Integration of metals into the biomass matrix has been found to be an alternate strategy to the conventional catalysts that are prone to deactivation. Different metals like Ni (0.98 mol/ kg), Ru (0.76 mol/kg) and Fe (0.83 mol/kg) are separately impregnated into banana pseudostem to analyse their impact on H-2 yields. In-situ gasification of metal impregnated biomass was conducted over sub/- and supercritical water range of 300-600 degrees C, with 1:10 biomass-to-water ratio for 60 min. X-ray diffraction and X-ray photoelectron spectroscopy of char generated at 300 and 600 degrees C confirm the transition of nanometals from M(n+) to MP(0) during in-situ gasification. The reduction of metal oxides to nanometals enhanced the gas yields by providing more active sites. Maximum H-2 yields of 11.1, 8.83 and 8.04 mmol/g was achieved for metal (Ni/Ru/Fe) impregnated banana pseudo-stem with the carbon gasification efficiency approaching 73.64, 64.21 and 62.65% respectively at 600 degrees C. (C) 2019 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.