Impact of Rare-Earth Phosphate as a Hydrophilic Promoter on Boosting Electrooxidation of 5-Hydroxymethylfurfural: A DyPO4/Ni2P Example

The hydrophilic property of the catalytic interface has been seldom focused on particularly, although many green and sustainable catalysis transformations involve water. Addressing the issue, we prepared Dy–Ni–P catalysts for the 5-hydroxymethylfurfural oxidation reaction (HMFOR) to 2,5-furandicarboxylic acid (2,5-FDCA) in this work. The catalysts were clarified as (DyPO₄)_m/Ni₂P composites with molar ratio m within 0.08–0.28 by ICP-OES, XRD, XPS, and HRTEM characterizations. The catalytic performance of samples was comprehensively analyzed by the HPLC technique, ¹H NMR spectra, and various electrochemical tests, indicating that the introduction of DyPO₄ in a proper amount (m = 0.16) would significantly enhance the catalytic efficiency versus singular Ni₂P in terms of 2,5-FDCA yield (91 vs 26%), selectivity (99 vs 47%), and Faradaic Efficiency (F.E.: 98 vs 70%). The enhancements were accompanied by improved kinetic features such as the Tafel slope (53 vs 95 mV dec^–1) and intrinsic activity (3.3 vs 1.7 mA cm^–2). The boosting endowment (DyPO₄)_m/Ni₂P stands among the top members of reported Ni-based HMFOR catalysts. The promoter effect of DyPO₄ was further investigated by H₂O-TPD, contact angle, zeta potential, OCP, and EIS measurements. It was testified that the nonhydrophilic Ni₂P surface would be converted to a hydrophilic composite interface with the introduction of DyPO₄; in line with the essential change, transfer of reactants and activation of water were obviously intensified with the lowered charge transfer resistance along the catalytic interface, which was responsible for the enhanced catalytic behavior of (DyPO₄)_m/Ni₂P versus Ni₂P. The above discovery made the topic regarding water indicate that the hydrophilic property of the catalytic interface played a significant role in facilitating heterogeneous catalysis transformations involving water; exampled by the current (DyPO₄)_m/Ni₂P for HMFOR, rare-earth phosphate could be referred to as an outstanding hydrophilic promoter to innovate excellent catalysts for technology-important chemical engineering involving water.