How do I stop my emergency fund from losing value to inflation while it sits unused?

You cannot fully beat inflation on money that must stay safe and liquid, but you can minimize the drag. Keep the fund in a high-yield savings or money market account whose rate rises with short-term interest rates, rather than a big-bank account paying almost nothing, so at least you earn a competitive yield. For the portion you are least likely to touch soon, I-bonds from the U.S. Treasury adjust with inflation, and short Treasury bills or a CD ladder can capture a bit more. Accept that the emergency fund's job is protection and instant access, not growth; its real return may be near zero, and that is fine. The money meant to outpace inflation over decades belongs in invested accounts, not in your cash cushion.