Hydrogen Generation from Seawater Electrolysis over a Sandwich-like NiCoN|Ni_xP|NiCoN Microsheet Array Catalyst

Abstract

Seawater electrolysis presents a transformative technology for sustainable hydrogen production and environmental remediation. However, the lack of active and robust hydrogen evolution reaction (HER) catalysts severely impedes the development of this technology. Here, we report a sandwich-like nanostructured HER catalyst constructed by decorating both sides of nickel phosphide (Ni x P) microsheet arrays with nickel cobalt nitride (NiCoN) nanoparticles. The resulting integrated hierarchical sandwich-like catalyst (NiCoN|Ni x P|NiCoN) simultaneously provides a large surface area with abundant active sites, improved intrinsic activity of every active site, and high electrical conductivity for efficient charge transfer. Consequently, the NiCoN|Ni x P|NiCoN electrode exhibits very good HER activity, requiring a small overpotential of 165 mV to achieve a current density of 10 mA cm–2 in natural seawater electrolyte, along with very impressive stability benefiting from the good chlorine-corrosion resistance of the inner Ni x P microsheet arrays. Our work paves a new route toward the design of hierarchical nonprecious catalysts for hydrogen generation from seawater electrolysis.

Stable and Highly Efficient Hydrogen Evolution from Seawater Enabled by an Unsaturated Nickel Surface Nitride

“…Transition metal nitrides (TMNs) have excellent electrical conductivity and corrosion resistance and have demonstrated good stability for seawater splitting. [ 18–20 ] However, most of the bulk TMNs reported exhibit unsatisfactory HER activity due to a suboptimal hydrogen bonding energy. [ 21,22 ] Consequently, material optimization strategies, such as vacancy engineering, alloying, interface engineering, and heteroatom doping are usually needed to improve their activity.…”

“…To evaluate the electrocatalytic activity of Ni-SN@C under alkaline conditions, we first conducted electrochemical (Figure 3b), which is very close to the Pt/C benchmark (18 mV, 38 mV dec −1 ) and superior to other works (Table S2, Supporting Information). [10,20,32,38,39] At large current densities, the Ni-SN@C has a smaller overpotential than Pt/C and certainly demonstrates better HER activity compared to Ni@C and Ni 3 N. Where Ni@C and Ni 3 N have Tafel slopes above 120 mV dec −1 , Ni-SN@C has a Tafel slope of 39 mV dec −1 , indicating that the unique surface nitride has an optimized electronic structure which facilitates the water dissociation step. To gain more insight into the HER process on Ni-SN@C, electrochemical impedance spectroscopy (EIS) and the electrochemically active surface area (ECSA) of the different samples were explored.…”

Insights on the Electrocatalytic Seawater Splitting at Heterogeneous Nickel-Cobalt Based Electrocatalysts Engineered from Oxidative Aniline Polymerization and Calcination

“…The composition at equal quantity of Ni and Co gives the best performance while the compositions 3:1 and 1:3 tend towards the same overpotential at j = −100 mA cm −2 . The performance obtained here is lower than the overpotential of 165 mV achieved at 10 mA cm −2 for HER in seawater at integrated hierarchical sandwich-like NiCoN|NixP|NiCoN electrocatalysts [ 59 ], keeping in mind that these categories of open-pore foam-type electrodes of three-dimensional materials may lead to an overestimation of the HER performance indicators [ 60 ]. The enhancement of the electrocatalytic properties for the bimetallic electrodes results from the cooperative action of both chalcogenides of nickel (NiS x , x = 0, 2/3, 8/9, and 4/3) and cobalt (CoS x : x = 0 and x = 8/9) and the metal-support interaction that facilitate the adsorption of water molecules and the electron transfer as Equation (6) was found to be the limiting step of the HER mechanism.…”

Metallic S‐CoTe with Surface Reconstruction Activated by Electrochemical Oxidation for Oxygen Evolution Catalysis

“…Currently, cobalt‐based electrochemical catalysts with d‐electron configuration including oxides/hydroxides, [ 5 ] phosphides, [ 6 ] nitrides, [ 7 ] chalcogenides, [ 8 ] exhibit outstanding OER activity and durability. In particular, chalcogenides with the earth abundance and tunable electronic structure show superior OER activity.…”