Abstract Simultaneous activation of CO 2 and H 2 O was carried out in a non thermal plasma dielectric barrier discharge reactor operated under ambient conditions. The plasma reactor packed with partially reduced NiO/Al 2 O 3 catalyst showed better CO 2 conversion than both the unreduced NiO/Al 2 O 3 and with plasma (no catalyst), whereas, highest syngas selectivity was observed with unreduced NiO/Al 2 O 3 . An interesting observation is the formation of carbon nanofibres (CNFs) along with syngas with a reduced NiO catalyst integrated to the plasma, whereas, pure NiO only led to the formation of methane. The reduction of CO 2 by in situ formation of hydrogen from water splitting may produce CH 4 and plasma-assisted chemical vapour decomposition of CH 4 may lead to the formation of CNFs.