One thing is obvious that in the case of anode reaction as much we move from zero to larger positive values, we can say potential is increasing. But in the case of cathode reaction if the potential values are moving from zero to more negative values then what we can say either potential is becoming higher and higher?

For a brief answer, please order the following as higher to lower potential:

The electrochemical reduction of CO2 to CH4 over Cu (-0.90V vs RHE), Fe (-0.53V vs RHE), and Ag (-1.22V vs RHE).