Unraveling the Beneficial Electrochemistry of IrO₂/MoO₃ Hybrid as a Highly Stable and Efficient Oxygen Evolution Reaction Catalyst

Abstract

Minimization of noble metal contents along with enhancement in electrochemical properties with high durability is a major challenge to be overcome for commercializing water electrolyzers and cheap energy storage devices. Sluggish kinetics of the oxygen evolution reaction (OER) within the electrolytic cell and high energy demand to form OO bonds have attracted more responsiveness to this area. We report the OER beneficial mixed oxide composite of molybdenum and iridium oxides by a facile hydrothermal method. Adhered IrO 2 nanoparticles on MoO 3 large particles synergistically possessed a robust nature toward harsh acidic water electrolysis as compared to an alkaline environment. Mass specific OER activity of iridium active centers was greatly enhanced by 7-fold, twice the current density, and was attributed to electronic modulation of noble metal. Enhanced surface area and the existence of highly oxidative species in the O(1s) spectrum of IrO 2 and two doublet regions in the X-ray photoelectron spectrum of molybdenum metal were found, accountable for the robust performance. Prepared composite possessing only 30% molar fraction of noble metal presented an excellent long-term stability for 40 000 s. Reduction in the Tafel slope from 57 to 77 mV dec −1 for IM-30 and IrO 2 respectively was observed. The conducted research will open up new avenues for more applications of molybdenum oxides and their derivatives for water splitting.

Nanostructured MoO3 for Efficient Energy and Environmental Catalysis

“…The co-doping, bringing numerous active sites (about 6.550 × 10 −3 mol/g) and amorphous structure of the CMO, was responsible for the improvement of OER activity. The durability of these catalysts was not so good, and the current density could remain stable at 10 mA/cm 2 for only 3-15 h in KOH aqueous solution [76][77][78].…”

“…Tariq et al prepared IrO 2 -MoO 3 composites and 30% mole fraction of iridium contents, which would be more favorable for OER. The mass specific OER activity of iridium active centers was greatly enhanced by seven-fold [76]. Figure 4a showed the CMO with uniformly spherical structure of 500 nm in diameter.…”

“…Electrocatalytic OER is another half-reaction of water splitting. Owing to transfer of four electrons for the evolution of an O 2 molecule, OER is more sluggish compared to HER and becomes the rate-determining step of water splitting [76,77]. There are just a few of research studies about MoO 3 applied in OER, in which MoO 3 is regarded to be catalytically inert for OER [78].…”

Rationality in the new oxygen evolution catalyst development

“…IrO 2 /MoO 3 composites reportedly possess a higher activity and stability compared to IrO 2 . [21] Similarly, IrO 2 /MnO 2 composites show an increased OER activity due to the strong distortion of IrO 6 octahedra by a Jahn Teller effect induced by MnO 2 . The IrO 6 distortion effect is, however, influenced by an increase in surface area.…”

Design of Multi‐Metallic‐Based Electrocatalysts for Enhanced Water Oxidation

“…[43] In comparison, OER activities of single oxide composites were still relatively low, in the order of NiO x > CoO x > Figure 4. The OER performance of typical precious-metal-based catalysts: Ru (110), [22] IrCu, [17] IrNiCo, [26] Ba 2 YIrO x DP, [20] IrTi hybrid, [27] IrMo hybrid, [28] IrMn hybrid [29] and CoRuIr [30] were evaluated in HClO 4 ; IrNi, [31] IrO x À IrSrO 3 , [21] W 1-x Ir x O 3-δ , [16] Ir, [25] Ru [25] and RuCr [32] were evaluated in H 2 SO 4 . 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 FeO x > MnO x .…”