# Theory-based design of sintered granular composites triples three-phase boundary in fuel cells

## TL;DR

This paper presents a theoretical approach to optimize the microstructure of solid-oxide fuel cell electrodes, significantly increasing the three-phase boundary length to enhance efficiency, supported by simulations and improved contact models.

## Contribution

It introduces a systematic method to maximize TPB length based on microstructural parameters and proposes more realistic models for intergranular contacts.

## Key findings

- TPB length can be increased by over 300% with optimized microstructure.
- The commonly used contact model is oversimplified and unphysical.
- Numerical simulations support the proposed maximization strategy.

## Abstract

Solid-oxide fuel cells produce electric current from energy released by a spontaneous electrochemical reaction. The efficiency of these devices depends crucially on the microstructure of their electrodes and, in particular, on the three-phase boundary (TPB) length, along which the energy-producing reaction occurs. We present a systematic maximisation of the TPB length as a function of four readily-controllable microstructural parameters, for any given mean hydraulic radius, which is a conventional measure of the permeability to gas flow. We identify the maximising parameters and show that the TPB length can be increased by a factor of over 300% compared to current common practices. We support this result by calculating the TPB of several numerically simulated structures. We also compare four models for a single intergranular contact in the sintered electrode and show that the model commonly used in the literature is oversimplified and unphysical. We then propose two alternatives.