To address some of the most common issues facing methane steam reforming (MSR) over Ni-based catalysts – such as coke poisoning and high operating temperatures – we interest ourselves with the electric field effects on said catalytic process. Via density function theory (DFT) calculations, three important aspects of MSR were studied: (1) the coke formation over Ni surfaces (Ni(111) and Ni(211)); (2) the interaction between H2O molecules and Ni surfaces; and (3) the overall thermodynamic and kinetic properties of the MSR reaction over Ni(111). According to the results from the field-dependent microkinetic model we established and the corresponding experimental work, we found that in comparison with the absence of electric fields, a positive electric field can greatly enhance the Ni catalytic performance via: (i) impeding the coke formation over the catalytic surfaces; (ii) decreasing the initial input steam-to-methane ratio; and (iii) lowering the operating temperatures. Furthermore, to better understand the mechanisms of sulfur and coke poisoning over the Ni-supported yttrium-stabilized-zirconia (Ni/YSZ) electrode in electrochemical cells, we elucidated the field effects on the oxygen vacancy formation at the triple phase boundary (TPB) of this catalysts via hydrogen oxidation under experimental conditions since such vacancies are active for sulfur and coke poisoning. Our results showed that both large negative and positive electric fields could lead to more active TPB vacancies of the Ni/YSZ electrode to a certain degree. This work emphasizes the significance of considering the factor of electric fields when investigating electrochemical cell systems.