Regulating the Electronic Structure of Cu–N_x Active Sites for Efficient and Durable Oxygen Reduction Catalysis to Improve Microbial Fuel Cell Performance

Abstract

The efficient and durable oxygen reduction reaction (ORR) catalyst is of great significance to boost power generation and pollutant degradation in microbial fuel cells (MFCs). Although transition metal–nitrogen-codoped carbon materials are an important class of ORR catalysts, copper–nitrogen-codoped carbon is not considered a suitable MFC cathode catalyst due to the insufficient performance and especially instability. Herein, we report a three-dimensional (3D) hierarchical porous copper, nitrogen, and boron codoped carbon (3DHP Cu–N/B–C) catalyst synthesized by the dual template method. The introduced B atom as an electron donor increases the electron density around the Cu–N x active site, which significantly promotes the efficiency of the ORR process and stabilizes the active site by preventing demetallization. Thus, the 3DHP Cu–N/B–C catalyst exhibited excellent ORR performance with the half-wave potential of 0.83 V (vs reversible hydrogen electrode (RHE)) in a 0.1 M KOH electrolyte and 0.68 V (vs RHE) in a 50 mM PBS electrolyte. Meanwhile, 3DHP Cu–N/B–C had satisfactory stability with 94.16% current retention after 24 h of chronoamperometry test, which is better than that of 20% Pt/C. The MFCs using 3DHP Cu–N/B–C not only showed a maximum power density of up to 760.14 ± 19.03 mW m–2 but also operating durability of more than 50 days. Moreover, the 16S rDNA sequencing results presented that the 3DHP Cu–N/B–C catalyst had a positive effect on the microbial community of the MFC with more anaerobic electroactive bacteria in the anode biofilm and fewer aerobic bacteria in the cathode biofilm. This study provides a new approach for the development of Cu-based ORR electrocatalysts as well as guidance for the rational design of high-performance MFCs.

Highly Accessible Co–Nx Active Sites-Doped Carbon Framework with Uniformly Dispersed Cobalt Nanoparticles for the Oxygen Reduction Reaction in Alkaline and Neutral Electrolytes

“…24−26 The highresolution N 1s spectra (Figure 3c) can be deconvoluted into four peaks located at 398.3, 399, 400, and 401.1 eV, corresponding to pyridinic N, Co−N x , pyrrolic N, and graphitic N, respectively. 27,28 This proves the coordination of Co and N in the carbon framework. The Co−N x active sites help tune the charge distribution and electronic properties of the electrocatalysts, promote the adsorption of reaction intermediates, and further enhance the corresponding reaction activities.…”

“…The high-resolution C 1s spectra are shown in Figure b, which can be deconvoluted into three peaks at 284.7, 286.5, and 288.9 eV, corresponding to C–C, C–N, and CO bonds, respectively. − The high-resolution N 1s spectra (Figure c) can be deconvoluted into four peaks located at 398.3, 399, 400, and 401.1 eV, corresponding to pyridinic N, Co–N x , pyrrolic N, and graphitic N, respectively. , This proves the coordination of Co and N in the carbon framework. The Co–N x active sites help tune the charge distribution and electronic properties of the electrocatalysts, promote the adsorption of reaction intermediates, and further enhance the corresponding reaction activities. − The nitrogen content for Co-N/C-800@MCA-ZIF-67-C is 13.23%, as listed in Table S1. Both pyridine N and graphite N coordinate with Co to form Co–N x molecules, and the nitrogen atoms are stabilized in the carbon matrix through the formation of Co–N bonds, which are progressively lost once the cobalt nanoparticles are aggregated because the remaining N–C bonds cannot effectively bind the carbon atoms without the presence of Co–N bonds. , Considering that the valence state of the Co element is significant for the electrochemical performance of the sample, the peak deconvolution of Co 2p for all samples is displayed in Figure d.…”

Facilely prepared carbon dots as effective anode modifier for enhanced performance of microbial fuel cells

“…3d, the protein concentration of the bio lm on the modi ed anode (121.43 ± 19.7 µg mL − 1 ) was signi cantly higher than that of the blank group (105.80 ± 12.0 µg mL − 1 ). In addition to providing more charge-producing bacteria, the thicker bio lm was better able to resist external interference and facilitated the stable output of the MFCs [34]. This further con rmed that carbon dots modi cation promoted the loading of microorganisms on the anode, which enhanced the performance of the anode and contributed to the improvement of MFC power production.…”

Atomically Dispersed Cu Nanostructures with pH-Universal Electrocatalytic Oxygen Reduction Activity for Zn–Air Batteries

“…The exhaustion of traditional energy forces us to explore new energy conversion and storage techniques such as metal–air batteries and fuel cells with low carbon emission, meeting the increasing energy demand of social development. − Among them, the Zn–air battery is considered as one of the most prospective technologies for energy storage owing to the high energy density, considerable safety, and environmental friendliness. , However, the sluggish cathodic oxygen reduction reaction (ORR) involving a multielectron transfer process is one of the main obstacles to the development of Zn–air batteries. − Although noble-metal-based electrocatalysts, especially platinum (Pt-based catalysts), are state-of-the-art ORR catalysts, their large-scale commercialization is significantly blocked by the drawback of high cost and poor durability. − So far, more durable and cost-effective non-noble-metal catalysts are identified as substitutes to Pt-based catalysts for ORR.…”