Carbon-free fuels

Hydrogen could be the leader of the energy transition away from fossil fuels, as carbon-free fuels eliminate any CO₂ emissions. For portable applications in particular, borohydride salts as hydrogen carriers have been a popular area of research.
When reacted with water, one mole of KBH₄ releases four moles of H₂. KBH₄ self-hydrolysis was measured and analysed to understand the properties of the reaction solution. This work found that borohydride solutions are non-Newtonian fluids, meaning viscosity is factor that must be considered in reaction systems. An increase in applied force to the solution, such as stirring, results in a lower viscosity.
Following this an active, scalable and durable catalyst for KBH₄ hydrolysis was investigated for controlled hydrogen release. However, the harsh alkaline conditions (pH >13) and rapid H₂ bubble formation cause mechanical damage to many traditional catalysts. Here, flexible chitosan spheres embedded cobalt active sites showed high activity. However, the durability decreased over 48 hrs of use. So, a metal-based support was used to provide more long-term stability.
Stainless steel was combined with cobalt active sites via 3D printing in a novel catalyst synthesis method. Cobalt-stainless steel catalyst/reactor monoliths were prepared. Although active, their low porosity resulted in degradation. So, porosity was introduced by adding aluminium to the catalysts monoliths and leached, inspired by Raney catalysts. This showed high activity and showed no decrease in activity after 96 hrs. Further, a cobalt-free porous monolith showed comparable results, proposed to be due to Al-OH active sites.