Janus electronic state of supported iridium nanoclusters for sustainable alkaline water electrolysis.

Metal-support electronic interactions play crucial roles in triggering the hydrogen spillover (HSo) to boost hydrogen evolution reaction (HER). It requires the supported metal of electron-rich state to facilitate the proton adsorption/spillover. However, this electron-rich metal state contradicts the traditional metal→support electron transfer protocol and is not compatible with the electron-donating oxygen evolution reaction (OER), especially in proton-poor alkaline conditions. Here we profile an Ir/NiPS3 support structure to study the Ir electronic states and performances in HSo/OER-integrated alkaline water electrolysis. The supported Ir is evidenced with Janus electron-rich and electron-poor states at the tip and interface regions to respectively facilitate the HSo and OER processes. Resultantly, the water electrolysis (WE) is efficiently implemented with 1.51 V at 10 mA cm-2 for 1000 h in 1 M KOH and 1.44 V in urea-KOH electrolyte. This research clarifies the Janus electronic state as fundamental in rationalizing efficient metal-support WE catalysts.

Enlarging the Ni-O Bond Polarizability in a Phosphorene-Hosted Metal-Organic Framework for Boosted Water Oxidation Electrocatalysis.

The emerging lattice-oxygen oxidation mechanism (LOM) presents attractive opportunities for breaking the scaling relationship to boost oxygen evolution reaction (OER) with the direct OLattice-*O interaction. However, currently the LOM-triggering rationales are still debated, and a streamlined physicochemical paradigm is extremely desirable for the design of LOM-defined OER catalysts. Herein, a Ni metal-organic framework/black phosphorene (NiMOF/BP) heterostructure is theoretically profiled and constructed as a catalytic platform for the LOM-derived OER studies. It is found that the p-type BP host can enlarge the Ni-O bond polarizability of NiMOF through the Ni-O bond stretching and Ni valence declining synergically. Such an enlarged bond polarizability will in principle alleviate the lattice oxygen confinement to benefit the LOM pathway and OER performance. As a result, the optimized NiMOF/BP catalyst exhibits promising OER performance with a low overpotential of 260 mV at 10 mA cm-2 and long-term stability in 1 M KOH electrolyte. Both experiment and calculation results suggest the activated LOM pathway with a more balanced step barrier in the NiMOF/BP OER catalyst. This research puts forward Ni-O bond polarizability as the criterion to design LOM-scaled electrocatalysts for water oxidation.

Macroporous SnO2/MoS2 inverse opal hierarchitecture for highly efficient trace NO2 gas sensing.

The innovation of NO2 gas sensors is highly desirable in environmental monitoring and human safety. Herein, a macroporous SnO2/MoS2 inverse opal hierarchitecture has been constructed with substantial interface charge transfer, which realizes the efficient and stable detection of NO2 with an enhanced response, fast kinetics, and high selectivity at low temperatures.

Synergizing Hydrogen Spillover and Deprotonation by the Internal Polarization Field in a MoS2 /NiPS3 Vertical Heterostructure for Boosted Water Electrolysis.

Hydrogen spillover (HSo) has emerged to upgrade the hydrogen evolution reaction (HER) activity of Pt-support electrocatalysts, but it is not applicable to the deprotonated oxygen evolution reaction (OER). Non-precious catalysts that can perform well in both HSo and deprotonation (DeP) are extremely desirable for a sustainable hydrogen economy. Herein, an affordable MoS2 /NiPS3 vertical heterostructure catalyst is presented to synergize HSo and DeP for efficient water electrolysis. The internal polarization field (IPF) is clarified as the driving force of HSo in HER electrocatalysis. The HSo from the MoS2 edge to NiPS3 can activate the NiPS3 basal plane to boost the HER activity of the MoS2 /NiPS3 heterostructure (112 mV vs reversible hydrogen electrode (RHE) at 10 mA cm-2 ), while for OER, the IPF in the heterostructure can facilitate the hydroxyl diffusion and render MoS2 -to-NiPS3 /P-to-S dual-pathways for DeP. As a result, the stacking of OER-inactive MoS2 on the NiPS3 surface still brings intriguing OER enhancements. With them serving as electrode couples, the overall water splitting is attested stably with a cell voltage of 1.64 V at 10 mA cm-2 . This research puts forward the IPF as the criterion in the rational design of HSo/DeP-unified non-precious catalysts for efficient water electrolysis.

Shining Light on Anion-Mixed Nanocatalysts for Efficient Water Electrolysis: Fundamentals, Progress, and Perspectives.

HIGHLIGHTS: This review introduces recent advances of various anion-mixed transition metal compounds (e.g., nitrides, halides, phosphides, chalcogenides, (oxy)hydroxides, and borides) for efficient water electrolysis applications in detail. The challenges and future perspectives are proposed and analyzed for the anion-mixed water dissociation catalysts, including polyanion-mixed and metal-free catalyst, progressive synthesis strategies, advanced in situ characterizations, and atomic level structure-activity relationship. Hydrogen with high energy density and zero carbon emission is widely acknowledged as the most promising candidate toward world's carbon neutrality and future sustainable eco-society. Water-splitting is a constructive technology for unpolluted and high-purity H2 production, and a series of non-precious electrocatalysts have been developed over the past decade. To further improve the catalytic activities, metal doping is always adopted to modulate the 3d-electronic configuration and electron-donating/accepting (e-DA) properties, while for anion doping, the electronegativity variations among different non-metal elements would also bring some potential in the modulations of e-DA and metal valence for tuning the performances. In this review, we summarize the recent developments of the many different anion-mixed transition metal compounds (e.g., nitrides, halides, phosphides, chalcogenides, oxyhydroxides, and borides/borates) for efficient water electrolysis applications. First, we have introduced the general information of water-splitting and the description of anion-mixed electrocatalysts and highlighted their complementary functions of mixed anions. Furthermore, some latest advances of anion-mixed compounds are also categorized for hydrogen and oxygen evolution electrocatalysis. The rationales behind their enhanced electrochemical performances are discussed. Last but not least, the challenges and future perspectives are briefly proposed for the anion-mixed water dissociation catalysts.

Amorphous materials for elementary-gas-involved electrocatalysis: an overview.

Given the critical demands on energy conversion, storage, and transportation, tremendous interest has been devoted to the field of material development related to energy harvesting, recently. As the only route towards energy utilization, the carriers with the characteristics of low carbon are regarded as the future choice, e.g., hydrogen and ammonia. To this end, electrocatalysis provides a green way to access these substances. However, the unfulfilled conversion efficiency is the bottleneck for practical application. In this review, the promising characteristics of amorphous materials and the amorphous-induced electrocatalytic enhancement (AIEE) were emphasized. In the beginning, the characteristics of amorphous materials are briefly summarized. The basic mechanism of heterogeneous electrocatalytic reactions is illustrated, including the hydrogen/oxygen evolution and oxygen/nitrogen reduction. In the third part, the electrocatalytic performance of amorphous materials is discussed in detail, and the mechanism of AIEE is highlighted. In the last section of this review, the challenges and outlook for the development of amorphous enhanced electrocatalysis are presented.

Quenching-Induced Structural Distortion of Graphitic Carbon Nitride Nanostructures: Enhanced Photocatalytic Activity and Electrochemical Hydrogen Production.

Engineered nanomaterials are emerging in the field of environmental chemistry. This study involves the analysis of the structural, electronic, crystallinity, and morphological changes in graphitic carbon nitride (g-C3N4), an engineered nanomaterial, under rapid cooling conditions. X-ray diffraction, scanning electron microscopy, high-resolution transmission electron microscopy, Brunauer-Emmett-Teller, Fourier transform infrared, Raman, band gap, and Mott-Schottky analyses strongly proved that the liquid N2-quenched sample of g-C3N4 has structural distortion. The photocatalytic efficiency of engineered g-C3N4 nanostructures was analyzed through the degradation of reactive red 120 (RR120), methylene blue (MB), rhodamine B, and bromophenol as a representative dye. The photocatalytic dye degradation efficiency was analyzed by UV-vis spectroscopy and total organic carbon (TOC) analysis. The photocatalytic efficiency of g-C3N4 under different quenching conditions included quenching at room temperature in ice and liquid N2. The degradation efficiencies are found to be 4.2, 14.7, and 82.33% for room-temperature, ice, and liquid N2 conditions, respectively. The pseudo-first-order reaction rate of N2-quenched g-C3N4 is 9 times greater than the ice-quenched g-C3N4. Further, the TOC analysis showed that 55% (MB) and 59% (RR120) of photocatalytic mineralization were achieved within a time duration of 120 min by the liquid N2-quenched g-C3N4 nanostructure. In addition, the quenched g-C3N4 electrocatalytic behavior was examined via the hydrogen (H2) evolution reaction in acidic medium. The liquid N2-quenched g-C3N4 catalyst showed a lower overpotential with high H2 evolution when compared with the other two g-C3N4-quenched samples. The results obtained provide an insight and extend the scope for the application of engineered g-C3N4 nanostructures in the degradation of organic pollutants as well as for H2 evolution.

Effect of peroxomonosulfate, peroxodisulfate and hydrogen peroxide on graphene oxide photocatalytic performances in methyl orange dye degradation.

Carbocatalyst GO photocatalytic mechanism and performances in the presence of an electron scavenger (ES) has been consciously discussed herein. Single layer GO photocatalyst has been synthesized by Hummer's method and photocatalyst characteristics are gathered by different analytical methods. Studies ensured the formation of a good crystalline GO that contains number of oxygenated functional groups, with average crystalline size of the sp2 domain in 18.24 nm. Optical studies suggest that optical band gap of the GO nanosheet photocatalyst is found in the range of 3.19-4.4 eV. TEM analysis confirms the formation of a single layer GO nanosheet. Photocatalytic study justifies that in the absence of ES, 24% mineralization efficiency is achieved with GO as a photocatalyst, whereas in the presence of ES such as PMS, PDS and HP the mineralization efficiency is considerably enhanced up to 91%, 77% and 65% respectively. Moreover, photocatalytic degradation intermediate byproducts were also examined through LC-MS analysis. The study substantiates methyl orange dye degradation undergoes via the multiple degradation pathway such as (i) azo bond cleavage and hydroxylation, (ii), asymmetric cleavage followed by reduction of sulfonate group and aromatic ring removal and (iii) consecutive demethylation reactions and sulfonate group removal. Rationalized the contributing effects of process parameters towards the photocatalytic degradation of methyl orange using a RSM based on CCD validation. The validation reveals that most significant process parameter affects degradation process are the irradiation time, catalyst loading and choice of ES.

Novel high-efficiency Eu3+-activated Na2Gd2B2O7 red-emitting phosphors with high color purity.

In this study, a series of Na2(Gd1-x Eu x )2B2O7 (abbreviated as: Na2Gd2B2O7:xEu3+; x = 0, 0.05, 0.15, 0.35, 0.45, and 0.50) phosphors were synthesized by conventional solid state reaction approach. The structure and morphology of the as-prepared phosphors were studied by X-ray diffraction, scanning electron microscopy and elemental mapping. The results indicated that the phosphors had micro-size particles with monoclinic phases. The photoluminescence excitation and emission study indicated that the as-prepared phosphors could give rise to efficient red emissions under near-ultraviolet excitation. The optimal doping concentration of Eu3+ ions was x = 0.35, and the corresponding deduced critical distance (R c) was about 9.4 Å. The concentration quenching mechanism was dominated by energy-transfer among the Eu3+ ions through dipole-dipole interactions. The calculated internal quantum efficiency of the Na2Gd2B2O7:0.35Eu3+ red phosphor was 70.8% and the color purity was as high as 99%. Furthermore, decay dynamics revealed that with the increase in the content of Eu3+, the lifetimes decreased due to the increase in non-radiative transition. Importantly, the present Na2Gd2B2O7:0.35Eu3+ phosphors also exhibited good thermal stability, and the emission intensity at 150 °C was about 56% of that at 30 °C. Furthermore, a warm white light-emitting diode (WLED) device was fabricated with commercial BaMgAl10O17:Eu2+ blue phosphors, (Ba,Sr)2(SiO4):Eu2+ green phosphors, and the as-prepared Na2Gd2B2O7:0.35Eu3+ red phosphors as well as a 395 nm LED chip. The device exhibited CIE coordinates of (0.4367, 0.3987), a high color rendering index (CRI = 92.2), a low correlated color temperature (CCT = 2960 K), and a luminous efficacy of 40.65 lm W-1. The observed results strongly indicate that the as-prepared Na2Gd2B2O7:Eu3+ phosphors may be used as the red emitting component in pc-WLEDs.