3 D Porous Nickel–Cobalt Nitrides Supported on Nickel Foam as Efficient Electrocatalysts for Overall Water Splitting

Abstract

Exploring highly efficient and durable bifunctional electrocatalysts from earth-abundant low-cost transition metals is central to obtaining clean hydrogen energy through large-scale electrolytic water splitting. Porous nickel-cobalt nitride nanosheets on macroporous Ni foam (NF) are synthesized through facile electrodeposition followed by a one-step annealing process in a NH atmosphere. The transformation from a metal hydroxide into a metal nitride could efficiently enhance the electrocatalytic performance for both the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER). Interestingly, the incorporation of nickel further boosts the catalytic activity of cobalt nitride. When used as bifunctional electrocatalysts, the obtained nickel-cobalt nitride electrocatalyst shows good stability and superior catalytic performance toward both HER and OER with low overpotentials of 0.29 and 0.18 V, respectively, to achieve a current density of 10 mA cm . The good electrocatalytic performance was also evidenced by the fabrication of an electrolyzer for overall water splitting, which exhibits a high gas generation rate for hydrogen and oxygen with excellent stability during prolonged alkaline water electrolysis. The present work provides an efficient approach to prepare a 3 D interconnected porous nickel-cobalt nitride network with exposed inner active sites for overall water splitting.

In Situ Grown Bimetallic MOF‐Based Composite as Highly Efficient Bifunctional Electrocatalyst for Overall Water Splitting with Ultrastability at High Current Densities

“…The OER performances of the present NFN-MOF/NF electrode are compared with those of recently reported stateof-the-art NF-based OER electrocatalysts [28,[42][43][44][46][47][48][49][50][51][52][53][54][55][56][57] in terms of catalyst loading on NF, η 10 , η at higher current densities if available, Tafel slope, and stability in Table S1 (Supporting Information). Evidently, the present NFN-MOF/NF electrode competes favorably.…”

“…It is better than the electrode having the bimetallic MOF but without the NH 2 group, MIL-88B(Fe 2 Ni)-MOF/ NF, implying the importance of the amino group in boosting the HER performance. It also stands out among the recently reported top transitionmetal-based bifunctional electrocatalysts on NF for overall water splitting, including NiFe/NiCo 2 O 4 /NF (1.67 V), [42] NiCo 2 S 4 / NF (1.63 V), [43] annealed Co-Ni-B@NF (1.72 V), [44] FeNi 3 N/NF (1.62 V), [46] NiSe/NF (1.63 V), [48] NiCo 2 N-NF (1.70 V), [54] and Co 1 Mn 1 CH/NF (1.68 V) [55] (Table S6, Supporting Information). The metal ions (Fe 3+ and Ni 2+ ) of the NFN-MOF may be partially reduced to its metallic state forming M/MO 6 clusters.…”

Nickel‐Based Transition Metal Nitride Electrocatalysts for the Oxygen Evolution Reaction

“…Notable reports here include work that began from research on the impact of the Co/N ratio in cobalt nitride catalysts. Other TMNs, such as NiCo 2 N( 180 mV overpotential,1 .32 Vo nset potential, 55 mV Ta fel slope), [53] NiMoN/CF (210 mV overpotential, 1.32 Vo nset potential, 55 mV Tafel slope), [54] and Ni 3 MnN (320 mV overpotential, 1.60 Vo nsetp otential, 64 mV Ta fel slope) [55] have also been studied for the OER. For example, Sun et al reported that it "further improved the OER activity in both neutral and alkaline solutions, with high stabilityi n3 0000 cycles".…”

“…Wang et al [53] also synthesized the Ni-based ternary nitride 3D NiCo 2 Nb ye lectrodeposition on nickel foam (NF) support (Table 3). In addition, the fabrication of 3D interrelated macroporous NF with high surface area exposed extra active sites, which facilitates charge transfer and gas diffusion (H 2 ).…”

Cation‐Modulated HER and OER Activities of Hierarchical VOOH Hollow Architectures for High‐Efficiency and Stable Overall Water Splitting

“…However, the scarcity of noble metals limits the widespread application . Therefore, tremendous efforts have been made to design earth‐abundant electrocatalysts with high activity and stability, such as transition metal chalcogenides, carbides, phosphides, and nitrides for HER, and cobalt‐phosphate, perovskite oxides, and 3d transition metal–based (oxy)hydroxides for OER. Considering the compatibility of the electrocatalysts in the same electrolyte for both HER and OER simultaneously, exploring highly efficient and stable bifunctional electrocatalysts toward overall water splitting is highly desirable.…”