Current ratings are for a maximum capacity, so something of a higher capacity will still be able to handle something lower. Just like current ratings for power supplies.
Voltage ratings are this way to for devices like transistors, transformers, diodes, resistors, capacitors, and inductors. Not all though (since we all know that most equipment requires a minimum voltage to run properly).
So you could use a higher voltage and higher current diode if you needed to, as long as it was able to meet the other operating specifications that you need.