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Steel honeycomb monoliths have been manufactured by Fused Deposition Modelling-FDM 3D printing technology using 90 % 17–4 PH steel nanoparticles-loaded polymer filament. Pure steel monoliths were obtained after thermal removal of the polymer and steel sintering. NiO-CeO2active phase nanoparticles were loaded on powder steel and on the steel monoliths, and the supported catalysts were tested in the hydrogenation of CO2to CH4, paying special attention to the steel pretreatment before active phase loading. The catalytic experiments confirm that totally functional catalysts have been prepared, showing 100 % selective conversion of CO2to CH4above 225 ºC and stability in long-term experiments (18 hours at 325 ºC). The catalytic behaviour is improved by H2O2-pretreatment of the steel honeycomb monoliths before the active phase loading. XPS characterization confirms that the surface of the catalysts is oxidised on the fresh catalysts and gets even more oxidised after the catalytic tests. The H2O2-pretreatment of the steel support partially avoids the additional oxidation under reaction conditions, keeping chromium and cerium cations less oxidised than on the catalyst prepared with untreated steel. In addition, evidence about the electronic interaction between the steel support and the NiO-CeO2(np) active phase are obtained.