Periodic Reporting for period 1 - HydrogenLung (Lung-like gas supply for hydrogen oxidation reaction in fuel cell anode)
Berichtszeitraum: 2021-02-01 bis 2023-01-31
Hydrogen is a clean and sustainable energy carrier, which is important for the sustainable development of the society. Hydrogen fuel cells are the most important technology for converting the chemical energy in hydrogen into electricity. Yet, polymer electrolyte membrane fuel cells (PEMFC) utilize scarce and geopolitically problematic platinum (Pt) as a catalyst to promote the hydrogen oxidation reaction (HOR). Most studies on HOR, from the aspect of catalysts, concern the activity and stability, while only a few investigations study gas transport, which also affects the HOR rate and thus the overall efficiency of a fuel cell. Here, enlightened by lungs’ supply of oxygen to human with multistage bronchi and pulmonary alveoli, we have aimed to improve hydrogen gas diffusion at the catalyst layer (CL) by constructing multistage superaerophilic gas channels (MSGC) that are all open to the gas source and penetrate deep into CL, where catalysts and electrolytes are located and HOR takes place. The overall aim is to improve the overall efficiency while reducing the amount the precious Pt in the catalyst and thus achieving more sustainable conversion of chemical energy into electricity in PEMFCs.
The scientific goal of the HydrogenLung action is to construct lung-like MSGC for a hydrogen electrode of a fuel cell to accelerate hydrogen diffusion and thus promote the HOR. As shown in Figure 1a, one of the HydrogeLung action targets was to develop a procedure for synthesizing a catalyst with low Pt loading but high activity for promoting HOR using specific tungsten based nanoarray support. As shown in Figure 1b,the second target was to develop the wettability controlled gas channel structure for promoting gas transfer by utilizing the optimized Pt-on-tungsten electrocatalyst. As shown in Figure 1c, the ultimate goal was to integrate the developed and optimized electrode structure in a PEMFC setup to showcase its relevance by achieving similar or higher power density than with a commercial reference electrode but with lower precious Pt metal loading.
Hydrogen technologies are one of the key technologies in the ongoing Green Transition. Fuel cells convert the chemical bond energy of hydrogen into electricity with a relatively good efficiency and, importantly, without other emissions but water. Among the various fuel cell technologies, the PEMFC is the most attractive alternative for applications requiring high power and energy density alongside with operational flexibility, e.g. heavy duty vehicles. However, PEMFC, similar to many other Green Transition technologies, relay on utilizing metals extracted from non-renewable minerals. To enable sustainable Green Transition, we must develop these technologies so that they utilize efficiently these non-renewable precious metals so that their amount can be reduced - while still sustaining or improving energy efficient operation. Hence, the HydrogenLung action furthers Green Transition by introducing one approach to improve sustainability of PEMFCs. This approach can also be applied to other electrochemical devices with gaseous reactants, such as waste CO2 electrochemical valorization to chemicals.
The scientific goal of the HydrogenLung action is to construct lung-like MSGC for a hydrogen electrode of a fuel cell to accelerate hydrogen diffusion and thus promote the HOR. As shown in Figure 1a, one of the HydrogeLung action targets was to develop a procedure for synthesizing a catalyst with low Pt loading but high activity for promoting HOR using specific tungsten based nanoarray support. As shown in Figure 1b,the second target was to develop the wettability controlled gas channel structure for promoting gas transfer by utilizing the optimized Pt-on-tungsten electrocatalyst. As shown in Figure 1c, the ultimate goal was to integrate the developed and optimized electrode structure in a PEMFC setup to showcase its relevance by achieving similar or higher power density than with a commercial reference electrode but with lower precious Pt metal loading.
Hydrogen technologies are one of the key technologies in the ongoing Green Transition. Fuel cells convert the chemical bond energy of hydrogen into electricity with a relatively good efficiency and, importantly, without other emissions but water. Among the various fuel cell technologies, the PEMFC is the most attractive alternative for applications requiring high power and energy density alongside with operational flexibility, e.g. heavy duty vehicles. However, PEMFC, similar to many other Green Transition technologies, relay on utilizing metals extracted from non-renewable minerals. To enable sustainable Green Transition, we must develop these technologies so that they utilize efficiently these non-renewable precious metals so that their amount can be reduced - while still sustaining or improving energy efficient operation. Hence, the HydrogenLung action furthers Green Transition by introducing one approach to improve sustainability of PEMFCs. This approach can also be applied to other electrochemical devices with gaseous reactants, such as waste CO2 electrochemical valorization to chemicals.
During the HydrogenLung action, we have first optimized a process for fabricating an HOR catalyst where Pt is finely dispersed on a tungsten oxide (WO3) support. The WO3 support synthetized had a specific 3D nanoarray structure, which enabled construction of the wettability controlled gas diffusion channels. In addition to this catalyst structure, we also developed and optimized the coating on the 3D support so that hydrophobic gas diffusion and hydrophilic water diffusion pathways alter in the structure. This enabled optimal transfer of both the reacting hydrogen and water needed for humidifying the polymer membrane so that its activity was preserved during the operation at elevated temperature. As a final step, we integrated the developed electrode structure in a laboratory scale fuel cell.
We have also investigated utilizing similar approach for promoting CO2 conversion to formate. As a catalyst, we utilized bismuth oxide known for its ability to promote selective formate generation and developed similar type of wettability controlling electrode structure as for the hydrogen electrode. The relevance of this CO2-to-formate conversion electrode for achieving more stable and efficient formate generation was demonstrated in a laboratory scale flow cell.
Our findings on CO2 conversion are presented in a scientific publication. Moreover, one manuscript is submitted for peer evaluation in an international journal while writing two manuscripts is in progress. The project results have been presented in three conferences for scientific and industrial audience and also during fairs targeted for chemistry professionals. To attract young talents into the field, the HydrogeLung results have been also introduced to high school students in two separate sessions.
We have also investigated utilizing similar approach for promoting CO2 conversion to formate. As a catalyst, we utilized bismuth oxide known for its ability to promote selective formate generation and developed similar type of wettability controlling electrode structure as for the hydrogen electrode. The relevance of this CO2-to-formate conversion electrode for achieving more stable and efficient formate generation was demonstrated in a laboratory scale flow cell.
Our findings on CO2 conversion are presented in a scientific publication. Moreover, one manuscript is submitted for peer evaluation in an international journal while writing two manuscripts is in progress. The project results have been presented in three conferences for scientific and industrial audience and also during fairs targeted for chemistry professionals. To attract young talents into the field, the HydrogeLung results have been also introduced to high school students in two separate sessions.
The wettability controlling gas channel design is proved effective during the HydrogenLung action: the power output of the fuel cell improves about 160 % with the special MSGC developed when compared with a PEMFC setup without MSGC but utilizing the same 3D catalyst (Pt supported on a WO3 nanoarray). Performance improvement is also observed when a similar strategy is applied for promoting CO2 reduction on a Bi2O3 electrocatalyst to boost the CO2-to-formate conversion. The stability of the setup is extended from 1 h to 12 h and the potential range where >90% formate selectivity is achieved is notably broadened. These achievements enable more flexible formate generation and have thus relevance when considering industrial CO2-to-formate conversion.
While exploring the hydrogen fuel cell, we have also developed a method for applying 3D catalysts on a proton exchange membrane based water electrolyser for generating hydrogen, based on a tungsten carbide nanoarray (WC NA) electrocatalyst for hydrogen evolution reaction. The hydrogen generation at cell voltage of 1.9 V is improved about 60% compared with a setup utilizing the same electrocatalyst but without the 3D structure. Basing on the above findings, we have also developed an efficient electrocatalyst (amorphous carbon modulated-quantum dots NiO) for promoting oxygen evolution reaction during water electrolysis in an anion exchange membrane electrolyser (AEMEL). An ambitious current density of 500 mA cm-2 is achieved at 1 .7 V with a lab-scale AEMEL.
The HydrogenLung action result can be utilized to develop more sustainable electrochemical cells utilizing less precious nonrenewable metals but still operating efficiently. These technologies are inevitable for furthering Green Transition and to decarbonising the industrial and transport sectors. The existing and emerging electrochemical conversion technologies are not important only from the environmental aspects but they also contribute to improving EU's security of supply of raw materials and energy by enabling energy storing in the form of chemical energy and thus supporting the intermittent renewable energy generation and by offering an alternative method for producing chemicals instead of using fossil based raw materials.
While exploring the hydrogen fuel cell, we have also developed a method for applying 3D catalysts on a proton exchange membrane based water electrolyser for generating hydrogen, based on a tungsten carbide nanoarray (WC NA) electrocatalyst for hydrogen evolution reaction. The hydrogen generation at cell voltage of 1.9 V is improved about 60% compared with a setup utilizing the same electrocatalyst but without the 3D structure. Basing on the above findings, we have also developed an efficient electrocatalyst (amorphous carbon modulated-quantum dots NiO) for promoting oxygen evolution reaction during water electrolysis in an anion exchange membrane electrolyser (AEMEL). An ambitious current density of 500 mA cm-2 is achieved at 1 .7 V with a lab-scale AEMEL.
The HydrogenLung action result can be utilized to develop more sustainable electrochemical cells utilizing less precious nonrenewable metals but still operating efficiently. These technologies are inevitable for furthering Green Transition and to decarbonising the industrial and transport sectors. The existing and emerging electrochemical conversion technologies are not important only from the environmental aspects but they also contribute to improving EU's security of supply of raw materials and energy by enabling energy storing in the form of chemical energy and thus supporting the intermittent renewable energy generation and by offering an alternative method for producing chemicals instead of using fossil based raw materials.