Nanoelectrode Corona Discharges for Minimizing Ozone Emission from Indoor Corona Devices

Z. Bo, K. Yu, G. Lu, S. Mao, J. Chen, and F.-G. FanUniversity of Wisconsin-Milwaukee; Tongji University; Mechanical Engineering Sciences Laboratory (MESL)

RouteRoute

� Carbon nanotubes (CNTs) as the electrodes� Graphene sheets rolled-up into cylinders� High aspect ratio, high electrical conductivity, good chemical stability, superior mechanical strength and durability� Smaller number of electrons and plasma volume

IntroductionIntroduction

Electrostatic devices Inside corona system

Ozone

If at excessive concentration levels in poorly ventilated areas

Respiratory system Lung function

� FDA, OSHA, NIOSH and EPA have proposed/improved regulations or health recommendations to limit ozone emission

Acknowledgements: We acknowledge the financial support from National Science Foundation (CBET-0741336), Xerox Corporation, University of Wisconsin System, and UWM Research Growth Initiative. The authors thank H. A. Owen for technical support with SEM, A. Ash for technical support with ozone analyzer, and A. V. Skliarov for technical support with Raman. Z. Bo acknowledges the research fellow support from the UWM Research Foundation.

ExperimentalExperimental Ozone emissionOzone emission

� Nanoscale electrodes are prepared by drop casting well-dispersed CNT/ethanol suspension onto the substrate� The substrate is a holey carbon film coated copper TEM grid� CNTs: ~20 nm in diameter and ∼2.5 μm in length� Holes in the substrate: around 1 ~ 3μm� Discharge is from the side surfaces of the suspended CNTs

Electrical measurementsElectrical measurements

� Corona discharge from CNTs can initiate and operate at a much lower voltage due to the small electrode diameter, and is thus energy-efficient� There is an optimum CNT length (CNT loading) that maximizes the surface current density

J-V curveSupply voltage for the same current density

� Obvious ozone generation from tungsten wire discharges� For a given surface current density, the ozone generation decreases with the decreasing wire size� No ozone (below the detection limit of 0.5 ppb) from CNT discharges for surface current densities up to 0.744 A/m2

Positive discharges Negative discharges

StabilityStability

� CNTs show good chemical stability after 30 min discharge cycle

Raman spectra of the CNT electrode

ConclusionConclusion

� Energy-efficient (lower corona initiation voltage) and environmentally friendly (near-zero ozone emission) corona discharge through the use of CNTs as discharge electrodes is promising for practical applications in indoor electrostatic devices.

MESL

10th Annual SyracuseCoE Symposium on Environmental & Energy Systems, Oncenter, Syracuse, NY, 9/27-28, 2010