what specs do I need to look for in the datasheet to determine if the diode is correct?
If you are looking for a low frequency (50 or 60Hz) power rectifier, you need to look at things like:
Maximum repetitive peak inverse voltage (Vrrm)
Maximum RMS voltage (Vrms)
Maximum DC blocking voltage (Vdc)
Maximum average forward rectified current If(av)
I got these from the Vishay datasheet for the 1N4007
If you are looking for a diode to rectify high frequencies (greater than say 1kHz), you would first look at similar parameters for voltage and current, and then you would look for parameters like:
Reverse recovery time (Trr)
The Vishay datasheets for the 1N914 and 1N4148 both specify this parameter (4ns), the datasheet for the 1N4007 does not.
From this and other numbers in the 1N4007 datasheet, experience tells us that it is not suitable for high frequencies.
You are looking for 115200 bits per second, as a quick approximation, if you had a binary 101010101 pattern, the fundamental frequency of that waveform would be 115200/2 = 57.6kHz which is very fast for a 1N4007.
A period of 4nS corresponds to a frequency of 250MHz. For rectifying we would want our frequency to be a lot less than half of this, say 100MHz.
So for a low power application such as yours, a 1N4148 or 1N914 would be a good choice.
1N4007, reverse recovery and high frequency switching.
Because of its slow reverse recovery time, the 1N4007 can be used as a cheap RF switching diode for non-critical applications.
When forward bias is applied to the 1N4007, current flows.
When an RF signal is superimposed on the bias, the RF passes through the diode, EVEN WHEN THE DIODE IS REVERSE BIASED by the RF voltage being greater than the bias voltage.
This is all down to this reverse recovery thing, the charge carriers in the semiconductor material do not have enough time to recombine and this allows the diode to keep on conducting in the reverse direction.
PIN diodes are made to maximise this effect and are used for RF switching.
JimB