Hydrochar supported bimetallic Ni–Fe nanocatalysts with tailored composition, size and shape for improved biomass steam reforming performance

Abstract

Multicomponent nickel–iron alloy nanoparticles supported on hydrochar were synthesized by a facile one-step hydrothermal strategy. Spinel nickel ferrite (NiFe₂O₄) with a small crystalline size around 10 nm was uniformly dispersed on a bimetallic catalyst. The roles of the Ni/Fe doping concentration and calcination temperature in tailoring the phase, morphology and size of the Ni–Fe alloy nanoparticles were investigated. To probe the catalytic abilities of the prepared bimetallic catalysts, a two-stage reaction system was applied for steam gasification of sewage sludge. Compared to monometallic nickel nanoparticles, the synthesized bimetallic catalyst, especially Ni_0.25Fe_0.25/HC calcined at 700 °C, showed excellent dispersibility of the Ni–Fe alloy NPs and exhibited a strong metal–support interaction, which allowed for better suppression of carbon deposition and nanoparticle agglomeration in the reforming process. The best catalytic performance resulted in a promoted hydrogen selectivity of 113.7 g H₂ per kg sludge with a low tar yield of 2.3 mg g⁻¹ under mild gasification conditions. These shape- and size-modulated nanocatalysts harbor promising potential for their application as a highly efficient catalyst for hydrogen production via steam gasification of sewage sludge.