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[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]

Research on water splitting reaction is on priority to explore an alternative source of energy with little to no carbon emissions. Among the two half reactions of electrochemical water splitting, oxygen evolution reaction (OER) is highly desirable yet challenging to prepare a cost effective and viable electrocatalyst to boost the OER activity. Herein, we have prepared a novel electrocatalyst, CoO x -CoP/N-CNTs, by the phosphidization of cobalt oxides (CoO x) encapsulated N- doped carbon nanotubes (CoO x /N-CNTs). The CoO x /N-CNTs composite is derived via pyrolysis of cobalt based zeolitic imidazole framework (ZIF-12) at 950 °C under argon atmosphere. The CoO x /N-CNTs is phosphidized at various temperatures ranging from 320 °C to 400 °C. The optimized temperature to attain the best catalytic activity is 380 °C. The phosphatized material, CoO x -CoP/N-CNTs, shows superior performance towards OER with an overpotential of 250 mV @ 20 mAcm−2 vs 532 mV @ 20 mAcm−2 of un-phosphidized material, CoO x /N-CNTs, which shows significant effect of phosphidization. The maximum current density of 160 mAcm−2 in 1 M KOH solution is achieved. • A novel electrocatalyst, CoO x -CoP/N-CNTs, is fabricated. • The phosphatized material, CoO x -CoP/N-CNTs, shows superior performance towards OER. • During OER activity, an overpotential of 250 mV at 20 mAcm−2 and current density of 160 mAcm−2 is observed. • The electrochemical activity remarkably greater than the un-phosphatized material. [ABSTRACT FROM AUTHOR]

Transition metal oxyhydroxides have been used as promising electrocatalysts for water splitting however, their catalytic activity is restricted due to low surface area and poor conductivity. Herein, we report novel composite FeOOH@ZIF-12/graphene composite as electrocatalyst for water oxidation, whereby ZIF-12 provide extra surface for the FeOOH dispersion whilst graphene act as excellent electron mediator. The composite shows a low overpotential value of 291 mV to attain a current density of 10 mA cm−2 and a low Tafel slope value of 78 mV dec−1. The catalyst offers a maximum current density of 101 mA cm−2, while it gives a turnover frequency (TOF) value of 0.031 s−1 at an overpotential of 291 mV only. The excellent activity and remarkable stability of composite is attributed to highly conductive and porous support. [Display omitted] • FeOOH nanoparticles are incorporated in ZIF-12/graphene matrix. • The synthesized composite is utilized as electrocatalyst for water oxidation. • The composite shows a low overpotential value of 291 mV @ 10 mA cm−2. • The catalyst offers a maximum current density of 101 mA cm−2 with a TOF value of 0.031 s−1. [ABSTRACT FROM AUTHOR]