Fe3C/graphitic carbon xerogels as electrocatalysts for green hydrogen production

Abstract

Hydrogen production via water electrolysis offers a sustainable alternative to fossil fuels, with the hydrogen evolution reaction (HER) serving as a key step. Enhancing the efficiency of this process requires improving the performance and durability of the electrocatalysts involved in HER. This study addresses the limitations of traditional acidic electrolytes which offer high catalytic activity but poor long-term stability by exploring the use of bicarbonate buffer media in combination with iron carbide (Fe3C)-based carbon xerogel catalysts. Three distinct hydrothermal synthesis routes were developed to optimize the catalysts morphology and porosity. Among them, the method involving the delayed addition of NH4OH in a water–ethanol solution (CX-S3) produced the most promising results. This approach yielded a carbon xerogel with high mesoporosity, small, interconnected particles, and a favorable micro–mesoporous structure. These features facilitated improved proton access to the encapsulated Fe3C active sites, resulting in enhanced electrochemical performance. In 0.1 M KHCO3 electrolyte, CX-S3 achieved a stable hydrogen output of 7262.4 ppm at −0.77 V vs. RHE during 8 h of continuous operation. While the catalyst demonstrated faster initial kinetics in acidic conditions, its performance deteriorated at higher current densities due to degradation. In contrast, the bicarbonate buffer provided a more stable environment, enabling sustained hydrogen production and preserving catalyst integrity.