Abstract
Since the last decades, non-precious metal catalysts (NPMC), especially iron based electrocatalysts show sufficient activity, potentially applicant in oxygen reduction reaction (ORR), however they only withstand considerable current densities at low operating potentials. On the other hand iron based electrocatalysts are not stable at elevated cathode potentials, which is essential for high energy competence, and its remains difficult to deal. Therefore, via this research a simple approach is demonstrated that allows synthesis of nanosize Fe-doped mayenite electride, [Ca24Al28O64]4+·(e−)4 (can also write as, C12A7−xFex:e−, where doping level, x = 1) (thereafter, Fe-doped C12A7:e−), consist of abundantly available elements with gram level powder material production, based on simple citrate sol-gel method. The maximum achieved conductivity of this first time synthesized Fe-doped C12A7:e− composite materials was 249 S/cm. Consequently, Fe-doped C12A7:e− composite is cost-effective, more active and highly durable precious-metal free electrocatalyst, with 1.03 V onset potential, 0.89 V (RHE) half-wave potential, and ~5.9 mA/cm2 current density, which is higher than benchmark 20% Pt/C (5.65 mA/cm2, and 0.84 V). The Fe-doped C12A7:e− has also higher selectivity for desired 4e− pathway, and more stable than 20 wt% Pt/C electrode with higher immunity towards methanol poisoning. Fe-doped C12A7:e− loses was almost zero of its original activity after passing 11 h compared to the absence of methanol case, indicates that to introduce methanol has almost negligible consequence for ORR performance, which makes it highly desirable, precious-metal free electrocatalyst in ORR. This is primarily described due to coexistence of Fe-doped C12A7:e− related active sites with reduced graphene oxide (rGO) with pyridinic-nitrogen, and their strong coupling consequence along their porous morphology textures. These textures assist rapid diffusion of molecules to catalyst active sites quickly. In real system maximum power densities reached to 243 and 275 mW/cm2 for Pt/C and Fe-doped C12A7:e− composite, respectively.
Highlights
Electronic Science and Technology, Shenzhen University, THz Technical Research Center and Key Laboratory of Optoelectronics Devices and Systems of Ministry of Education and Guangdong Province Shenzhen University, Shenzhen, 518060, China. 4Government Degree college PaharPur, Gomel University, Dera Ismail Khan, K.P.K., Islamic Republic of Pakistan. 5Institute for Advanced Study, Shenzhen University, Shenzhen, Guangdong, 518060, China. 6Key Laboratory of Optoelectronic Devices and Systems of Ministry of Education and Guangdong Provence, College of Optoelectronic Engineering, Shenzhen University, Shenzhen, Guangdong, China, 518060. 7College of Physics and Optoelectronics Engineering, Shenzhen University, Nanhai Ave. 3688, Shenzhen, Guangdong, 518060, China. 8These authors contributed : Karim Khan, Ayesha Khan Tareen and Muhammad Aslam. *email: Clean and renewable energy production is important concern that can replace the conventional energy production devices
From 100–150 °C, weight loss were observed by physically absorb water and dehydration reaction of crystal water in the nitrates evaporates[17], and small endothermic peak confirmed the first citric acid decomposition below the 200 °C, where all citrate conversion after decomposition did not occurs into gaseous products due to the decomposition of nitrate under inert gas environment[18]
It shows that the Fe-doped C12A7:e− composite is very active in the oxygen reduction reaction (ORR) and exhibits higher electrocatalytic activity, which could be demonstrated from its superior current density and more positive half-wave potential
Summary
For Fe-doped C12A7:e− composite, 0.89 V (vs RHE) half wave potential and ~5.9 mA.cm−2 current density were superior than the 20% Pt/C (5.65 mA.cm−2, and 0.84 V), which shows the elevated electrocatalytic activity of the Fe-doped C12A7:e− for ORR in fuel cell Another important factor regarding to the application as electrocatalyst electrode material is number of electrons transfer during the ORR process[15]. Our investigation for “Fe” doping on the electrical properties of the C12A7:e− show that above results manifest the feasibility of this sol-gel method for the cation doping, for further boosting the electrocatalytic applications It shows that the Fe-doped C12A7:e− composite is very active in the ORR and exhibits higher electrocatalytic activity, which could be demonstrated from its superior current density and more positive half-wave potential. This concept paves the way for a new class of hybrid electrocatalysts, where activity and stability of the electrocatalysts are addressed
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