Direct Electrosynthesis of Selective Transition-Metal Chalcogenides as Functional Catalysts with a Tunable Activity for Efficient Water Electrolysis

Abstract

Transition-metal chalcogenides (TMCs) are cheap and abundant and have recently been demonstrated as promising electrocatalysts for sustainable and efficient water electrolysis. The existing TMC synthesizing methods are limited by difficulties in precise composition control and complexities in synthetic parameters, highlighting the need for a facile and viable strategy for direct synthesis of TMCs on conducting substrates. Here, we report a generalized approach for direct synthesis of a variety of high-efficient, robust TMCs and stoichiometric composition-controlled TMC catalysts on conducting three-dimensional porous substrates via an anion-assisted electrochemical deposition technique. Using this strategy, 10 different types of TMC electrocatalysts were designed and synthesized using representative transition-metal elements (Co, Fe, Mo, Ni, and W) and chalcogen elements (S and Se). In particular, NiS and FeSe exhibited excellent activity with overpotentials of 83 and 171 mV to reach a current density of 10 mA cm–2 in HER and OER, respectively. In addition, control over the stoichiometric composition was also demonstrated by adjusting the ratio of binary chalcogen anions, in turn allowing for the modification of catalytic properties. Furthermore, a water electrolysis cell with the NiS cathode and FeSe anode showed remarkable overall water splitting performance with a cell voltage of 1.52 V at 10 mA cm–2 and superior long-term stability for 100 h even at a high current density (100 mA cm–2), which was a significantly higher performance in comparison with the other reported TMC-based cells and the benchmark noble Pt/C∥IrO2 cell.

Coupling NiCoS and CoFeS Frame/Cagelike Hybrid as an Efficient Electrocatalyst for Oxygen Evolution Reaction

“…Transition metal-based sulfide/selenide/phosphide electrocatalysts because of their enhanced stability and inherent electrical conductivity are the most effective electrocatalysts for OER. , Sulfide/selenide/phosphide anions through their electronegativities play a significant role in modulating and controlling the electron cloud distribution, resulting in improved intrinsic activity and electronic structure of TM catalysts. − For example, the fabricated Ni–Fe mixed diselenide nanocages derived from the corresponding PBA nanocages are reported by Nai and co-workers as an excellent electrocatalyst for OER through processing a nanocube precursor with a site-selective ammonia etchant . Lian and co-workers demonstrated the formation of a 3D framework of bimetallic cobalt–iron phosphide and showed it to be a good electrocatalyst for efficient overall water splitting .…”

Electronic and Surface Modifications of Ni–Co–Fe Oxides: A Catalyst with Maximum Exposure of Fe Active Sites for Water Electrolysis

“…(1) a facile and economical synthetic route for the development of electrodes; (2) abundant active sites with high intrinsic reactivity; (3) high structural, chemical, and mechanical durability at high geometric activity; (4) excellent ionic and electrical conductivity with a high charge transfer rate at the solid−liquid boundary; and (5) short diffusion channels for mass transfer and gas desorption rate to enhance the effective contact between the active site and electrolyte to make it durable. 9 To date, numerous economic and efficient transition metalbased electrocatalysts including metal oxides, 10 hydroxides, 11 carbides, 12 sulfides, 13 selenides, 14 chalcogenides, 15 borides, 16 alloys, 17 and phosphides 18 of Ni, Co, and Fe and their alloys have been prepared due to their unique chemical/physical properties, reversible redox chemistry, exceptional catalytic performance, and unique electronic structures. 19,20 Among transition metals, iron has been regarded as a promising alternative as an OER electrocatalyst because of its flexible valence state, excellent activity, multiple charge-bearing abilities, and high mechanical durability.…”

“…To date, numerous economic and efficient transition metal-based electrocatalysts including metal oxides, hydroxides, carbides, sulfides, selenides, chalcogenides, borides, alloys, and phosphides of Ni, Co, and Fe and their alloys have been prepared due to their unique chemical/physical properties, reversible redox chemistry, exceptional catalytic performance, and unique electronic structures. , Among transition metals, iron has been regarded as a promising alternative as an OER electrocatalyst because of its flexible valence state, excellent activity, multiple charge-bearing abilities, and high mechanical durability . Numerous Fe-based OER composites in alkaline media have been investigated in monometallic oxides, bimetallic oxides, chalcogenides, carbides, pnictides and in combination with other transition metal oxides, and hydroxides .…”

Construction of MnxCoyO4/Ti electrocatalysts for efficient bifunctional water splitting

“…With the exploitation of fossil energy reserves and the increasingly serious environmental problems, 1,2 it is urgent to develop clean and sustainable energy to replace the traditional fossil energy. 3,4 Hydrogen energy has many advantages such as high calorific value of combustion, 5 no pollution of combustion products and abundant storage of raw materials; 6,7 therefore, it is considered as an ideal substitute for traditional fossil energy. [8][9][10] However, the slow dynamics cause water to decompose at a voltage higher than the theoretical voltage, requiring additional energy.…”