Understanding the Roles of Nitrogen Configurations in Hydrogen Evolution: Trace Atomic Cobalt Boosts the Activity of Planar Nitrogen-Doped Graphene

Abstract

Revealing the exact roles of nitrogen configurations and precise control of the nitrogen configuration in nitrogen-doped graphene (NG) are extremely important for realizing its advanced functions in clean energy technologies. Herein, for the first time, we established that the hydrogen evolution reaction (HER) activities of NG display definite trends due to its nitrogen configurations, which were selectively generated by using layer-structured montmorillonite (MMT) with different layer distances and functions modulated by Co 2+ , Ni 2+ , Na + , and H + ions. We found that among the three types of N, i.e., pyridine, pyrrolic, and quaternary N, quaternary N is the most active one for HER in a metal-free NG catalyst, whereas with an introduction of trace atomic cobalt, the planar (pyridine and pyrrolic) N becomes the better one. In contrast, when trace atomic Ni is involved to replace the Co, the former results in heavily depressed HER activities for the NG catalyst. Density functional theory calculations further revealed that (i) the carbon atoms are highly activated for HER by the nearby quaternary N but not by planar N and (ii) nickel blocks but cobalt promotes the hydrogen adsorption after coordination with planar N, leading to an excellent HER performance.

Oxygen Reduction Reaction and Hydrogen Evolution Reaction Catalyzed by Pd–Ru Nanoparticles Encapsulated in Porous Carbon Nanosheets

“…Furthermore, all of the slope values are quite close with Pd/C, implying that a similar reaction mechanism was adopted for all of the samples. Such close Tafel slope values with Pd/C suggest that the rate-dominant step is probably the first-electron transfer to oxygen molecule, while the following reduction and the breaking of the O-O bond are relatively fast [48][49][50]. The above findings further confirm that Pd 50 Ru 50 /CNs exhibited slightly superior ORR activity than that of commercial Pd/C.…”

Atomically Dispersed Single Ni Site Catalysts for Nitrogen Reduction toward Electrochemical Ammonia Synthesis Using N2 and H2O

“…However, with increasing the pyrolysis temperature, graphitic nitrogen becomes dominant. As we reported earlier, pyridinic nitrogen content is critical for NRR activity while graphitic nitrogen is known to favor HER . Therefore, NRR activity decreased with increasing the pyrolysis temperature, which may be related to the increase of graphitic nitrogen as well as the lack of Ni‐N coordination.…”

Hollow Nanocages of NixCo1−xSe for Efficient Zinc–Air Batteries and Overall Water Splitting

“…However, the largescale commercial implementation of both Pt-based and Ru-/ Ir-based materials has been significantly hampered by their scarcity, high cost, and poor long-term durability. Therefore, it is imperative to develop Earth-abundant, cost-effective, high-efficiency, and robust electrocatalysts [12,[15][16][17][18][19][20][21][22][23][24].…”