<h3>Title</h3>
<h3><span style="font-size: 12.16px;">Investigations on Functional Materials for Hybrid Sulfur Cycle for Thermochemical Hydrogen Production</span></h3>
<p><strong><span style="font-size: 12.16px;"><span style="text-decoration: underline;">Abstract</span> :</span></strong></p>
<p class="MsoNormal" style="text-align: justify; mso-layout-grid-align: none; text-autospace: none;"><span style="font-size: 11.0pt; color: black; mso-ansi-language: EN-IN; mso-fareast-language: EN-IN;">Thermochemical water splitting cycles has shown great potential towards efficient production of hydrogen on an industrial scale. Hybrid Sulfur cycle (Hy-S) is one of the most preferably studied thermochemical cycle due to several advantages. Hy-S cycle involves two steps, i.e. sulfuric acid decomposition reaction and aqueous SO<sub>2</sub></span><span style="font-size: 11.0pt; color: black; mso-ansi-language: EN-IN; mso-fareast-language: EN-IN;">electrolysis. Development of functional materials such as catalysts, electrocatalysts, membrane electrode assemblies etc., was undertaken with an objective to improve the reaction kinetics and efficiency of the Hy-S cycle. </span></p>
<p class="MsoNormal" style="text-align: justify; mso-layout-grid-align: none; text-autospace: none;"><span style="font-size: 11.0pt; color: black; mso-ansi-language: EN-IN; mso-fareast-language: EN-IN;">     Iron oxide based catalyst was chosen and efforts were made to overcome the sintering issues encountered during its prolonged uses. For the purpose, dispersed iron oxide (15 wt.%) on various supports (SiO<sub>2</sub>, TiO<sub>2</sub>, CeO<sub>2</sub></span><span style="font-size: 11.0pt; color: black; mso-ansi-language: EN-IN; mso-fareast-language: EN-IN;">and ZrO<sub>2</sub>) were synthesized and evaluated their activity for sulfuric acid decomposition reaction. The catalytic activity for the acid decomposition at 750°C followed the order: Fe<sub>2</sub>O<sub>3</sub>/SiO<sub>2</sub>&gt; Fe<sub>2</sub>TiO<sub>5</sub>/TiO<sub>2</sub>&gt; Fe<sub>2</sub>O<sub>3</sub>/ZrO<sub>2</sub>&gt; Fe<sub>2</sub>O<sub>3</sub>/CeO<sub>2</sub>. Various preparation methods like polyol, wet-impregnation, hydrothermal and equilibrium adsorption were also employed to maximize the catalyst performance of Fe<sub>2</sub>O<sub>3</sub>/SiO<sub>2</sub></span><span style="font-size: 11.0pt; color: black; mso-ansi-language: EN-IN; mso-fareast-language: EN-IN;">catalyst for acid decomposition reaction. The Fe<sub>2</sub>O<sub>3 </sub>(15wt.%)/SiO<sub>2</sub></span><span style="font-size: 11.0pt; color: black; mso-ansi-language: EN-IN; mso-fareast-language: EN-IN;">samples prepared by polyol method exhibited highest activity for the sulfuric acid decomposition reaction and the activity trend at 800 °C was found to be as follows: polyol &gt; equilibrium-adsorption&gt; wet-impregnation ~ hydrothermal. Further stability of Fe<sub>2</sub>O<sub>3</sub></span><span style="font-size: 11.0pt; color: black; mso-ansi-language: EN-IN; mso-fareast-language: EN-IN;">(15wt.%)/SiO</span><span style="font-size: 7.0pt; color: black; mso-ansi-language: EN-IN; mso-fareast-language: EN-IN;">2 </span><span style="font-size: 11.0pt; color: black; mso-ansi-language: EN-IN; mso-fareast-language: EN-IN;">catalyst during prolonged uses (100 h) for sulfuric acid decomposition reaction at 800 °C was evaluated. </span></p>
<p class="MsoNormal" style="text-align: justify; mso-layout-grid-align: none; text-autospace: none;"><span style="font-size: 11.0pt; color: black; mso-ansi-language: EN-IN; mso-fareast-language: EN-IN;">     The catalytic properties of the dispersed iron oxide samples were correlated to nature of support, structure, morphology and the redox properties of iron oxide phase. Detailed investigations on both fresh and used catalyst were studied to elucidate the mechanistic aspects of the acid decomposition process. The most probable mechanism of sulfuric acid decomposition over dispersed iron oxide catalyst which involved formation and decomposition of surface sulfate species was proposed. </span></p>
<p class="MsoNormal" style="text-align: justify; mso-layout-grid-align: none; text-autospace: none;"><span style="font-size: 11.0pt; color: black; mso-ansi-language: EN-IN; mso-fareast-language: EN-IN;">     Solar thermal sulfuric acid decomposition employing concentrated solar heat from a 1.8 m diameter dish and in-house developed quartz receiver-reactor was also successfully demonstrated. A maximum SO<sub>2</sub></span><span style="font-size: 11.0pt; color: black; mso-ansi-language: EN-IN; mso-fareast-language: EN-IN;">yield of 38 % was achieved with Fe<sub>2</sub>O<sub>3</sub>/(15wt. %)/SiO<sub>2</sub></span><span style="font-size: 11.0pt; color: black; mso-ansi-language: EN-IN; mso-fareast-language: EN-IN;">catalyst at weight hourly space velocity (WHSV) of ~ 28 g acid/gcat/h, at 750-850 <em>°</em>C<em>. </em></span></p>
<p style="text-align: justify;"><span style="font-size: 10.0pt; font-family: 'Times New Roman','serif'; mso-fareast-font-family: 'Times New Roman'; color: black; mso-ansi-language: EN-IN; mso-fareast-language: EN-IN; mso-bidi-language: AR-SA;">     A series of <em>Pt/C </em>electrocatalysts with varying platinum content (10-40 wt.%) were successfully prepared and electrochemical properties were tested for hydrogen evolution reaction(HER) and aqueous SO</span><sub><span style="font-size: 11.0pt; font-family: 'Times New Roman','serif'; mso-fareast-font-family: 'Times New Roman'; color: black; mso-ansi-language: EN-IN; mso-fareast-language: EN-IN; mso-bidi-language: AR-SA;">2</span></sub><span style="font-size: 10.0pt; font-family: 'Times New Roman','serif'; mso-fareast-font-family: 'Times New Roman'; color: black; mso-ansi-language: EN-IN; mso-fareast-language: EN-IN; mso-bidi-language: AR-SA;">oxidation reaction. Amongst these, catalyst containing 20 wt. % Pt was found to be the most effective. Further, a single cell PEM based aqueous SO</span><sub><span style="font-size: 11.0pt; font-family: 'Times New Roman','serif'; mso-fareast-font-family: 'Times New Roman'; color: black; mso-ansi-language: EN-IN; mso-fareast-language: EN-IN; mso-bidi-language: AR-SA;">2</span></sub><span style="font-size: 10.0pt; font-family: 'Times New Roman','serif'; mso-fareast-font-family: 'Times New Roman'; color: black; mso-ansi-language: EN-IN; mso-fareast-language: EN-IN; mso-bidi-language: AR-SA;">electrolyzer (4cm</span><span style="font-size: 7.0pt; font-family: 'Times New Roman','serif'; mso-fareast-font-family: 'Times New Roman'; color: black; mso-ansi-language: EN-IN; mso-fareast-language: EN-IN; mso-bidi-language: AR-SA;">2 </span><span style="font-size: 10.0pt; font-family: 'Times New Roman','serif'; mso-fareast-font-family: 'Times New Roman'; color: black; mso-ansi-language: EN-IN; mso-fareast-language: EN-IN; mso-bidi-language: AR-SA;">active area) was designed, fabricated and tested with the membrane electrode assembly comprising of the most active <em>Pt/C </em>electrocatalyst. A current density of ~75 mAcm</span><sup><span style="font-size: 11.0pt; font-family: 'Times New Roman','serif'; mso-fareast-font-family: 'Times New Roman'; color: black; mso-ansi-language: EN-IN; mso-fareast-language: EN-IN; mso-bidi-language: AR-SA;">2 </span></sup><span style="font-size: 10.0pt; font-family: 'Times New Roman','serif'; mso-fareast-font-family: 'Times New Roman'; color: black; mso-ansi-language: EN-IN; mso-fareast-language: EN-IN; mso-bidi-language: AR-SA;">was achieved at a cell voltage of 1 V. As a non-noble metal based electrocatalyst, molybdenum carbide electrocatalysts dispersed on carbon with varying Mo content (10-40 wt.%) were synthesized and evaluated for HER. Through these studies 20 wt% Mo content was found to be the optimum loading to attain maximum electroactivity for HER.</span></p>