Catalytic converters last longer than the catalysts used in fuel cells (fuel cell catalyst is a powder so it is harder to contain). Hydrogen does embrittle mos

Catalytic converters last longer than the catalysts used in fuel cells (fuel cell catalyst is a powder so it is harder to contain). Hydrogen does embrittle most metals, but it does not affect aluminum at moderate temperatures and pressures. Obviously a piston and cylinder head experience high temperatures and pressures but it would in theory be possible to develop ceramic pistons and heads that can mitigate the embrittlement problem, as a sibling comment mentioned.