Ionothermal Route to Phase-Pure RuB₂ Catalysts for Efficient Oxygen Evolution and Water Splitting in Acidic Media

Abstract

Developing high-efficiency and stable oxygen evolution reaction (OER) materials remains a great challenge, especially in an acidic medium. In this study, we report the first synthesis of phase-pure RuB2 by using a salt melt of potassium chloride and lithium chloride as the solvent. When used as an electrocatalyst in 0.5 M sulfuric acid, the as-prepared RuB2 needs an overpotential of only 223 mV for the OER to produce an operationally relevant current density of 10 mA cm–2. This is almost the smallest overpotential value for Ir/Ru-based acidic OER catalysts reported to date. More importantly, in the acidic full water splitting, RuB2 exhibits outstanding activity and stability, which merely needs a cell voltage of 1.525 V to reach a current density of 10 mA cm–2, lower than those of the most bifunctional electrocatalysts reported in acid electrolytes. Theoretical calculation results further identify the formation of *OOH as the rate-determining step and the lower energy barrier for the RuB2 catalyst, improving the OER activity. This work represents a significant addition to exploring a new class of transition metal borides with outstanding activity in acidic water electrolysis and beyond.

Regulative Electronic States around Ruthenium/Ruthenium Disulphide Heterointerfaces for Efficient Water Splitting in Acidic Media

“…From the deconvoluted spectrum of Ru 3p state, the couple peaks at 462.1 and 484.3 eV are associated with Ru 3p 3/2 and Ru 3p 1/2 , respectively (Figure 2 c). [3, 18] Figure 2 d shows that the separate subpeaks at 163.0 and 164.2 eV are consistent with S 2p 3/2 and S 2p 1/2 states, respectively [19] . To compare the chemical states of heterostructure material with phase‐pure materials, further XPS analyses were conducted.…”

“…As for the hydrogen production, the acidic water splitting devices employing mature proton exchange membrane (PEM) technology afford excellent hardware environment for large‐scale commercial applications [1a, 2] . The use of PEM and favorable reaction mechanism bring multiple strengths, such as cost advantage, high proton conduction, fewer side effects and convenient gas separation [2b, 3] . However, both electrodes of PEM‐water splitting (PEMWS) devices require certain electrocatalysts to effectively facilitate the sluggish kinetic processes [1a, 4] .…”

Regulative Electronic States around Ruthenium/Ruthenium Disulphide Heterointerfaces for Efficient Water Splitting in Acidic Media

“…But the oxidation behavior at high voltage would cause devitalization, and the effusion of lattice oxygen would result in the dissolution of active species, rendering them unstable during OER process [10] . Thus, designing oxygen‐free Ru‐based catalysts with suitable morphology and electron structure might alleviate the deactivation behavior, meanwhile promote their intrinsic activity and durability [3, 11] …”

Anion Modulation of Pt‐Group Metals and Electrocatalysis Applications

“…The results showed that RuB 2 needed less energy for the rate-determining step (formation of *OOH), so the OER activity was improved (Figure 3d, e). [31] In addition, the OER activity of RuTe 2 was also [8] and c) RuP 2 @PNC [20a] used in DFT calculations and calculated free energy diagrams of the catalyst samples for HER. [17b] Reproduced with permission.…”

“…d), e) Free energetic pathways of RuB 2 and RuO 2 for acidic OER at U = 0 V. Reproduced with permission. [31] Copyright: 2020, American Chemical Society. f) CO 2 RR and g) nitrite reduction on pure Pd (111) and TeÀ Pd (111) surfaces.…”