Exploring In Situ Kinetics of Oxygen Vacancy-Rich B/PIncorporated Cobalt-Oxide Nanowires for Oxygen Evolution Reaction

Defect-engineering of transition-metal oxide-based nanocatalysts is an innovative approach for improving the oxygen evolution reaction (OER) owing to their enhanced activity and stability. The present study introduces a facile approach aimed at enhancing OER activity by incorporating boron and phosphorus into cobalt oxide nanowires (B/P-CoOx NWs). The resulting material, enriched with oxygen vacancies (Ov), as confirmed by X-ray photoelectron spectroscopy (XPS) and electron paramagnetic resonance (EPR), induced a complete structural transformation from Co3O4 to a CoO phase. The B/P-CoOx NWs exhibited an impressive overpotential of only 230 mV to achieve a current density of 10 mA cm-2 in 1 M KOH. The presence of Ov was proved to be responsible for the improvement in conductivity along with the quantity and quality of active sites. Electrochemical kinetic analysis was performed to reveal the crucial role of Ov in facilitating the OER mechanism by enhancing the adsorption and desorption of OH- ions and O2 molecules from the surface. The robustness of the developed electrocatalyst was demonstrated through a chronoamperometric test conducted over 80 h and a recyclability test spanning 10 000 cycles. This study focuses on the fabrication and dynamic investigation of the electrocatalyst, laying the groundwork for further advancements in non-noble material-based electrocatalysts

Unveiling the synergistic effect of amorphous CoW-phospho-borides for overall alkaline water electrolysis

Amorphous transition-metal-phospho-borides (TMPBs) are emerging as a new class of hybrid bifunctional catalysts for water-splitting. The present work reports the discovery of CoWPB as a new promising material that adds to the smaller family of TMPBs. The optimized compositions, namely Co4WPB5 and Co2WPB1 could achieve 10 mA/cm2 at just 72 mV and 262 mV of overpotentials for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER), respectively, in 1 M KOH. Furthermore, the catalyst showed good performance in a 2-electrode assembly (1.59 V for 10 mA/cm2) with considerable stability (70 h stability, 10,000 operating cycles). Detailed morphological and electrochemical characterizations unveiled insights into the role of all elements in catalyst's improved performance. The presence of W was found to be crucial in improving the electronic conductivity and charge redistribution, making CoWPB suitable for both HER and OER. In computational simulation analysis, two configurations with different atomic environments, namely, CoWPBH and CoWPBO were found to have the lowest calculated overpotentials for HER and OER, respectively. It was found that the surface P-sites in CoWPBH were HER-active while the Co-sites in CoWPBO were OER-active sites. The study presents new knowledge about active sites in such multi-component catalysts that will foster more advancement in the area of water electrolysis

Unveiling the Kinetics of Oxygen Evolution Reaction in Defect-Engineered B/P incorporated Cobalt-Oxide Electrocatalysts

Defect-rich transition-metal oxide electrocatalysts hold great promise for alkaline water electrolysis due to their enhanced activity and stability. This study presents a new strategy that significantly improve the OER activity of Co-oxide nanosheets through incorporation of B and P (B/P-CoOx NS), eventually leading to abundant surface defects and oxygen vacancies. The B/P-CoOx NS demonstrates low overpotential of 220 mV to achieve 10 mA/cm2. The electrochemical and kinetic studies coupled with conventional morphological and structural characterizations, reveal that various crystalline defects like vacancies, dislocations, twin planes, and grain boundaries play crucial roles in promoting the OH− ion adsorption, the formation of intermediates, and the desorption of oxygen molecules. The industrial viability of the developed electrocatalyst is substantiated through assessments under harsh industrial conditions of 6 M KOH at 60 °C in a zero-gap single-cell alkaline electrolyzer which achieves 1 A/cm2 at 1.95 V. Chronoamperometry tests (100 h) highlight remarkable robustness of the electrocatalyst. This work establishes a new strategy to fabricate defect-rich OER electrocatalysts, setting a precedent to achieve better OER rates with non-noble materials

Development of efficient designs of cooking systems. I. Experimental

In the conventional cooking practice, where a pot or a pan is directly placed on a flame, the thermal energy efficiency is in the range of 10-25%. It was thought desirable to increase this efficiency up to 60% or more. The cooking systems can be of various sizes. In the developing world (85% of the worlds population), open pan cooking is largely still practiced at the family level (4-10 people) or at the community level (50-2000 people or more). The latter requirement is encountered in schools, homes for senior citizens, jails, social and/or religious centers (temples, mosques, churches), social and/or educational functions (conferences, marriages, celebrations, etc.), remand homes, etc. For these different types of final application, in the present work, cooking systems have been developed. A systematic work has has been reported regarding the effect of several parameters on thermal efficiency. The parameters include the cooker size, number of pots, size and aspect ratio of the pots, heat flux, flame size, flux-time relationship, insulating alternatives, etc. Local and global optima of the parameters have been obtained, resulting in thermal efficiency of about 70%. © 2011 American Chemical Society

Development of efficient designs of cooking systems. II. Computational fluid dynamics and optimization

Sections 2-6 of Part I were devoted to the analysis of heat transfer characteristics of cookers. In all the experiments, only water was employed as a working medium. Now, we extend such an analysis to the actual cooking process in order to arrive at an improved cooking device. The major strategies for the optimization of energy utilization is to design appropriate insulation that has been obtained by two cover vessels. In order to select an air gap, the flow and temperature patterns in the air gap have been extensively analyzed using computational fluid dynamics (CFD). The flow pattern and heat transfer in cooking pots have also been analyzed by CFD. This has enabled us to design suitable internals for minimizing the stratification of temperature. The understanding of fluid mechanics has also given basis for selection of heat flux, gap between burner tip and cooker bottom, and temperature of flue gases leaving the cooker. Chemical engineering principles have been used for modeling and optimization. Kinetics have been obtained in batch cookers. The knowledge of kinetics, thermal mixing, axial mixing, and optimum selection of insulation have been employed for the development of continuous cookers. The continuous mode of operation also helps in saving of energy. Systematic data have been collected for the design and scale up of continuous cookers. © 2011 American Chemical Society