Cobalt-Nickel Nanocatalyst Supported on Phosphorus-Doped Hydrochar from Malt Bagasse Waste Synthesized via One-Pot Wet Pyrolysis for Safe and Sustainable Hydrogen Fuel Evolution from Sodium Borohydride

Abstract

Hydrogen (H₂) fuel has emerged as a clean and sustainable energy source, however, efficient and safe storage of H₂ remains challenging. This study synthesized phosphorus-doped hydrochar (HC) from malt bagasse waste (BSG) using hydrothermal process with phosphoric acid (H₃PO₄) activation in a one-pot reaction, known as wet pyrolysis, under mild synthesis conditions. The HC was then used as a carbon support for cobalt (Co) and nickel (Ni) nanoparticles to catalyze H₂ evolution from the solid-state chemical store sodium borohydride (NaBH₄). The nanocatalysts were characterized using various techniques, including transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and Brunauer-Emmett-Teller (BET) analysis. In the H₂ evolution reaction from NaBH₄, the catalysts demonstrated notable catalytic efficiency, with hydrogen generation rates of 2193.17 mL min⁻¹ g⁻¹ for monometallic (Co NPs-HC) and 1205.74 mL min⁻¹ g⁻¹ for bimetallic composition (Co/Ni NPs-HC (80:20)). Additionally, the bimetallic Co-Ni nanocatalyst exhibited stronger stability, maintaining performance over up to six reuse cycles. These findings highlight the potential of the developed nanocatalysts for practical applications in safe hydrogen generation processes, in addition to promoting the circular economy through the reuse and aggregation of value to BSG generated in tons annually by the beer industry.

Keywords:
biomass waste; one-pot hydrothermal synthesis; biochar; catalysis; hydrogen fuel; sodium borohydride