FeNi2P three-dimensional oriented nanosheet array bifunctional catalysts with better full water splitting performance than the full noble metal catalysts

Iron-Nickel synergistic catalysis growth of (Fe,Ni)9S8/Ni3S2@N,S codoped carbon bridged nanowires enhanced oxygen evolution reaction performance

Improving the conductivity of the electrocatalyst itself is essential for enhancing its performance. In this work, N, S-rich 6-thioguanine (TG) is selected as the ligand to synthesize a Fe, Ni bimetallic porous coordination polymer (PCP), which is then derived to fabricate N,S codoped carbon (NSC)-coated (Fe,Ni)9S8/Ni3S2 bridged nanowires. The (Fe,Ni)9S8/Ni3S2@NSC bridged nanowires obtained through bimetallic synergistic catalysis and self-sulfurization processes not only introduced additional electrocatalytic active sites but also significantly enhance the overall conductivity of the catalyst due to the interconnected nanowire structure. The resulting (Fe,Ni)9S8/Ni3S2@NSC demonstrates remarkable oxygen evolution reaction (OER) performance, exhibiting an overpotential as low as 252 mV at a current density of 10 mA cm-2. This work proposes a novel strategy for enhancing the overall conductivity of catalysts by growing bridged nanowires, providing valuable insights and inspiration for the design and preparation of advanced transition metal sulfide electrocatalysts.

NiFe-layered double hydroxide/CoP2@MnP heterostructures of clustered flower nanowires on MXene-modified nickel foam for overall water-splitting

Exploiting efficient and economical electrocatalysts is indispensable to promoting the sluggish kinetics of overall water-splitting. Herein, we designed a phosphate reaction and two-step hydrothermal method to construct a 3D porous clustered flower-like heterogeneous structure of NiFe-layered double hydroxide (NiFe) and CoP2@MnP (CMP) grown in-situ on MXene-modified nickel foam (NF) substrate (denoted as NiFe/CMP/MX), with favorable kinetics. Density functional theory calculations (DFT) demonstrate that the self-driven transfer of heterojunction charges causes electron redistribution of the catalyst, and optimizes the electron transfer rate of the active site and the d-band center near the Fermi level, thereby reducing the adsorption energy of H and O reaction intermediates (H*, OH*, OOH*). As expected, the combination of CMP and NiFe with naturally conductive MXene forms a strong chemical and electron synergistic effect, which enables the synthesized NiFe/CMP/MX heterogeneous structure exhibits good activity for oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) with a low overpotential of 200 mV and 126 mV at 10 mA cm-2, respectively. Furthermore, the overpotential of 1.58 V is enough to drive a current density of 10 mA cm-2 in a two-electrode configuration, which is better than noble metals (RuO2(+)//Pt/C(-)) (1.68 V).

Investigation of polyethylene glycol (PEG) assisted solvothermal synthesis of CuCoO2 nanosheets for efficient oxygen evolution reaction

Water splitting to produce hydrogen is known as an effective way to alleviate the energy crisis, but the slow kinetics of the oxygen evolution reaction (OER) has been seriously restricting the development of water splitting technology. Therefore, low cost and high efficiency OER electrocatalysts have become substitutes for traditional noble metal-based catalysts. In this work, CuCoO2 nanosheets (denoted by CCO2) were successfully synthesized under the regulation of surfactants and a solvent polyethylene glycol (PEG) by a solvothermal route using Cu-BTC and Co(NO3)2·6H2O as reactants. The experimental results confirmed that PEG addition could further reduce significantly the crystal size of the CCO2 nanosheets, i.e., the size was about 150 nm and the thickness was 13 nm. The Ni@CCO2 electrode exhibits outstanding OER performance in 1.0 M KOH electrolyte, which shows the overpotential at 10 mA cm-2 is 378 mV, and the Tafel slope is 85 mV dec-1. Moreover, the CCO2 nanosheets exhibit good structural and compositional stability after the 18 h constant current OER test. Therefore, this work may offer a novel insight into enhancing the OER performance of CuCoO2 catalysts by decreasing their crystal size, and using a solvothermal route.

Reconstruction of CoNx /NC Catalyst during Oxygen Evolution Reaction by Fe3+ Modulation for Enhanced Activity and Stability

The surface reconstruction of transition metal-based catalysts has been demonstrated to be beneficial for oxygen evolution reaction (OER). However, regulating the activity and stability of the components derived from reconstruction is challenging. Here, a strategy of Fe3+ ion modulating the reconstruction components of CoN0.4 on a nitrogen-doped carbon carrier(CoN0.4 /NC) electrocatalyst for promoted OER activity and stability is reported. During the OER process, the cobalt nitride components on the surface of CoN0.4 /NC catalyst were converted into CoOOH and Co4+ species. The addition of Fe3+ stabilized the CoOOH phase and facilitated the formation of Fe-CoOOH active phase, enhancing the activity and stability of CoN0.4 /NC. The Fe10 -CoN0.4 /NC catalyst achieved a current density of 10 mA cm-2 at a low overpotential of 300 mV (vs. RHE) with a Tafel slope of 68.12 mV dec-1 . The overpotential of Fe10 -CoN0.4 /NC was 122 mV lower than that of the CoN0.4 /NC catalyst and was comparable to commercial RuO2 catalyst. This study develops a novel technology for regulating the production of reconstructed species using Fe3+ ions.

Structural engineering and electronic state tuning optimization of molybdenum-doped cobalt hydroxide nanosheet self-assembled hierarchical microtubules for efficient electrocatalytic oxygen evolution

Cobalt-based hydroxide are ideal candidates for the oxygen evolution reaction. Herein, we use molybdenum oxide nanorods as sacrificial templates to construct a self-supporting molybdenum-doped cobalt hydroxide nanosheet hierarchical microtubule structure based on a structural engineering strategy to improve the active area of the catalyst. X-ray-based spectroscopic tests revealed that Mo (VI) with tetrahedral coordination intercalated into the interlayer of cobalt hydroxide, promoting interlayer separation. At the same time, Mo is connected with Co through oxygen bonds, which promotes the transfer of Co charges to Mo and reduces the electron cloud density of Co ions. In 1 M KOH, optimized molybdenum-doped cobalt hydroxide nanosheet microtubules only needs an overpotential of 288 mV to drive a current density of 10 mA cm^-2, which is significantly better than that of pure Co(OH)₂ nanosheets and RuO₂. Structural engineering and electronic state regulation can effectively improve the oxygen evolution activity of cobalt-based hydroxide, which provides a design idea for the development of efficient oxygen evolution catalysts.