Ternary NiCoP nanosheet arrays: An excellent bifunctional catalyst for alkaline overall water splitting

Abstract

Exploring bifunctional catalysts for the hydrogen and oxygen evolution reactions (HER and OER) with high efficiency, low cost, and easy integration is extremely crucial for future renewable energy systems. Herein, ternary NiCoP nanosheet arrays (NSAs) were fabricated on 3D Ni foam by a facile hydrothermal method followed by phosphorization. These arrays serve as bifunctional alkaline catalysts, exhibiting excellent electrocatalytic performance and good working stability for both the HER and OER. The overpotentials of the NiCoP NSA electrode required to drive a current density of 50 mA/cm 2 for the HER and OER are as low as 133 and 308 mV, respectively, which is ascribed to excellent intrinsic electrocatalytic activity, fast electron transport, and a unique superaerophobic structure. When NiCoP was integrated as both anodic and cathodic material, the electrolyzer required a potential as low as ~1.77 V to drive a current density of 50 mA/cm 2 for overall water splitting, which is much smaller than a reported electrolyzer using the same kind of phosphide-based material and is even better than the combination of Pt/C and Ir/C, the best known noble metal-based electrodes. Combining satisfactory working stability and high activity, this NiCoP electrode paves the way for exploring overall water splitting catalysts.

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.…”

Electrospun Carbon Nanofibers Encapsulated with NiCoP: A Multifunctional Electrode for Supercapattery and Oxygen Reduction, Oxygen Evolution, and Hydrogen Evolution Reactions

“…The requirement of high durability is mandatory for an electrocatalyst to prove its potential when it comes to practical applications. [13] A minimum Tafel slope of 83 mV dec −1 is obtained for NiCoP/CNF900 when compared with other electrodes. The uninterrupted evolution of gas bubbles and a merely slight deterioration of current density observed all the way through the completion of CA analysis ensure the highly stable nature of NiCoP/CNF900 electrode for OER activity.…”

“…Hence, the chronoamperometry (CA) was carried out at a constant potential of 1.56 V (vs RHE) for 25 h as shown in Figure 9b. [12,13] The enhanced electrocatalytic property can be ascribed to the high electrochemical surface area provided by plenteous bimetal nanoparticles encapsulated carbon nanofibers, which in turn also provides numerous active sites on the surface to facilitate the evolution reaction. Figure 9c shows the Tafel plot for OER of NiCoP/CNF electrodes.…”

“…The onset of hydrogen evolution was seen emerging at a low potential of −0.10 V (vs RHE) at a scan rate of 5 mV s −1 and a much less overpotential of 130 mV was required to drive a current density of 10 mA cm −2 for NiCoP/CNF900, which is comparatively lower than the reported Ni-and Co-based HER electrodes listed in Table 3. [12,13,23,29,30,[67][68][69][70][71] Inset of Figure 9e illustrates the required HER overpotential to achieve a current density of 10 mA cm −2 for the prepared electrocatalysts. Since long-term stability is a decisive criterion to evaluate the performance of the electrocatalyst, the CA analysis is studied for a constant potential of −0.28 V (vs RHE) for 20 h as shown in Figure 9e.…”

“…[8,9] The NiCoP being enriched with the synergistic effect of the most admirable transition metals of Ni and Co; shows richer faradaic redox reactions, higher electrical conductivity, and stability to accomplish an enhanced electrochemical performance than their monometallic counterparts. [13] As well as, the partially positive Ni-Co metal centers and partially negative P sites acts as a hydride acceptor and proton acceptors respectively, to promote the hydrogen evolution reaction (HER) activity of the NiCoP nanostructures. [11] Similarly, dissimilar metal 3D orbitals of Ni and Co lower the kinetic energy barriers, thus improving the catalytic activity during oxygen and hydrogen evolution reactions.…”