Electronic Modulation of Nickel Disulfide toward Efficient Water Electrolysis

Abstract

friendly and sustainable sources of power are being looked at in order to meet the demand. Among all the developing technologies, solar-light-coupled electrochemical water splitting is widely perceived as one of the best solutions due to the generation of hydrogen -a sustainable and clean source of energy. [1] It is known that noble group compounds, namely Pt and RuO 2 /IrO 2 , are the state-of-the-art electrocatalysts toward two critical half-reactions of water splitting -hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). [2] However, the high price and natural shortage impede their further application. Therefore, developing lowcost, efficient electrocatalyst is urgently desired.Motivated by the challenge, a wide range of materials have been investigated and developed. [3] Among them, nickelbased materials have attracted a great deal of attention mainly because their eight valence electrons in 3d orbitals enable the easy alteration of electronic structure through phase engineering (laser-induced, mechanical strain, weak Ar plasma treatment, e-beam irradiation, and plasmonic hotelectron-induced), heterostructuring (NiS 2 -MoS 2 , Ni 3 S 2 -MoS 2 , V-Ni 2 P). [3c,4] A representative compound in this nickel-based family, pyrite-type nickel sulfides (NiS 2 ) is emerging as a highly Developing highly efficient earth-abundant nickel-based compounds is an important step to realize hydrogen generation from water. Herein, the electronic modulation of the semiconducting NiS 2 by cation doping for advanced water electrolysis is reported. Both theoretical calculations and temperaturedependent resistivity measurements indicate the semiconductor-to-conductor transition of NiS 2 after Cu incorporation. Further calculations also suggest the advantages of Cu dopant to cathodic water electrolysis by bringing Gibbs free energy of H adsorption at both Ni sites and S sites much closer to zero. It is noteworthy that water dissociation on Cu-doped NiS 2 (Cu-NiS 2 ) surface is even more favorable than those on NiS 2 and Pt(111). Thus, the prepared Cu-NiS 2 shows noticeably improved performance toward alkaline hydrogen and oxygen evolution reactions (HER and OER). Specifically, it requires merely 232 mV OER overpotential to drive 10 mA cm −2 ; in parallel with Tafel slopes of 46 mV dec −1 . Regarding HER, an onset overpotential of only 68 mV is achieved. When integrated as both electrodes for water electrolysis, Cu-NiS 2 needs only 1.64 V to drive 10 mA cm −2 , surpassing the state-of-the-art Ir/C-Pt/C couple (1.71 V). This work opens up an avenue to engineer low-cost and earth-abundant catalysts performing on par with the noble-metal-based one for water splitting.The ORCID identification number(s) for the author(s) of this article can be found under https://doi.

Ni(OH)2 Templated Synthesis of Ultrathin Ni3S2 Nanosheets as Bifunctional Electrocatalyst for Overall Water Splitting

“…For the electrocatalysts, earth‐abundant Ni‐based sulfide electrocatalysts with remarkable electrocatalytic performance and excellent conductivity have caught particular attention. [ 9–14 ] Extensive efforts have been devoted to controlling the structure and morphology of Ni‐based sulfide catalysts to get a low overpotential. For instance, an asymmetric zigzag structure of Ni 3 S 2 was synthesized and presented excellent performance for full water electrolysis due to its high electrochemically active surface area.…”

Advanced Transition Metal‐Based OER Electrocatalysts: Current Status, Opportunities, and Challenges

“…The semiconductor‐to‐conductor transition of NiS 2 can be realized after Cu incorporation. [ 196 ] The metallic‐like behavior of Cu‐NiS 2 is attributed to the contribution from d orbitals of Cu atoms. This phenomenon can also be observed when NiS 2 is doped with V. [ 197 ] Electron transfer from V to Ni enables Ni site to gain more electrons.…”

Realizing zT Values of 2.0 in Cubic GeTe

“…Cu 2 Te is introduced to reduce the Ge‐vacancies and therefore optimize the carrier concentration. Addition of Cu has been reported to drastically increase the carrier mobility in GeTe [77–79] . Subsequently, we further enhance the thermoelectric properties by introducing heavy element Pb as phonon scattering centres in (Ge 0.90‐y In 0.01 Ti 0.03 Pb 0.06 Sb y Te) 0.99 – (Cu 2 Te) 0.01 (y=0.02, 0.04, and 0.06), denoted Y2, Y4, and Y6 hereon.…”