti doping lowers the KHCO3 decomposition energy.

•DFT calculations confirm the doped model has a lower oxygen vacancy formation energy.

•Ti doping boosts DAC by regulating oxygen vacancies and lowering desorption barriers.

Abstract

Direct air capture (DAC) technology is widely recognized as a promising strategy for achieving negative carbon emissions. Alkali metal-based composite solid adsorbents exhibit strong chemical affinity and high reaction selectivity toward carbon dioxide but often suffer from high regeneration energy consumption and low cycle efficiency, limiting their practical application. In this study, a K2CO3/ZrO2 composite adsorbent doped by TiO2 was developed to enhance DAC performance. Detailed characterization combined with first-principles calculations revealed that the incorporation of Ti facilitates the formation of oxygen vacancy and reduces the energy barrier for KHCO3, thereby improving the kinetics of CO2 adsorption and desorption. The modified sample achieved a saturated CO2 adsorption capacity of 2.11 mmol/g and was fully regenerated at around 150 °C in a fixed-bed system, achieving a carbonization conversion rate of 92.59%, which corresponds to a 74.38% enhancement compared to the unmodified sample. Furthermore, the adsorbent maintained a stable working capacity ranging from 1.15 to 1.32 mmol/g over 27 consecutive cycles under varying conditions, surpassing the performance of most reported alkali-based sorbents and showing its promising potential for DAC applications.

Source: ScienceDirect