There have been many advancements in the search for an oxygen reduction reaction (ORR) catalyst that exhibits strong performance and exceptional durability using low-cost materials. Although recent advancements have focused on matching or surpassing the ORR performance of Pt/C, exploring ways to improve the durability of electrocatalysts on longer time scales has not been adequately addressed. In this work, a high-performance and stable ORR electrocatalyst was produced using a simple nitrogen-doping protocol on GUITAR (pseudo-Graphite from the University of Idaho Thermolyzed Asphalt Reaction)-coated Ketjen black (N′-GUITAR/KB). X-ray photoelectron spectroscopy indicates selective doping of pyridinic and pyrrolic moieties (total N abundance of 0.9%). Voltammetric experiments in O2-saturated 0.1 M KOH indicate that the electrocatalyst is exceptionally stable and one of the highest performers regarding overvoltage and current density. The system maintained its electrocatalytic performance throughout the Department of Energy stress protocol, which consists of 30,000 convective cyclic voltammetry cycles in O2-saturated 0.1 M KOH. This remarkable stability, along with the low-cost synthesis, represents an important milestone in overcoming the challenges that prevent wide-scale adoption of fuel cell technology.

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The carbon material, GUITAR (pseudo-graphite from the University of Idaho thermolyzed asphalt reaction) can be doped with nitrogen in two prevalent forms. In a previous study N(py)-GUITAR had a predominance of pyridinic and pyrrolic moieties with no graphitic nitrogen. In this study N(g)-GUITAR contains a 9.7 % N atomic abundance, with that fraction consisting of 72.3 % graphitic, 23.7 % pyridinic, and 0 % pyrrolic nitrogen. The two materials allow for the examination of hypotheses regarding the importance of the three different nitrogen moieties in the oxygen reduction reaction (ORR). In the previous investigation, the lack of graphitic nitrogen of N(py)-GUITAR gave a preferred pathway of 4e- ORR to H2O. In this investigation, N(g)-GUITAR gave a 2e- ORR pathway to H2O2. This was elucidated by current efficiency and hydrodynamic voltammetry studies. The high predominance of graphitic nitrogen confirms the hypothesis regarding 2e- vs. 4e- ORR pathways with N-doped carbon materials. N(g)-GUITAR was also evaluated for parasitic pathways for H2O2 production. At -0.95 V vs. Ag/AgCl the combination of current efficiency for H2O2 is 96 % in 0.05 M Na2SO4 with a production rate of 4.9 mg cm-2 h-1, is the highest reported in the literature. This indicates possibilities for water purification and treatment applications, which require 10 to 250 mg L-1, depending on conditions.

We investigated electrochemical sensors based on graphite oxide (GrO) and oxidized carbon black (CbO). GrO and CbO were synthesized by the modified Hummers method. Single-stranded DNA (ssDNA) probes were synthesized with a 5′ primary amine for attachment. These ssDNA oligonucleotides were immobilized on GrO and CbO using standard 1-ethyl-3-(3-dimethyl aminopropyl) carbodiimide (EDC) coupling. This formed an amide bond between the DNA-amine and carboxyl groups on GrO and CbO. GrO and CbO were used instead of graphite in a carbon paste material. This significantly enhanced the sensitivity of the biosensor for the reverse-complementary DNA. We detected reverse-complimentary DNA using Electrochemical Impedance Spectroscopy (EIS) and Cyclic Voltammetry (CV) in a ferricyanide solution. The solution was spiked with the ssDNA oligonucleotide with the reverse-complementary sequence of the immobilized probe. The change in current or impedance was measured. We present early work on optimizing the fabrication method for DNA-functionalized carbon electrodes. Working electrodes were fabricated by drop-casting the active material onto a glassy carbon electrode surface.