Sulfur‐Induced Interface Engineering of Hybrid NiCo₂O₄@NiMo₂S₄ Structure for Overall Water Splitting and Flexible Hybrid Energy Storage

Abstract

is very significant for renewable energy source systems benefiting from plentiful water resource and high purity hydrogen production. It contains two half reactions, that is hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). [5][6][7] However, the efficiency of overall water splitting largely lowers due to the kinetically sluggish OER. [8,9] Developing highly active and cost-effective catalysts is very essential to improve the energy conversion efficiency. [10] Currently, precious metal electrode materials such as Pt and RuO 2 /IrO 2 have been studied due to their superior electrocatalytic performance for HER and OER. [11,12] However, the scarcity, high price, and poor durability seriously restrict their practical applications. Therefore, highly efficient nonprecious metal catalysts for HER and OER are required to expedite the reaction kinetics and lower the overpotential. Transition metal oxides have been widely investigated as promising electrocatalysts for overall water splitting. Among various materials, spinel-structured NiCo 2 O 4 has received considerable interest because of its low cost, abundance, and excellent electrical conductivity. [13,14] For example, Liu and coworkers prepared hierarchical NiCo 2 O 4 hollow microcuboids through assembling porous nanowire subunits for overall water splitting. The as-fabricated products show the overpotential of 300 and 110 mV for OER and HER, respectively, and a cell voltage of 1.65 V at 10 mA cm −2 . [15] Bao et al. synthesized Ni x Co 3−x O 4 nanoneedle arrays on Ni foam through a simple hydrothermal route, the as-prepared products exhibit the overpotential of 320 mV for OER and 170 mV for HER at 10 mA cm −2 . [16] However, intrinsic poor conductivity of metal oxides usually leads to a low current density. Therefore, to prepare hybrid-structured electrode materials by combining high conductivity materials or element doping has been considered an effective strategy. For instance, Tu et al. fabricated hierarchical NiCo 2 O 4 /Ni 2 P core-shell nanocone arrays on Ni foam as a bifunctional catalyst for overall water splitting. The asobtained product shows the overpotential of 250 mV for OER and a cell voltage of 1.59 V at 10 mA cm −2 . [17] Liu and co-workers reported Fe-doped NiCo 2 O 4 @HNCP nanosheets through a simple hydrothermal approach. The as-synthesized electrodes exhibit high OER and HER activities with overpotentials of To rationally design hybrid structures with unique surface/interface features is very significant due to their multi-functionalization in energy storage and conversion systems. Generally, single metal oxide as electrode material is still unsatisfactory for its slow electron transportation and inevitable structural collapse. To address these issues, sulfur element-induced interface-tailoring hybrid NiCo 2 O 4 @NiMo 2 S 4 nanosheet structures with high electrochemical activity are reported through a simple vulcanization process of NiCo 2 O 4 @NiMoO 4 nanosheets. The hybrid NiCo 2 O 4 @NiMo 2 S 4 structure presents excellent...

Rational construction of free-standing P-doped Fe2O3 nanowire arrays as highly effective electrocatalyst for overall water splitting

“…[28][29][30] In addition, the electrocatalytic performance of the prepared sample was compared with the reported catalyst, and it can be found that the prepared material has good electrocatalytic performance (Table 1). [31][32][33][34][35][36]…”

A 3D hierarchical network derived from 2D Fe-doped NiSe nanosheets/carbon nanotubes with enhanced OER performance for overall water splitting

“…4b). In addition, it also exhibits superior η to reported catalysts, such as Co 2 P/CNTs, 44 CoFe 2 O 4 /MWCNTs, 45 Ni–Fe, 46 FeNiP@N-CFs, 47 NiCo 2 O 4 @NiMo 2 S 4 , 48 CoP/NCNHP, 49 Ni–Co–Se/CFP, 50 Fe 2 Ni 2 N/rGO 51 and CNTs@CoS x Se 2(1− x ) (Fig. 4c).…”

Coconut-Water-Mediated Carbonaceous Electrode: A Promising Eco-Friendly Material for Bifunctional Water Splitting Application

“…However, owing to the high cost and scarcity, they are obstructed. 7 Researchers have made several efforts to develop nonprecious metal-based catalysts for water splitting such as from sulfides, 8 selenides, 9 oxides, 10 etc. Among the known catalysts, carbon/carbonaceous electrode materials have demonstrated an excellent chemical and mechanical stability and porosity, high surface area, fine-controlled pore coordination, i.e., pore-size distribution and connectivity, good conductivity, low cost, and stability.…”