Accelerating the reconstruction of NiSe2 by Co/Mn/Mo doping for enhanced urea electrolysis

Abstract

As a highly promising renewable energy technology, the urea oxidation reaction (UOR) not only enables efficient utilization of urea wastewater but also provides an effective alternative for hydrogen production via water electrolysis, thereby reducing the energy consumption of conventional electrolysis. Therefore, the development of UOR catalysts with high catalytic activity and long-term stability is of great significance for advancing clean energy technologies. In this study, a nickel-based selenide catalyst (NiCoMnMo–Se) with coexisting nanoparticles and nanosheets was synthesized using a NaBH₄ reduction and selenization strategy. X-ray photoelectron spectroscopy (XPS), ultraviolet–visible (UV–vis) and in-situ bode phase plots, revealed that the synergistic effect of Mn and Mo regulated the electronic structure of Ni, enhancing the conductivity of nickel selenide and accelerating charge transfer kinetics, which facilitates the rapid transformation of Ni²⁺/Co²⁺ into active Ni³⁺/Co³⁺ and significantly reduces the onset potential of NiCoMnMo–Se. During the UOR process, Mo and Se are oxidized to form molybdate and selenate, which subsequently dissolve into the electrolyte. This transformation results in the partial conversion of the original spherical nanoparticle surfaces into nanosheets, thereby exposing more Ni(Co)OOH active sites and significantly enhancing the UOR reaction. Additionally, the introduction of Mn stabilizes the active sites, thereby improving the overall stability of the catalyst. As anticipated, the synthesized NiCoMnMo–Se catalyst demonstrates outstanding electrocatalytic performance and stability in the UOR process, achieving a current density of 50 ​mA ​cm⁻² at a potential of only 1.38 ​V vs. RHE (reversible hydrogen electrode), with a voltage increase of only 3.0% after 50 ​h of operation at a 50 ​mA ​cm⁻². When NiCoMnMo–Se and commercial Pt/C were assembled into a dual-electrode system for alkaline urea electrolysis, it only requires 1.59 ​V vs. RHE to achieve a current density of 50 ​mA ​cm⁻². This paper designs an efficient and stable Ni-based selenide catalyst, which is expected to promote the further development of selenides in relevant energy technologies.