Arousing the Reactive Fe Sites in Pyrite (FeS₂) via Integration of Electronic Structure Reconfiguration and in Situ Electrochemical Topotactic Transformation for Highly Efficient Oxygen Evolution Reaction

Abstract

Despite significant advances in the development of highly efficient and robust oxygen evolution reaction (OER) electrocatalysts to replace noble-metal catalysts, commercializing OER catalysts with high catalytic activity for sustainable development still remains a great challenge. Especially, transition-metal Fe-based OER catalysts, despite their earth-abundant, cost-efficient, and environmentally benign superiorities over Co-and Ni-based materials, have received relatively insufficient attention because of their poor apparent OER activities. Herein, by rational design, we report Ni-modified pyrite (FeS 2 ) spheres with yolk−shell structure that could serve as pre-electrocatalyst precursors to induce a highly active nickel−iron oxyhydroxide via in situ electrochemical topological transformation under the OER process. Notably, as confirmed by the results of X-ray absorption spectroscopy, X-ray photoelectron spectroscopy, and density functional theory (DFT) calculations, Ni doping could effectively regulate the intrinsic electronic structure of FeS 2 to realize a semiconductor-to-semimetal transition, which endows FeS 2 with dramatically improved conductivity and water adsorption ability, providing prequisites for subsequent topological transformation. Moreover, systematic post-characterizations further reveal that the optimal Ni-FeS 2 -0.5 sample completely converts to amorphous Nidoped FeOOH via an in situ electrochemical transformation with yolk−shell structure well-preserved under the OER conditions. The electronic structure modulation combined with electrochemical topotactic transformation strategies well stimulate the reactive Fe sites in Ni-FeS 2 -0.5, which show impressively low overpotentials of 250 and 326 mV to drive the current densities (j) of 10 and 100 mA cm −2 , respectively, and a Tafel slope as small as 34 mV dec −1 for the OER process. When assembled as a water electrolyzer for the overall water splitting, Ni-FeS 2 -0.5 can display a low voltage of 1.55 V to drive a current density of 10 mA cm −2 , outperforming most of the transition-metal-based bifunctional electrocatalysts to date. This work may provide new insight into the rational design of other high-performance Fe-based OER electrocatalysts and inspire the exploration of cost-effective, ecofriendly electrocatalysts to meet the demand for future sustainable development.

FeS2/C Nanowires as an Effective Catalyst for Oxygen Evolution Reaction by Electrolytic Water Splitting

“…The early onset and the large anodic current of all samples indicate their high OER catalytic activity. Figure 6a shows that the working electrode has a good catalytic activity for OER at the first cycle, which is better than the pure iron sulfides without doping other metal ions reported before [19]. The porous structure provides more sites for the OER reaction, and the encapsulation of carbon enhances the conductivity of the catalyst toward a fast electron transfer.…”

“…The less active sites and intrinsically low electrical conductivity of Fe-based catalysts cause the lower activity of the OER process. Recently, however, many reports demonstrated that Fe is also a good candidate for the active site towards OER [10,18,19]. Operando X-ray absorption spectroscopy was used by Bell and co-workers to study OER over nickel–iron oxyhydroxides [20].…”

Anchoring stable FeS2 nanoparticles on MXene nanosheets via interface engineering for efficient water splitting

“…The broad shoulder peaks at about 711.0 and 724.9 eV belong to the satellite peaks. 24,48 Additionally, the peaks positively shift compared with those of pristine FeS 2 , suggesting that the modified electronic structure of Fe is due to robust electronic interactions between FeS 2 and MXene. In the S 2p spectrum (Fig.…”

Unraveling the Beneficial Microstructure Evolution in Pyrite for Boosted Lithium Storage Performance

“…[37,39] Furthermore, the shoulder peak (the inset in Figure 2d Figure S8 in the Supporting Information), and corresponding crystal structure parameters were obtained (Table S2 in the Supporting Information). [28,39] The strong peaks in the range 1-3 in Figure 2f,i correspond to FeÀSb onding and MoÀSb onding, respectively.A sc learly shown in Ta ble S2 (in the SupportingI nformation), the coordination number of the FeÀSb onding for FeS 2 /MoS 2 decreases from 6t o5 .5 in comparison with the pristine FeS 2 ,a nd this result may be caused by the disordered and defective interfaces, which could provide more active sites for lithium storage. [40] Moreover,t he MoÀSb ondingf or FeS 2 /MoS 2 also decreasesi ni ts coordination number (from 6t o5 .6), which is consistentw ith the phenomenon observed from the FeÀS bonding.…”