Climbing the Hydrogen Evolution Volcano with a NiTi Shape Memory Alloy.

Alkaline water electrolysis is a sustainable way to produce green hydrogen using renewable electricity. Even though the rates of the cathodic hydrogen evolution reaction (HER) are 2-3 orders of magnitude less under alkaline conditions than under acidic conditions, the possibility of using non-precious metal catalysts makes alkaline HER appealing. We identify a novel and facile route for substantially improving HER performance via the use of commercially available NiTi shape memory alloys, which upon heating undergo a phase transformation from the monoclinic martensite to the cubic austenite structure. While the room-temperature performance is modest, austenitic NiTi outperforms Pt (which is the state-of-the-art HER electrocatalyst) in terms of current density by ≤50% at 80 °C. Surface ensembles presented by the austenite phase are computed with density functional theory to bind hydrogen more weakly than either metallic Ni or Ti and to have binding energies ideally suited for HER.

Boron and nitrogen co-doped carbon nanosheets encapsulating nano iron as an efficient catalyst for electrochemical CO2 reduction utilizing a proton exchange membrane CO2 conversion cell.

Electrochemical carbon dioxide (CO2) reduction, ideally in an aqueous medium, accounts for the sustainable storage of energy from renewable sources in the form of chemical energy in fuels or value-added chemicals. Herein, we report boron and nitrogen co-doped carbon nanosheets encapsulating iron nanocrystals (Fe/BCNNS) as a low cost, highly efficient and precious-metal-free electrocatalyst for the electrochemical reduction of carbon dioxide to formic acid. The porous architecture of the boron and nitrogen co-doped carbon nanosheets along with the active Fe-Nx, N and B sites synergistically allow better three phase contact to enhance the electrocatalytic activity of the cell. Both half-cell as well as full cell measurements have been performed with this particular catalyst. The proton exchange membrane (PEM) CO2 conversion cell is tested under a continuous flow of CO2 gas and is demonstrated to selectively produce a high yield of formic acid due to improved interaction between the catalyst and gas molecules. The maximum yield of formic acid achieved is as high as 94% after 60 min of reaction with Fe/BCNNS as both anode and cathode catalysts. It can be anticipated that such a facile synthesis strategy and excellent electrocatalytic performance of low-cost Fe/BCNNS catalyst can be easily scaled up for industrial applications in electrochemical CO2 conversion.

Nonprecious Catalyst for Three-Phase Contact in a Proton Exchange Membrane CO2 Conversion Full Cell for Efficient Electrochemical Reduction of Carbon Dioxide.

Development of a cost-effective and highly efficient electrocatalyst is essential but challenging in order to convert carbon dioxide to value-added chemicals at ambient conditions. In the current work, the activity of a full electrochemical cell has been demonstrated, utilizing a proton exchange membrane CO2 conversion cell that can selectively convert carbon dioxide to a value-added chemical (formic acid) at room temperature and pressure. A cost-effective, nonprecious-metal-based electrocatalyst, nitrogen-doped carbon nanotubes encapsulating Fe3C nanoparticles (Fe3C@NCNTs), has been reported to exhibit superior catalytic activity toward the electrochemical CO2 reduction reaction (CO2RR). A facile one-step synthesis procedure has been undertaken to synthesize Fe3C@NCNTs. CO2 adsorption takes place via sharing of charge between the nucleophilic anchoring site (Fe3C) and the electrophilic C site of CO2, as shown by the DFT studies. The porous architecture, unique tubular structure, high graphitization degree, and appropriate doping of the Fe3C-encapsulating NCNTs allow better three-phase contact of CO2 (gas), H2O (liquid), and catalyst (solid), which can enhance the electrocatalytic activity of the cell, as demonstrated by the experimental findings. The cell was tested under a continuous flow of CO2 gas and has been demonstrated to produce a good amount of formic acid (HCOOH). The production of formic acid was examined by utilizing UV-vis spectroscopy and high-performance liquid chromatography (HPLC). A series of designed experiments disclosed that the maximum yield of formic acid was as high as 90% with Fe3C@NCNTs as both anode and cathode catalysts. Technology to scale up the reduction procedure has also been proposed and shown in this particular work. These unique observations open a route for the development of cost-effective and highly active platinum-free electrocatalysts for the CO2RR.

Green synthesis of nitrogen-doped self-assembled porous carbon-metal oxide composite towards energy and environmental applications.

Increasing environmental pollution, shortage of efficient energy conversion and storage devices and the depletion of fossil fuels have triggered the research community to look for advanced multifunctional materials suitable for different energy-related applications. Herein, we have discussed a novel and facile synthesis mechanism of such a carbon-based nanocomposite along with its energy and environmental applications. In this present work, nitrogen-doped carbon self-assembled into ordered mesoporous structure has been synthesized via an economical and environment-friendly route and its pore generating mechanism depending on the hydrogen bonding interaction has been highlighted. Incorporation of metal oxide nanoparticles in the porous carbon network has significantly improved CO2 adsorption and lithium storage capacity along with an improvement in the catalytic activity towards Oxygen Reduction Reaction (ORR). Thus our present study unveils a multifunctional material that can be used in three different fields without further modifications.

Magnesium oxide modified nitrogen-doped porous carbon composite as an efficient candidate for high pressure carbon dioxide capture and methane storage.

In this particular work, a simple, cost-effective and single step process to synthesize magnesium oxide modified nitrogen doped porous carbon (MgO/NMC) by thermal decomposition technique has been elaborated and its high-pressure performance as CO2 and CH4 gas adsorbent is demonstrated. The uniformly distributed porous network in the samples was identified from the morphological studies by FESEM and TEM. Elemental analysis and XPS studies were carried out to understand the Mg and N contents. It has been observed that MgO/NMC shows appreciably high CO2 (30 mmol g-1 at 20 bar and 25 °C) as well as CH4 (12 mmol g-1 at 30 bar and 25 °C) adsorption capacity. The surface modification of the samples (caused by the presence of MgO nanoparticles) along with high surface area and good porosity containing interconnected macro-/ meso-/ micropores synergistically improves the adsorption capacity. In addition, high nitrogen content in the nanocomposite enhances the number of basic adsorption sites thereby increasing the gas adsorption capacity. The effect of concentration of MgO on gas adsorption capacities has also been investigated from the adsorption isotherms. The moderate heat of adsorption, as well as good recyclability and selectivity at high pressure, shows that MgO modified nitrogen doped porous carbon composite can be a promising candidate for both CO2 capture and CH4 storage.