Nitrogen-doped graphene catalysts: High energy wet ball milling synthesis and characterizations of functional groups and particle size variation with time and speed

Abstract

Summary Nitrogen‐doped graphene (N‐G) catalyst emerges as one of the promising non‐platinum group metal (non‐PGM) catalysts with the advantages of low cost, high oxygen reduction reaction (ORR) activity, stability, and selectivity to replace expensive PGM catalysts in electrochemical systems. In this research, nanoscale high energy wet (NHEW) ball milling is first investigated for the synthesis of N‐G catalysts to make conventional problems such as sintering or localized overheating issues negligible. The successful synthesis of N‐G catalysts with comparable catalytic performance to 10 wt% Pt/C by using this method has been published. This paper focuses on understanding the effect of grinding speed and grinding time on the particle size and chemical state of N‐G catalysts through the physical and chemical characterization. The research result shows that (1) the final particle size, nitrogen doping percentage, and nitrogen bonding composition of synthesized N‐G catalysts are predictable and controllable by adjusting the grinding time, the grinding speed, and other relative experimental parameters; (2) the final particle size of N‐G catalysts could be estimated from the derived relation between the cracking energy density and the particle size of ground material in the NHEW ball milling process with specified experimental parameters; and (3) the chemical composition of N‐G catalysts synthesized by NHEW ball milling is controllable by adjusting the grinding time and grinding speed.

Noble‐free oxygen reduction reaction catalyst supported on Sengon wood ( Paraserianthes falcataria L. ) derived reduced graphene oxide for fuel cell application

“…This is attributed to the effect of heat treatment at higher temperature through pyrolysis that has removed greater amount of oxygen-containing groups and caused a breakage on sp 2 bond in graphene layers into sp 3 bond, leading to higher vacancy defects on the surface. 28,29 The success of the synthesis of RGO was further confirmed by the XRD spectra in Figure 1B. The diffraction peaks at 2θ values of 25 to 26 and 44 , which correspond to the (002) and (100) planes, respectively, confirmed the formation of RGO, and the lack of peak at 10 indicated that the GO was reduced to RGO for all samples.…”

“…The increase in pyrolysis temperature to produce the biomass RGO has increased the number of defective sites on RGO. This is attributed to the effect of heat treatment at higher temperature through pyrolysis that has removed greater amount of oxygen‐containing groups and caused a breakage on sp 2 bond in graphene layers into sp 3 bond, leading to higher vacancy defects on the surface . The success of the synthesis of RGO was further confirmed by the XRD spectra in Figure B.…”

Thermal Stability and Potential Cycling Durability of Nitrogen-Doped Graphene Modified by Metal-Organic Framework for Oxygen Reduction Reactions

“…In the NHEW ball milling synthesis method the grinding speed and time were the main parameters that controlled the final morphology, chemical structure, and the electrochemical performance of the catalyst. Therefore, after several iterations, the optimum performance of the N-G catalyst was found after 16 h at 500 RPM [20,21]. It was found that, on increasing the grinding time, the particle size decreased and nitrogen-doping content kept on increasing, but the most advantageous grinding time for the highest current density and electron transfer number was 16 h. The N-G catalyst exhibited almost similar performance as the 10 wt % Pt/C catalyst, however, it was concluded that there was room for improvement [20].…”

“…Specifically, the nanoscale high energy wet (NHEW) ball milling method was implemented, in which the activation energy was obtained from collisions of the grinding balls and the precursor materials. Various parameters such as the grinding speed and grinding time were carefully controlled to optimize the catalyst's ORR catalytic activity [20][21][22]. The electrochemical performance (current density) of N-G/MOF catalysts was better than the 10 wt % Pt/C catalyst under similar experimental conditions [22].…”

Core-Shell Fe3O4@NCS-Mn Derived from Chitosan-Schiff Based Mn Complex with Enhanced Catalytic Activity for Oxygen Reduction Reaction

“…Therefore, efforts have been made to develop Pt alternative catalysts for ORR. In alkaline media, electrocatalysts with various categories have been developed, further, the corresponding mechanisms have been explored, including nonmetal-doped carbon materials [4][5][6][7][8], carbon-transition metal hybrids [9][10][11][12][13][14][15][16][17][18][19][20], metal organic framework-modified nitrogen-doped graphene [21][22][23], and transition metal oxides [24][25][26][27][28]. Nonmetal heteroatom doped carbon materials and transition metal oxides have especially been given attention due to their advantages of high electron conductivity and favorable redox reversibility, respectively [29,30].…”