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Synthesis of mixed transition metal nitrides often leads to the formation of more than one phases in the final product. A control over molar ratio of metals (Fe:Ni) along with synthetic strategy is used to form phase pure product (Fe 3 Ni 7 N@C). The synthesized material is used as an efficient and cost-effective electrocatalyst for oxygen evolution reaction (OER). Fe 3 Ni 7 N@C requires a low overpotential of 290 mV to achieve a catalytic current density of 10 mA cm−2 which holds Tafel slope of 40 mV dec−1 superior to the noble metal benchmark catalysts. The physicochemical integrity of Fe 3 Ni 7 N@C is maintained up to 12 h activity as evident from post catalytic characterization. Fe3Ni7N@C nanoparticles for oxygen evolution reaction. [Display omitted] • A control over molar ratio of metals (Fe:Ni) is used to form phase pure product (Fe 0.3 Ni 0.7 N@C). • Fe 0.3 Ni 0.7 N@C is used as an efficient electrocatalyst for oxygen evolution reaction (OER). • Fe 0.3 Ni 0.7 N@C requires a low overpotential of 290 mV to achieve a catalytic current density of 10 mA cm−2. • The physicochemical integrity of Fe 0.3 Ni 0.7 N@C is maintained up to 12 h activity. [ABSTRACT FROM AUTHOR]

[Display omitted] • Transition metal nitrides (TMNs) have gained substantial interest to catalyse water splitting reaction. • Iron and nickel based TMNs are considered as ideal electrocatalysts because of the abundance, low cost, and high catalytic activity. • Single phase TMNs have unsatisfactory performance due to inadequate M−H/M−OH bond strength. • Recent developments pertaining to Fe and Ni-based TMNs are presented for electrochemical water splitting. Transition metal nitrides (TMNs) have gained substantial interest to generate hydrogen from direct dissociation of water via catalytic strategy. Due to the unique noble metal like structure, high electric conductivity, corrosion resistance, broad pH stability and probable structural modifications TMNs are gauged as efficient hydrogen evolution reaction (HER), oxygen evolution reaction (OER) and overall water splitting (OWS) electrocatalysts. Iron and nickel based TMNs are considered as ideal electrocatalysts because of the abundance, low cost and high catalytic activity as compared to the expensive benchmark catalysts. However, the single phase TMNs have unsatisfactory performance due to inadequate M−H/M−OH bond strength. Most researchers have focused in designing advanced heterostructures by doping other metals, metallic compounds, and conductive substrates to improve catalytic performance due to the tailored electronic structure to modify M−H/M−OH bond strength, boost electrochemical stability and synergistic effects. In this review, we highlight the recent developments pertaining to Fe and Ni-based TMNs from the stance of advanced nanoarchitecture electrocatalysts for electrochemical water splitting. The key challenges and future perspectives confronting expansion of water splitting catalysts are critiqued. [ABSTRACT FROM AUTHOR]

[Display omitted] • The polymeric compound [{NiII(4,4ʹ-dipy) 4 }{Ni(CN) 4 }] n (1) is presented as electrocatalyst towards water oxidation. • 1 has showed ca. 28 times enhanced surface concentration (Γ = 39.5 nmol/cm2), compared to the reported CoFe(CN) 6 (Γ = 1.4 ± 0.2 nmol/cm2). • The overpotential of merely 315 mV is required to produce a current density of 1 mA/cm2. • The development is designing the noble metal (Pt/Ru/Ir) free, efficient electrocatalysts for water oxidation reaction. The search of proficient, copious, economical and robust electrocatalyst is of prime prerequisite. Recently, the usage of cyanometallate based coordination polymers as electrocatalysts for water oxidation has acquired an expanding measure of attraction attributable to their high surface area and stability. In this study, a homo-metallic Ni based cyanometallate coordination polymer [{NiII(4,4ʹ-dipy) 4 }{Ni(CN) 4 }] n ·(4,4ʹ-dipy)·3H 2 O·C 2 H 6 O 2 (1) (4,4ʹ-dipy = 1,3-di(4-pyridyl)propane) is presented as an efficacious and robust electrocatalyst towards water oxidation reaction at pH = 13. The inimitable 3-D zig-zag topology of 1 has directed to ~28 times enhanced surface concentration (Γ) i.e. 39.5 nmol/cm2 as compared to the reported CoFe(CN) 6 (Γ = 1.4 ± 0.2 nmol/cm2). The 1 presents a TOF of 0.25 s−1 at an overpotential (η) of 381 mV (vs. RHE) which is much larger than those reported for other cyanide bridged and Ni based coordination polymers for instance: CoFe(CN) 6 (TOF = 2 × 10−3 s−1, η = 300 mV), CoFe(CN) 5 -PVP (TOF = 2 × 10−3 s−1, η = 284 mV), Codca2 (TOF = 2 × 10−3 s−1, η = 358 mV), Ni-UMOFNs (TOF = 0.18 s−1, η = 300 mV), bulk NiCo-MOFs (TOF = 0.15 s−1, η = 300 mV) and Ni-MOF/NF (TOF = 0.25 s−1, η = 400 mV). The overpotential (η) of of 315 mV is required to produce a current density (J) of 1 mA/cm2. Controlled potential electrolysis (CPE), PXRD and FT-IR experiments confirm that 1 remains active and chemically integrate over a 36,000 s test reaction. The outcomes of the comprehensive electrochemical investigations are prophesied to direct the imminent development in designing noble metal free, efficient and low-priced electrocatalysts for oxygen evolution reaction. [ABSTRACT FROM AUTHOR]