Global warming, which is often confused with “climate change”, can cause longlasting, irreversible, catastrophic and far-reaching effects on the earth and the lives of the future generations. There is a unanimous agreement that global warming is mainly due to human activities and above all, burning fossil fuels for industrial applications and emission of CO2 as one of the major contributors of global warming.
To mitigate the amount of CO2 emission and to offset its effect, the governments around the world have united to take necessary actions in an effective and efficient way by a variety of policy changes and adoption of technologies such as carbon capture and storage. For instance, the UK government has set out measures to tackle climate change with a plan for the UK to be a pioneering economy in the world towards a zero-emission economy by 2050.
Among the technologies used for carbon capture, those derived from solid sorbents for CO2 capture attract growing interest in industrial applications. The popularity of using these technologies is attributed to their lower energy penalty, high selectivity, recyclability and ease of manufacturing. Developments of new materials with low cost is fundamental, even though numerous solid sorbents have been examined for CO2 capture to date.
Porous boron nitride (BN) has been recognised as a promising alternative to be used in carbon adsorption process due to its unique advantages including its bond polarity, tuneability and high thermal and chemical stabilities. So far, a systematic understanding of how its distinctive properties (pore structure and chemistry) contributes to capture carbon dioxide is still lacking. To develop a favourable porous BN, further work is required to establish the viability of these materials as cost-effective adsorbents.
This research presents synthesis and modification strategies of porous BN and a characterisation of the material for carbon capture application. Various synthesis conditions have been developed to obtain high surface area (>700 m2/g) pristine BN material via template free method. The study pursued two distinct strategies to modify pristine porous BN, aiming to enhance its CO2 adsorption performance. Firstly, a focus on controlling the pure BN porosity has been implemented by tuning with a polymeric surfactant as non-metal modification approach. The capacity of pure CO2 on nonmetal modified porous BN has been enhanced by about 34.5% compared to pristine BN in ambient conditions. The study highlights the significant role of porosity/pore size of BN for CO2 adsorption.
Secondly, a novel approach has been implemented for modifying pore structure and surface chemistry of pristine BN by introduction of Ni (II) into BN framework. The pure CO2 capture experiment has been assessed, considering three different temperatures and the results confirmed that the basic sites on porous BN contribute to its ability to adsorb more CO2 relative to pure BN. The method has been validated as a feasible route to improve porous BN performance in CO2 adsorption process even at realistic flue gas temperatures (above 298 K). Finally, the stability and reusability of pristine BN samples with various porosity and chemistry have been examined over the eight adsorption-desorption cycles.
Overall, this dissertation demonstrated that porous BN materials possess a combination of desirable properties with flexibility for functionalisation and lower regeneration energy. Thus, it can be considered as an effective adsorbent for future large-scale carbon capture technologies.