MOF-Derived Co₃S₄ Nanoparticles Embedded in Nitrogen-Doped Carbon for Electrochemical Oxygen Production

Abstract

The development of a simple and effective strategy for designing a highly efficient oxygen evolution electrocatalyst is more important to speed up the efficiency-limiting step involved in water electrolysis. The high efficiency of the oxygen evolution reaction (OER) is directly correlated with the class of electrode materials employed. This work reports a series of Co3S4 nanoparticles (Co3S4-2h, Co3S4-3h, and Co3S4-4h) derived from a metal–organic framework (MOF) via a single-step annealing strategy with varying reaction times for the study of OER. During the annealing process, the MOF precursor [Co3(tiron-bpy)2(bpy)(H2O)8]·(H2O)2 termed as Co-T-BPY directly converted to cobalt sulfide (Co3S4) nanoparticles, along with additional support of the N-doped carbon moiety. Interestingly, variation of reaction time in a fixed temperature condition played a decisive role in optimizing the surface area with huge active sites of the derived products. The optimized Co3S4-3h product needed an overpotential of 285 mV to reach 10 mA cm–2 current density and an acceptable Tafel value (109 mV dec–1) with excellent 14 h of stability performance under harsh alkaline conditions. The OER results are attributed to the combined effect of the Co3S4 phase and N-doped carbon matrix, resulting in substantial stability and high conductivity. Therefore, we believe that the time variation strategy for the preparation of a cobalt-based non-precious electrode material can pave the way in search of an OER-efficient electrocatalyst.

Low-temperature synthesis of high-entropy amorphous metal oxides (HEOs) for enhanced oxygen evolution performance

“…41,42,46,47 Herein, the HEO-110 electrode material shows a lower R ct value in comparison to other ones, implying faster charge transfer kinetics for enhanced OER activity. 14 Moreover, long-term stability performance tests (chronopotentiometry) were carried out to verify the practical usability of the OER active HEO-110 electrode material at a constant 10 mA cm −2 , as illustrated in Fig. 5d.…”

“…The Tafel equation is represented as η = a + b log J (where η = overpotential, a = intercept, b = Tafel slope, and J = current density). 4,14 The electrochemical impedance spectroscopy (EIS) study was recorded at 1.52 V in an applied frequency of 100 kHz to 0.01 Hz, followed by an AC amplitude of 5 mV s −1 . Moreover, the electrochemical active surface area (ECSA) of the as-synthesized material was calculated from double-layer capacitance ( C dl ), estimated from the non-faradaic portion of the cyclic voltammetry curve at different scan values (10–200 mV s −1 ).…”

“…7–11 In addition, more research concentrates on the synthesis of metal–organic frameworks (MOFs) and their derived electrode material used as the superior electrocatalyst for the generation of molecular oxygen (O 2 ) in an alkaline medium. 12–14 However, the electrochemical performances still need to be refined in the search for advanced electrocatalysts to solve the energy problem. Recently, high-entropy materials (HEMs) have been used as a new class of electrode material for electrocatalytic applications due to their synergistic effect of five or multi-metallic elements, good electrical conductivity, high-entropy effects, and structural stability.…”

Co- and V2O3-Modified Ni-Based Nanocatalyst for 5-Hydroxymethylfurfural Electrooxidation

“…These results confirm the promoting effects of Co and V 2 O 3 . In addition, Co–Ni/V 2 O 3 /NF exhibits the smallest Tafel slope and charge transfer resistance than other samples (Figure S6b,c), indicating its fast reaction kinetics and charge transfer during HMFOR. , Moreover, the electrochemical surface area (ECSA) of the catalyst is evaluated by the electrochemical double-layer capacitance ( C dl ) from CV curves in the nonfaradaic potential. , Co–Ni/V 2 O 3 /NF exhibits the largest ECSA value, illustrating that it exposes more effective sites for HMFOR (Figure S6d,e). The corresponding ECSA-normalized LSV curves provide insights into its higher intrinsic HMFOR activity (Figure S6f).…”