In-Situ Anchored Catalysts for Efficient Gas-Phase Formic Acid Dehydrogenation: Enhanced Activity Via Metal-Support Interactions between Ni3p and G-C3n4

Abstract

Formic acid (FA) is considered a promising liquid organic hydrogen carrier due to its low toxicity and capability to release hydrogen under mild conditions. However, developing safe, efficient, and cost-effective catalysts for FA dehydrogenation remains a challenge. This study presents a novel non-precious metal catalyst based on nickel phosphide (Ni3P), demonstrating catalytic performance comparable to a noble catalyst (i.e., Pt/Norit) even at a high weight hourly space velocity of 39 h-1. Ni3P nanoparticles were anchored onto graphitic carbon nitride (g-C3N4) via an in-situ synthesis method, yielding a material denoted Ni3P@CN-In with porous and highly dispersed Ni3P nanoparticles. The resulting Ni3P@CN-In achieved complete FA conversion and 99.6% H2 selectivity at 210 °C, maintaining stable catalytic performance over a 50-hour test. In contrast, bare g-C3N4 showed negligible catalytic activity for FA dehydrogenation, unsupported Ni3P reached only 67.6% FA conversion, and a mechanically-ground catalyst (i.e., Ni3P@CN-Gr) achieved 88.7% conversion. These results highlight the importance of in-situ loading of Ni3P on g-C3N4 in enhancing its intrinsic catalytic activity. Material characterization results revealed strong metal-support interactions between Ni3P and g-C3N4 in the Ni3P@CN-In catalyst. Density functional theory results confirmed the formation of Ni-N bonds between Ni3P and g-C3N4, along with the emergence of electron-deficient Niδ+ species. These Niδ+ centers enhance stabilization of the key reaction intermediate (HCOO*) and lower the energy barrier for its decomposition into CO2 and H2, thereby promoting efficient FA dehydrogenation.

Keywords: Formic acid, liquid organic hydrogen carriers, dehydrogenation, Metal-Support Interactions, nickel phosphide, g-C3N4