The paper discusses the evaluation of electrostatic DC corona discharge devices for the application of molecular decomposition. A point-to-plane geometry corona device with a rectangular cross section demonstrated low decomposition efficiencies in earlier experimental work. The numerical simulation of the device suggested that there were low electron density and electric field zones, resulting in electrical sneakage. Thus, the kinetic rate coefficients in the chemical reaction process were significantly reduced. A triangle-shaped DC corona discharge device was developed to improve the electrical sneakage problem, and a mathematical model was developed to describe the detailed electrical characteristics and to refine estimates on the optimum shape of the device. The preliminary experimental results indicated that the decomposition efficiency was much improved.