One-Pot Synthesis of High Performing Metal-Doped Iron Triad Electrocatalyst for Green Hydrogen Production By Water Electrolysis

Energy demand is increasing rapidly worldwide as modernization makes most daily needs dependent on energy. To meet the energy needs of the next generation, electrification plays a pivotal role in the transition to sustainable and green energy systems by facilitating the reduction of greenhouse gas emissions, improving energy efficiency, and enabling the integration of renewable energy sources. This sustainable and green energy economy enables the efficient use of electricity, especially when generated from intermittent renewable energy sources such as solar and wind, thereby coupling to energy storage such as batteries or energy conversion technologies such as water electrolysis to produce green hydrogen. 1 In addition to the high energy carrier capacity and unmatched zero emissions of hydrogen, recent advances and cost reductions in the renewable energy sector are increasing the forecast of green hydrogen as a viable economic form and widespread practical widespread application. Nevertheless, the development of materials that improves the efficiency and durability of low-temperature water electrolysis is the basis for the industrial production of green hydrogen. Fundamentally, noble metal-based materials are the state-of-the-art electrocatalysts (ECs) as they exhibit unsurpassed intrinsic catalytic properties for the half-cell chemical reactions for water electrolysis. These half-cell reactions exhibit different catalytic mechanisms and as consequences different catalytic properties are desirable. At the cathode of a water electrolyser the hydrogen evolution reaction (HER) involves two electron transfer processes, while the oxygen evolution reaction (OER) at the anode is a multistep process requiring four electrons transfers. 1 The latter exhibits sluggish kinetics, resulting in a large overpotential compared to the theoretical value, and thus low energy conversion efficiency. Therefore, it is very important to develop highly efficient OER ECs which would reduce this overall energy loss. In recent studies, a wide range of materials have been investigated, including transition metal oxides, perovskites, metal hydroxides, and metal-nonmetal materials such as chalcogenides. Recent advances in TM-based catalysts for OER and HER focus on improving activity and stability through modulation of electronic structures and optimization the compositions of materials. The development of nanostructures with different morphologies such as nanoparticles, nanowires, or nanosheets, as well as structures such as amorphous and crystalline phases improves the reaction kinetics by optimizing the surface area, conductivity, and availability of the active site. 2 Synergy effects in multimetal systems is reported to improve catalytic efficiency, especially for HER and OER, by exploiting the complementary properties of different metals. 3 These advances overall push the boundaries of TM-based catalysts in applications for green hydrogen production. Considering these recent developments, we have developed a one-pot synthesis as a cost-effective approach to preparation of metal transition metal (TM) electrocatalysts (ECs) with high catalytic activity. In this study, we synthesize metal-doped iron triad bimetallic borides (Mz-MtB, where Mt is a transition metal element from the iron triad, and Mz is a non-iron triad metal) via a chemical reduction method. The success of the synthesis strategy was confirmed by determining the surface and bulk composition of material using analytical techniques such as near-ambient pressure X-ray photoelectron spectroscopy (NAP-XPS) and inductively coupled plasma atomic emission spectroscopy (ICP-AES). The structure and porosity were characterized by X-ray diffraction (XRD) and nitrogen physisorption measurements, while the morphology was examined with scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The catalytic activity of the oxygen evolution reaction (OER) was investigated using cyclic voltammetry with a thin-film rotating ring-disk electrode (CV-TF-RRDE). The inclusion of guest metal element with an atomic radius very different from those of iron triad metals, served as modulators for the activation of the precatalyst during water oxidation in the stable iron triad metal boride nanomaterial. The electrochemical and physicochemical characterization of this iron triad-based nanomaterial provides insights into optimizing the performance of multimetal catalysts by incorporating a guest TMs, that interact differently with metalloids such as boron. This approach can promote the development of ECs with superior activity compared to precious metal-based ECs. This work provides a one-step synthesis method to develop high-performance transition metal-doped iron triad metal borides for OER, a crucial half-cell chemical reaction which is involved in numerous electrochemical energy storage and conversion systems. Acknowledgements This project has received funding from the European Union’s Horizon 2020 research and innovation program under the Marie Skłodowska-Curie grant agreement No 101102946 (HYDROBAT, DOI: 10.3030/101102946). References M. Chatenet, B. G. Pollet, et al., Chem. Soc. Rev. , 2022 , 51, 4583-4762. J. M. V. Nsanzimana, C. O. Ogolla, et al., ECS Meeting Abstracts , 2024 , MA2024-01, 1858. J. M. V. Nsanzimana, R. Dangol, et al., ACS Appl. Mater. Interfaces , 2019 , 11, 846-855.