Electronegativity‐Induced Charge Balancing to Boost Stability and Activity of Amorphous Electrocatalysts

Abstract

due to the largely increased number of active sites and more effective dangling bonds/defects. Despites these flashing points, the poor crystallinity and defective structure in amorphous materials often lead to the high solubility and low stability in aqueous solution, [7] and thus limit the practical utilization of amorphous catalysts. Therefore, it is needed to develop efficient strategies to stabilize amorphous catalysts.Molybdenum oxysulfide (MoS x O y ) as a potential hydrogen evolution reaction (HER) catalyst overcomes the in-plane inertness and low conductivity of molybdenum disulfide due to the highly active Mo-oxo and metallic nature of molybdenum oxides. [7,8] However, amorphization induces obvious degradation of stability in oxygen-containing molybdenum compounds due to their high solubility in aqueous electrolyte to form molybdic acid. [9] Two strategies are employed to solve this critical issue: one is to coat a thin layer of catalysts to a substrate (e.g., graphene) with the bridging group to strengthen the interaction between catalysts and substrate; [10] the other method is to convert unstable phases/structures to aqueous solution-resistant ones. [11] Although these attempts can enhance the stability to a certain extent, a balanced strategy to simultaneously maintain the active species/structure and enhance the stability remains not yet achieved. Amorphization is an efficient strategy to activate intrinsically inert catalysts. However, the low crystallinity of amorphous catalysts often causes highsolubility and poor electrochemical stability in aqueous solution. Here, a different mechanism is developed to simultaneously stabilize and activate the water-soluble amorphous MoS x O y via a charge-balancing strategy, which is induced by different electronegativity between the co-dopants Rh (2.28) and Sn (1.96). The electron-rich Sn prefers to stabilize the unstable apical O sites in MoS x O y through charge transfer, which can prevent the H from attacking. Meanwhile, the Rh, as the charge regulator, shifts the main active sites on the basal plane from inert Sn to active apical Rh sites. As a result, the amorphous RhSn-MoS x O y exhibits drastic enhancement in electrochemical stability (η 10 increases only by 12 mV) after 1000 cycles and a distinct activity (η 10 : 26 mV and Tafel: 30.8 mV dec −1 ) for the hydrogen evolution reaction in acidic solution. This work paves a route for turning impracticably water-soluble catalysts into treasure and inspires new ideas to design high-performance amorphous electrocatalysts.

Novel (Pt‐Ox)‐(Co‐Oy) Nonbonding Active Structures on Defective Carbon from Oxygen‐Rich Coal Tar Pitch for Efficient HER and ORR

“…On the other hand, highly electronegative O atom will induce the accelerated electron transfer from Pt to O. [31,32] The reduced central charge density of Pt and the nearly empty d 2 z orbital are unfavorable to the electronic interaction between Pt and the reaction intermediates. [29,[33][34][35] The reconstruction of Pt-O x local electronic state may be an effective strategy to balance the charge distribution.…”

Amorphization of LaCoO3 Perovskite Nanostructures for Efficient Oxygen Evolution

“…In addition, the double-layer capacitance (C dl ) experiments were performed to evaluate the electrochemically active surface area (ECSA) of the synthesized catalysts (Figure S7), where a large value of C dl demonstrates an increased active surface and numbers of stored protons. 37 Calculating from the cyclic voltammetry (CV) operations, the value of C dl of LaCoO 3 −Reduce is 10.83 mF, which is substantially higher than that of LaCoO 3 − Pristine (Figure S8). It is impressive that the ECSA of the LaCoO 3 −Reduce was 5.7-fold more than that of the LaCoO 3 − Pristine (Figure S9).…”

“…Moreover, the Tafel slope of LaCoO 3 –Reduce (63.4 mV dec –1 ) is much smaller than that of LaCoO 3 –Pristine (96.6 mV dec –1 ) and commercial IrO 2 (80.3 mV dec –1 ), indicating that the amorphous LaCoO 3 –Reduce demonstrates faster reaction kinetics for OER than that of the crystallized LaCoO 3 –Pristine (Figure b). In addition, the double-layer capacitance ( C dl ) experiments were performed to evaluate the electrochemically active surface area (ECSA) of the synthesized catalysts (Figure S7), where a large value of C dl demonstrates an increased active surface and numbers of stored protons . Calculating from the cyclic voltammetry (CV) operations, the value of C dl of LaCoO 3 –Reduce is 10.83 mF, which is substantially higher than that of LaCoO 3 –Pristine (Figure S8).…”

Unveiling the Accelerated Water Electrolysis Kinetics of Heterostructural Iron‐Cobalt‐Nickel Sulfides by Probing into Crystalline/Amorphous Interfaces in Stepwise Catalytic Reactions

“…The stability results confirmed that a high percentage of crystalline in the nanomaterial favors long‐term stability of the catalyst, and the stability of FeCo(NiS 2 ) 4 ‐C/A at a higher current density is stronger than that at a lower current density. [ 16 , 38 ]…”

“…The stability results confirmed that a high percentage of crystalline in the nanomaterial favors long-term stability of the catalyst, and the stability of FeCo(NiS 2 ) 4 -C/A at a higher current density is stronger than that at a lower current density. [16,38] Single FeCo(NiS 2 ) 4 -C/A electrode bifunctionally catalyzing both HER and OER could greatly simplify the water splitting system and reduce the production cost. Encouraged by the impressive catalytic activity of the FeCo(NiS 2 ) 4 -C/A in terms of both HER and OER, we then assembled a water electrolyzer employing the FeCo(NiS 2 ) 4 -C/A as anode and cathode for overall water splitting test in 1 M KOH.…”