Super-Hydrophilic Hierarchical Ni-Foam-Graphene-Carbon Nanotubes-Ni₂P–CuP₂ Nano-Architecture as Efficient Electrocatalyst for Overall Water Splitting

Abstract

Water splitting via an electrochemical process to generate hydrogen is an economic and green approach to resolve the looming energy and environmental crisis. The rational design of multicomponent materials with seamless interfaces having robust stability, facile scalability, and low-cost electrocatalysts is a grand challenge to produce hydrogen by water electrolysis. Herein, we report a superhydrophilic homogeneous bimetallic phosphide of Ni2P–CuP2 on Ni-foam-graphene-carbon nanotubes (CNTs) heterostructure using facile electrochemical metallization followed by phosphorization without any intervention of metal-oxides/hydroxides. This bimetallic phosphide shows ultralow overpotentials of 12 (HER, hydrogen evolution reaction) and 140 mV (OER, oxygen evolution reaction) at current densities of 10 and 20 mA/cm2 in acidic and alkaline mediums, respectively. The excellent stability lasts for at least for 10 days at a high current density of 500 mA/cm2 without much deviation, inferring the practical utilization of the catalyst toward green fuel production. Undoubtedly, the catalyst is capable enough for overall water splitting at a very low cell voltage of 1.45 V @10 mA/cm2 with an impressive stability of at least 40 h, showing a minimum loss of potential. Theoretical study has been performed to understand the reaction kinetics and d-band shifting among metal atoms in the heterostructure (Ni2P–CuP2) that favor the HER and OER activities, respectively. In addition, the catalyst demonstrates an alternate transformation of solar energy to green H2 production using a standard silicon solar cell. This work unveils a smart design and synthesizes a highly stable electrocatalyst against an attractive paradigm of commercial water electrolysis for renewable electrochemical energy conversion.

Ultrathin NiCo Bimetallic Molybdate Nanosheets Coated CuOx Nanotubes: Heterostructure and Bimetallic Synergistic Optimization of the Active Site for Highly Efficient Overall Water Splitting

“…[ 4b,22 ] The existence of various defects can optimize and affect the adsorption free energy of the reaction intermediates. [ 11a ]…”

“…As we all know, a satisfactory electrocatalyst also needs to have a larger specific surface area, higher electron transfer rate and more active sites so the to achieve a more effective catalytic effect. [ 11 ] As a result, the design of bimetallic compounds for controllable modification and regulation of electronic structures to achieve the synergistic regulation of electrical conductivity and stability of electrocatalyst activity has gradually become a research hotspot. In addition, for transition metal base catalyst, the introduction of the second element in the host lattice can also make the electronic structure of the lattice obvious adjustment, so as to change the adsorption free energy of reaction intermediates and obtain good electrocatalytic property.…”

Highly Enhanced OER Performance by Er-Doped Fe-MOF Nanoarray at Large Current Densities

“…At 100 mA cm −2 , the Er 0.4 Fe-MOF/NF exhibited the lowest overpotential (248 mV), compared with bare NF (418 mV), precursor Fe-MOF/NF (336 mV) and commercial RuO 2 /NF (288 mV). It was notable that Er 0.4 Fe-MOF/NF exhibited excellent electrocatalytic activity, surpassing most of the previous OER catalysts [40][41][42][43][44][45][46][47][48][49], as shown in Figure 3b and Table S3. Er 0.4 Fe-MOF/NF needed an overpotential of 210 mV at low current density (10 mA cm −2 ) by the back sweep test (Figure S5).…”

Temperature-controlled fabrication of Co-Fe-based nanoframes for efficient oxygen evolution

“…To expose more accessible active sites, various nanostructured TMPs have been designed and fabricated, including nanowires, nanospheres, nanotubes, and nanosheets [11][12][13][14]. Among various nanostructures, the three-dimensional (3D) opened nanoframes (NFs) are of particular interest, which achieve large surface area and high atomic utilization efficiency by hollowing out the interior embedded unfunctional atoms [15].…”

“…In addition to nanostructure engineering, the composition regulation, e.g., by rational design and synthesis of bimetallic phosphides, has also been recognized as an effective way to promote the catalytic activity [9]. Previous studies suggested that the redistribution of electrons can be induced by the strong interfacial interactions at the hybrid TMP heterointerface, leading to the improved electron conductivity and synergistic OER catalytic enhancement [9, 13,19]. For instance, Liang et al [20] reported that Ni 2 P-CoP heterointerfaces can create effective electron transport channels, leading to synergistically enhanced OER performance with a low overpotential of 320 mV to achieve a current density of 10 mA cm −2 in 1 mol L −1 KOH.…”