Electrochemical activation-induced Co-Ni-Mo-O nanosheets with low crystallinity and abundant active sites for efficient and ultra-stable hydrogen generation.

Co/Ni/Mo-based oxides are promising candidates for the hydrogen evolution reaction (HER). However, these electrocatalysts often exhibit unsatisfactory HER performance due to the lack of active sites. Herein, an in situ electrochemical activation strategy is proposed to modify the surface structure of a Co-Ni-Mo-O catalyst. During the HER in an alkaline electrolyte, the Co-Ni-Mo-O nanosheets display an activation period and a rough layer with low crystallinity is then formed on the surface of Co-Ni-Mo-O nanosheets with the leaching of partial Mo species. Owing to the synergistic catalysis of multiple metal components, a large electrochemically active surface area provided by the rough surface, and fully exposed active sites in the low-crystalline structure, the activated Co-Ni-Mo-O/NF shows favorable HER activity with an overpotential of only 42 mV at -10 mA cm-2. Furthermore, it remains stable at a large current density of -250 mA cm-2 for more than 400 h, outperforming almost all the oxide-based electrocatalysts. Such an electrochemical reduction activation strategy provides a feasible way for the surface modification and targeted design of advanced catalysts.

Selenite-Decorated Polycrystalline NiO Nanosheets Generated from Cathodic Reconstruction for Electrocatalytic Hydrogen Production.

Precatalyst reconstruction in alkaline hydrogen evolution reaction (HER) usually leads to changes in the morphology, composition, and structure, thus improving the catalytic activity, which recently receives intensive attention. However, the design strategies of cathodic reconstruction and the structural features of reconstruction products have not achieved a profound understanding. Here, from the point of thermodynamic stability, metastable nickel selenite dihydrate (NiSeO3·2H2O) is deliberately fabricated as a precatalyst to comprehensively study the reconstruction dynamics in alkaline HER. Multiple in/ex situ techniques capture the geometric, component, and phase evolutions, proving that NiSeO3·2H2O can be transformed into SeO32--decorated polycrystalline NiO nanosheets with rich active sites and good conductivity under alkaline HER conditions, which act as a real catalytic active species. Density functional theory calculations demonstrate that the adsorption of SeO32- can further promote the HER activity of NiO due to the optimized free energy of water activation and hydrogen adsorption. As a result, the SeO32--NiO catalyst exhibits a low overpotential at -10 mA cm-2 (90 mV) and long-term stability (>100 h). This work highlights the targeted design of precatalyst to trigger and utilize cathodic reconstruction and provides an available method for the development of adsorption-modulated efficient electrocatalysts.

Increased Oxygen Vacancies in CeO2 for Improved Electrocatalytic Nitrogen Reduction Performance.

Electrochemical nitrogen fixation is a sustainable and economical strategy to produce ammonia. However, fabricating efficient electrocatalysts for nitrogen fixation is still challenging. Theoretical predictions prove that the oxygen vacancy is able to modulate the electronic state of CeO2 and enhance its electrical conductivity, thus promoting the electrochemical nitrogen reduction reaction (NRR) process. Herein, CeO2 with high oxygen vacancy concentration was prepared via a two-step pyrolysis strategy of Ce metal-organic frameworks (MOFs, denoted H-CeO2). Compared to CeO2 with low oxygen vacancy concentration synthesized via one-step pyrolysis of Ce-MOFs (denoted L-CeO2), H-CeO2 exhibits a large NH3 yield rate (25.64 µg h-1 mgcat-1 at -0.5 V vs reversible hydrogen electrode, RHE) and high faradaic efficiency (FE, 6.3% at -0.4 V vs RHE).

MOF-Derived Cu3P nanoparticles coated with N-doped carbon for nitrogen fixation.

Electrochemical nitrogen reduction is a significant alternative route for synthesizing ammonia, but constructing efficient catalysts for electrochemical nitrogen fixation still faces tough challenges. In this work, Cu3P@NC (NC: nitrogen-doped carbon) nanosheets were prepared via the low-temperature pyrolysis-phosphating of Cu-MOFs. When applied to the nitrogen reduction reaction, Cu3P@NC exhibited a high ammonia yield rate of 10.4 µg h-1 mg-1cat at -0.3 V (vs. RHE) and a faradaic efficiency (FE) of 6.3% at -0.1 V (vs. RHE). The outstanding performance was attributed to the large electrochemical surface area and the defects induced as a result of N doping, which helped enhance N2 adsorption. This work provides a novel strategy for preparing N-doped carbon materials for wide-ranging applications.

Spatial Spillover Effects of Renewable Energy on Carbon Emissions in Less-developed Areas of China.

The purpose of this paper is to determine the spatial spillover effects of renewable energy on carbon emissions in China's less-developed areas. However, few studies have considered this issue from the perspective of less-developed areas. Based on panel data of 21 provinces in China from 2000 to 2017, this paper analyzes the spatial spillover effects of renewable energy on carbon emissions using Moran's I and Spatial Durbin Model (SDM). The results suggest that, first, Moran's I ranges from 0.378 to 0.519, Moran scatter plot presents that provinces are located in the high-high (HH) and low-low (LL) quadrants, indicating provincial carbon emissions in the study area have a significant spatial correlation and agglomeration. Second, under the three matrices, the direct effect coefficients of renewable energy are -0.2522, -0.2639 and -0.2601, this shows that renewable energy is beneficial to local carbon emissions reduction. In contrast, the indirect effect coefficients of renewable energy are 0.0605, 0.1012 and 0.1125, which means higher renewable energy consumption in a single area is conducive to the improvement of carbon emissions to neighbouring areas. Third, urbanization, industrialization, physical capital and other variables have different impacts on local and nearby carbon emissions. This study provides empirical evidence to achieve carbon emission reduction targets by government policymakers.

Impact of Regional Green Development Strategy on Environmental Total Factor Productivity: Evidence from the Yangtze River Economic Belt, China.

Chinese government policy officially identify the Yangtze River Economic Belt (YREB) as one of regional green development strategies firstly in 2014. This strategy can be regarded as quasi-natural experiment, this paper aims to test its impact on regional environmental total factor productivity (TFP). First, slack-based measure model is used to calculate the environmental TFP from 2005 to 2017 at provincial level. Second, based on Chinese official statistics, differences-in-differences (DID) method is applied to construct an evaluation model of policy effect, combining with the kernel matching in propensity score matching (PSM) method. The results show that environmental TFP of YREB has significant spatial differences, with characteristic of high-east and low-west, its average level is 11.69 percentage points higher than the national average. YREB strategy promotes regional economic growth, but it does no effect on the regional environmental TFP yet. Modelling suggests that YREB strategy may play a role in the short term. From the significance of the control variables, infrastructure construction level is positively correlated with environmental TFP, while per capita GDP, financial development and energy consumption intensity have negative effect on environmental TFP. Based on this, policymakers should focus on green development, promoting industrial transformation, and enhancing environmental protection.

Bonding interface boosts the intrinsic activity and durability of NiSe@Fe2O3 heterogeneous electrocatalyst for water oxidation.

The intrinsic activity and durability of oxygen evolution reaction (OER) electrocatalysts are mainly dominated by the surface and interface properties of active materials. Herein, a core-shell heterogeneous structure (NF/NiSe@Fe2O3) is fabricated via two-step hydrothermal method, which exhibits a low overpotential of 220 mV (or 282 mV) at 10 mA/cm2 (or 200 mA/cm2), a small Tafel slope of 36.9 mV/dec, and long-term stability (~230 h) in 1 mol/L KOH for OER. X-ray photoelectron spectroscopy and X-ray absorption spectroscopy reveal the (oxy)hydroxide-rich surface and strong coupling interface between NiSe and Fe2O3 via the Fe-Se bond. Density functional theory calculation suggests that the d-band center and electronic state of NiSe@Fe2O3 heterojunction are well optimized due to the formation of Fe-Se bond, which is favorable for the enhanced OER activity because of the easy adsorption of oxygen-containing intermediates and desorption of O2 in the OER process. In addition, the unique core-shell structure and robust bonding interface are responsible for the good stability for OER. This work provides fundamental insights on the bonding effect that determine the performance of OER electrocatalyst.

Engineering the valence state of ZIF-67 by Cu2O for efficient nonenzymatic glucose detection.

The valence state regulation of Co-based electrocatalysts is extremely important and greatly challenging to enhance the electrochemical performance toward glucose oxidation. Herein, Cu2O@ZIF-67 composites with fine-tuned valence states were rationally constructed for boosting glucose oxidation. X-ray photoelectron spectroscopy (XPS) and cyclic voltammetry (CV) analysis confirm that the content of the high valence state Co (Co3+) in Cu2O@ZIF-67 is much higher than that in the individual ZIF-67 due to the synergistic effects between ZIF-67 and Cu2O. As a result, Co3+-rich Cu2O@ZIF-67 composite exhibits remarkable activity toward glucose electro-oxidation with two linear response ranges of glucose concentration, from 0.01 to 10 mM and 10 to 16.3 mM, high sensitivities of the linear ranges (307.02 and 181.34 µA mM-1 cm-2) as well as a low detection limit (6.5 µM). This research provides a novel avenue for the progress of highly efficient electrocatalysts for nonenzymatic glucose oxidation.

Coupling FeSe2 with CoSe: an effective strategy to create stable and efficient electrocatalysts for water oxidation.

A novel CoSe/FeSe2 nanohybrid electrocatalyst was prepared by a simple one-step hydrothermal method. Owing to the unique interface structure, abundant internal defects, good hydrophilia and electrical coupling effects between different components, the hybrid shows enhanced oxygen evolution reaction (OER) performances, better than those of the individual CoSe and FeSe2.

In situ growth of well-ordered NiFe-MOF-74 on Ni foam by Fe2+ induction as an efficient and stable electrocatalyst for water oxidation.

Well-ordered NiFe-MOF-74 is in situ grown on Ni foam by the induction of Fe2+ and directly used as an OER electrocatalyst. Benefited from the intrinsic open porous structure of MOF-74, the in situ formed MOF arrays and the synergistic effect of Ni and Fe, outstanding water oxidation activity is obtained in alkaline electrolytes with an overpotential of 223 mV at 10 mA cm-2.

Hierarchical ternary Ni-Co-Se nanowires for high-performance supercapacitor device design.

Large-scale uniform Ni-Co-Se bimetallic ternary nanowires have been successfully synthesized through a successive cation exchange. First, NiSe nanowires in situ grown on nickel foam (NF) were prepared by a facile solvothermal route. Next, a series of ternary materials possessing different proportions of Ni and Co were fabricated by a Co-exchange method using the Ni@NiSe material as a template, which effectively achieved morphological inheritance from the parent material. To explore the electrochemical performance, all synthetic materials were assembled into asymmetric supercapacitor devices. Among asymmetric supercapacitor devices, the Ni@Ni0.8Co0.2Se//active carbon (AC) device exhibited a high specific capacitance of 86 F g-1 at a current density of 1 A g-1 and excellent cycling stability with virtually no decrease in capacitance after 2000 continuous charge-discharge cycles. This device still delivered an energy density of 17 Wh kg-1 even at a high power density of 1526.8 W kg-1. These superior electrochemical properties of Ni@Ni0.8Co0.2Se as an electrode material for supercapacitor devices confirmed the synergistic effect between Co and Ni ions, suggesting their potential application in the field of energy storage.