Development of highly efficient, earth-abundant, and cost-effective electrocatalysts for the kinetically sluggish and energy-intensive anodic oxygen evolution reaction (OER) is crucial for realizing the large-scale commercialization of proton exchange membrane based water electrolysis (PEMWE). Herein, we report the results of one-dimensional (1D) nanorods (NRs) containing an ultralow amount of noble metal (iridium, Ir) and 10 wt % fluorine (F) doped (Mn0.8Ir0.2)­O2:10F as an efficient anode electrocatalyst, synthesized via a simple hydrothermal and wet chemical approach for the acidic OER. The as-synthesized (Mn0.8Ir0.2)­O2:10F NRs demonstrate promising electrocatalytic performance for the OER with significantly lower overpotential (η) and higher current density than state of the art IrO2 and many other electrocatalysts containing noble metal/reduced noble metal. Owing to the presence of 1D channels of the nanorod architecture and the unique electronic structure obtained upon formation of an F-containing solid solution, the (Mn0.8Ir0.2)­O2:10F NRs exhibit low charge transfer resistance (∼2.5 Ω cm2), low Tafel slope (∼38 mV dec–1), low water contact angle (∼18°), high electrochemical active surface area (ECSA ≈ 704.76 m2 g–1), high roughness factor (∼2114), and notable OER performance with ∼6-, ∼2.1-, and ∼2.2-fold higher electrocatalytic activity in comparison to IrO2, (Mn0.8Ir0.2)­O2 NRs and a 2D thin film of (Mn0.8Ir0.2)­O2:10F, respectively. The significantly higher ECSA and BET specific activity (0.11 mA cm−2 BET), mass activity (40 Ag–1), and TOF (0.01 s–1) at an overpotential (η) of 220 mV suggest the intrinsically higher catalytic activity of (Mn0.8Ir0.2)­O2:10F NRs in comparison to other as-synthesized electrocatalysts. In addition, (Mn0.8Ir0.2)­O2:10F NRs function as robust electrocatalysts by delivering a current density of 10 mA cm–2 at η ≈ 200 mV and displaying long-term durability, devoid of any degradation of the catalytic activity, suggesting the structural robustness for displaying prolonged OER activity. Herein, on the basis of the synergistic effects of tailoring of 2D material length scales into a 1D nanorod framework and the corresponding formation of an F-substituted unique solid solution structure (as validated by density functional theory), (Mn0.8Ir0.2)­O2:10F NRs offer promise for an efficient OER in PEMWE.

The exploration of high performance electro-catalysts to facilitate oxygen evolution reaction (OER) in proton exchange membrane based water splitting is of vital importance for various energy storage devices and for sustainable hydrogen production.

Identification, development, and engineering of high-performance, earth-abundant, and cost-effective precious group metal (PGM)-free electrocatalysts for catalyzing oxygen evolution reaction (OER) in acidic electrolytes are vital for the commercialization of proton exchange membrane based water electrolysis (PEMWE) technology. Utilizing the density functional theory (DFT) calculations to rationalize the thermodynamics and kinetics of adsorption of OER, juxtaposed with cohesive energy and electronic structure, we report the generation of 10 wt % fluorine (F)-doped (Mn1–x Nb x )­O2:10F nanorods (NRs) as active and durable PGM-free solid solution electrocatalysts for acid-mediated OER. The DFT calculations reveal an optimal solid solution composition of (Mn0.8Nb0.2)­O2:10F containing Nb and F in α-MnO2 structure, exhibiting the optimized surface electronic structure (ΔG for the OER rate-determining step ∼ 1.72 eV) and cohesive energy (E coh ∼ −16.30 eV/(formula unit)) for OER, contributing to its higher catalytic performance in comparison to α-MnO2. Consequently, (Mn1–x Nb x )­O2:10F compositions with well-defined one-dimensional (1D) nanorod architectures are synthesized with the optimal composition of (Mn0.8Nb0.2)­O2:10F, demonstrating improved electrocatalytic performance for acidic OER in good agreement with the DFT calculations. The superior electrochemical performance of (Mn0.8Nb0.2)­O2:10F NRs includes significantly lower charge transfer resistance (∼11.8 Ω cm2), lower Tafel slope (∼371.17 mV dec–1), lower overpotential to deliver a current density of 10 mA cm–2 geo (∼0.68 V), higher mass activity (∼29 A g–1), large electrochemically active surface area (ECSA ∼ 26.28 m2g–1), and turnover frequency (TOF ∼ 0.0065 s–1) with higher BET and ECSA normalized activity (∼0.5 mA cm–2 BET and 0.11 mA cm–2 ECSA) contrasted with (Mn1–x Nb x )­O2:10F (x = 0, 0.1, and 0.3) compositions, at an overpotential of 0.67 mV. Further, (Mn0.8Nb0.2)­O2:10F NRs exhibit good electrochemical stability in acidic OER regimes, with no substantial catalytic activity degradation, validating its structural robustness for prolonged OER and making it a promising PGM-free OER electrocatalyst for acid-mediated PEMWE.