“…NPs can also significantly influence the microbial metabolic activity for H 2 production through similar phenomenon under aerobic condition by efficient transfer of electrons [44]. Thus, a positive effect of various NPs, including silver (Ag), gold (Au), Copper (Cu), Fe, Ni, Palladium (Pd), Silica (SiO 2 ), Titanium (Ti), activated carbon, carbon nano-tubes (CNTs) and composite were observed on BHP [19,29,30,[44][45][46][47][48][49][50][51]. Briefly, these NPs might be stimulating BHP by their surface and quantum size effect [49].…”