Integration of Platinum Group Metal‐Free Catalysts and Bilirubin Oxidase into a Hybrid Material for Oxygen Reduction: Interplay of Chemistry and Morphology

Abstract

Catalytic activity toward the oxygen reduction reaction (ORR) of platinum group metal-free (PGM-free) electrocatalysts integrated with an enzyme (bilirubin oxidase, BOx) in neutral media was studied. The effects of chemical and morphological characteristics of PGM-free materials on the enzyme enhancement of the overall ORR kinetics was investigated. The surface chemistry of the PGM-free catalyst was studied using X-ray Photoelectron Spectroscopy. Catalyst surface morphology was characterized using two independent methods: length-scale specific image analysis and nitrogen adsorption. Good agreement of macroscopic and microscopic morphological properties was found. Enhancement of ORR activity by the enzyme is influenced by chemistry and surface morphology of the catalyst itself. Catalysts with a higher nitrogen content, specifically pyridinic moieties, showed the greatest enhancement. Furthermore, catalysts with a higher fraction of surface roughness in the range of 3-5 nm exhibited greater performance enhancement than catalysts lacking features of this size.

Design of Iron(II) Phthalocyanine‐Derived Oxygen Reduction Electrocatalysts for High‐Power‐Density Microbial Fuel Cells

“…Once again, in this study, the utilization of PGM‐free catalysts resulted in a substantial increase in the power produced compared with that for AC. Among the earth‐abundant metals, Fe was selected for the catalyst because it was previously identified to be more active than other earth‐abundant metals such as Mn, Cu, Co, and Ni 10, 11, 12, 13. This work confirms that PGM‐free catalysts based on iron can boost the performance considerably.…”

“…Therefore, the ORR is severely hampered, which negatively affects the overall MFC performance. The general practice to reduce the overpotentials and accelerate the kinetics is utilization of electrocatalysts on the cathode 10, 11, 12, 13, 14…”

Supercapacitive microbial desalination cells: New class of power generating devices for reduction of salinity content

“…Several oxidants were introduced for the cathodic reaction [73] but oxygen was most effective due to the natural availability (and therefore does not need to be supplied or refilled), low cost, and high electrochemical reduction potential. At the cathode, the oxygen reduction reaction (ORR) pathway can involve 2e − , 2e−x2e − or 4e − [74] , [75] , [76] , [77] , [78] , [79] with final 4e − product H 2 O or OH − depending on the catalyst and the acidic or alkaline environment ( Fig. 2 ) [76] , [77] .…”

Iron-Nicarbazin derived platinum group metal-free electrocatalyst in scalable-size air-breathing cathodes for microbial fuel cells

“…Unfortunately, the activation overpotentials remained still high and measured in roughly 300 mV but lower compared to carbonaceous catalysts [ [43] , [44] , [45] , [46] ]. Several examples have been showed in literature concerning the utilization of earth abundant transition metal such as Fe [ [46] , [47] , [48] , [49] , [50] , [51] , [52] , [53] , [54] , [55] , [56] ], Mn [ [57] , [58] , [59] ], Co [ [60] , [61] , [62] ], Cu [ 63 , 64 ] and Ni [ 65 , 66 ] as catalysts incorporated into cathode adopted in single chamber MFC. So far, Fe-N-C class of materials seems to be the most promising and performing catalysts among the above mentioned [ 17 , 18 , 47 , 50 , 55 , 56 ].…”

“…Moreover, Fe is also the most abundant, cheap and probably the more environmentally friendly among the earth abundant metals and consequently the most suitable for large scale applications in MFC. Among the presented literature, the catalyst is incorporated into air breathing cathode with relatively low dimension (area 3–7 cm 2 ) [ 17 , 18 , 43 , 44 , [47] , [48] , [49] , [50] , [51] , [52] , [53] , [54] , [55] , [56] ]. Scalability of those cathodes for larger reactors are needed and, to the best of our knowledge, not yet presented in literature.…”