PhD Projects

2015-19

ZERO GAP CELL DESIGN FOR ALKALINE ELECTROLYSIS

Interelectrode_Gap_Drawings

Robert Philips

Using a zero-gap cell arrangement is shown to significantly reduce the Ohmic resistance of the setup, as well as decreasing the effect of gas evolution on the performance of the cell. This allows the cell to operate at higher current densities when compared to the conventional finite gap setup. This research quantifies the benefit of
employing zero-gap cell design over the traditional finite gap approach, with a 30 % reduction in Ohmic resistance observed when compared to the previous setup.

Electrocatalysts for both the hydrogen evolution and oxygen evolution reactions have been developed and shown to display high electrocatalytic performance, good adhesion to the substrate and good electrochemical stability at current densities appropriate for alkaline electrolysis. Simple, one-step deposition methods are used, to allow simple scaling up of the electrode size. The use of a nickel-iron oxyhydroxide electrocatalyst at the anode is demonstrated with an overpotential of 280 mV at 10 mAcm􀀀2 and a Tafel slope of 37 mVdec􀀀1. Raney nickel has been shown to be an effective hydrogen evolution electrocatalyst, with a current density of 93 mV at 10 mAcm􀀀2 and Tafel slope of 62 mVdec􀀀1.

The evolution of two-phase flow inside the zero gap electrolyser is investigated, with two models of the behaviour being validated against visual data. Using high-speed photography, the flow regimes have been visualised using bespoke flowfield designs. This information gives an insight into the two phase flow regime inside the cell at current densities up to 2 Acm􀀀2. A Matlab program is developed to quantify the flow regime transition between the bubbly and slug flow regimes.