Nickel selenide/g-C3N4 heterojunction photocatalyst promotes CC coupling for photocatalytic CO2 reduction to ethane

Photocatalytic CO2 reduction to generate high value-added and renewable chemicals is of great potential in facilitating the realization of closed-loop and carbon-neutral hydrogen economy. Stabilizing and accelerating the formation of COCO* intermediate is crucial to achieve high-selectivity ethane production. Herein, a novel 3D/2D NiSe2/g-C3N4 heterostructure that mesoscale hedgehog nickel selenide (NiSe2) grown on the ultrathin g-C3N4 nanosheets were synthesized via a successively high temperature calcination process and in-situ thermal injection method for the first time. The optimum 2.7 % NiSe2/g-C3N4 heterostructure achieved moderate C2H6 generation rate of 46.1 μmol·g-1·h-1 and selectivity of 97.5 % without any additional photosensitizers and sacrificial agents under light illumination. Based on the results of the theoretical calculations and experiments, the improvement of photocatalytic CO2 to C2H6 production and selectivity should be ascribed to the increased visible light absorption ability, unique 3D/2D heterostructures with promoted adsorption of CO2 molecules on the Ni active sites, the type II heterojunction with improved charge transfer dynamics and lowered interfacial transfer resistance, as well as the formation of COCO* key intermediate. This work provides an inspiration to construct efficient photocatalysts for the direct transformation of CO2 to multicarbon products (C2+).

Hollow carbon spheres loaded with NiSe2 nanoplates as multifunctional SeS2 hosts for Li-SeS2 batteries

Selenium sulfide as a new alternative cathode material can effectively address the inferior electronic conductivity of sulfur, which is the main cause for poor electrochemical reactivity of conventional lithium-sulfur batteries (Li-S batteries). Therefore, in this work, hollow carbon spheres loaded with NiSe₂ nanoplates were prepared as SeS₂ hosts for Li-SeS₂ batteries. The unique micro-mesoporous hollow carbon spheres not only provide channels for the diffusion of SeS₂, but also afford spaces for alleviating the volume expansion of the active substance. Besides, the external polar NiSe₂ nanoplates increase active sites for capturing polysulfides or polyselenides during the charge/discharge process. Meanwhile, the excellent electronic conductivity of NiSe₂ can accelerate the catalytic reaction on the surface, thus reducing the loss of soluble intermediate products and finally suppressing the "shuttle effect". These extraordinary features of the as-proposed cathode offer many superiorities in electrochemical performances in terms of a high initial discharge capacity of 1139 mA h g^-1 at a current rate of 0.1C and an excellent cycling life of up to 1000 cycles at 1C.

Phosphorus doped nickel selenide for full device water splitting

The lack of high active and stable electrocatalysts has impeded the development of electrochemical water splitting device, which is promising technique for renewable energy conversion system. Here, we report a one-step protocol to synthesize P doped NiSe₂ (P-NiSe₂) by selenylation process derived from nickel foam with assistant of NaH₂PO₂ and Se powder. The P-NiSe₂ could be directly used as working electrode and shows the superior electrochemical activity, offering current density of 10 mA cm^-2 with overpotential of 270 mV for OER and 71 mV for HER. The enhanced electrochemical activity can be ascribed to the P atom doping. The P atom doping leads to the high valence state of Ni active sites, which have high catalytic ability towards OER. Moreover, the P doping makes the d-band center of Ni atoms in P-NiSe₂ move close to Fermi level, facilitating the HER kinetics with respect to proton adsorption and hydrogen desorption. When employed P-NiSe₂ as both anodic and cathodic electrode in alkaline water electrolyzer, a current density of 10 mA cm^-2 can be achieved at 1.58 V. Our work highlights the importance of P doping in determining the surface electron configuration for full device water splitting and the facile synthesis protocol would be promising for realistic applications.

Two-dimensional metal chalcogenides analogous NiSe2 nanosheets and its efficient electrocatalytic performance towards glucose sensing

Recently, 2D layered transition-metal dichalcogenide materials have received great consideration because of their unique electronic properties, large surface area and high electrocatalytic activity. In this connection, for the first time the similar nanostructured material of NiSe₂ nanosheets (NiSe₂-NS) has been synthesized by a facile hydrothermal method for electrocatalytic applications. Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), X-ray Photoelectron Spectroscopy (XPS), Energy Dispersive X-ray analysis (EDX), X-ray diffraction spectrum (XRD) results confirmed the formation of NiSe₂-NS with required stoichiometry and morphology. Electrochemical Impedance Spectroscopy (EIS) data indicate that electron transfer is facile at the NiSe₂-NS modified glassy carbon electrode (GCE). It has been as an electrode modifier for glucose sensing applications. The electrochemical studies were performed for NiSe₂-NS modified GCE using Cyclic Voltammetry (CV) and amperometric i-t techniques. The results are suggesting the effective response of NiSe₂-NS/GCE with a very low limit of detection (LOD) and sensitivity of 23nM and 5.6μAμM^-1cm^-2 respectively. Moreover, the selectivity data exhibited excellent anti-interference property of NiSe₂-NS/GCE towards glucose in the presence of possible interfering agents viz. Ascorbic acid, dopamine, glucose.