Synergetic effect of nitrogen‐doped carbon catalysts for high‐efficiency electrochemical CO_(2) reduction

The use of carbon‐based materials is an appealing strategy to solve the issue of excessive CO_(2) emis‐sions.In particular,metal‐free nitrogen‐doped carbon materials(mf‐NCs)have the advantages of convenient synthesis,cost‐effectiveness,and high conductivity and are ideal electrocatalysts for the CO_(2) reduction reaction(CO_(2)RR).However,the unclear identification of the active N sites and the low intrinsic activity of mf‐NCs hinder the further development of high‐performance CO_(2)RR electrocat‐alysts.Achieving precise control over the synthesis of mf‐NC catalysts with well‐defined active N‐species sites is still challenging.To this end,we adopted a facile synthesis method to construct a set of mf‐NCs as robust catalysts for CO_(2)RR.The resulting best‐performing catalyst obtained a Far‐adaic efficiency of CO of approximately 90%at−0.55 V(vs.reversible hydrogen electrode)and good stability.The electrocatalytic performance and in situ attenuated total reflectance surface‐enhanced infrared absorption spectroscopy measurements collectively revealed that graphitic and pyridinic N can synergistically adsorb CO_(2) and H_(2)O and thus promote CO_(2) activation and protonation.

Transition metal-nitrogen sites for electrochemical carbon dioxide reduction reaction

Electrochemical CO2 reduction reaction(CO2RR)powered by renewable electricity has emerged as the most promising technique for CO2 conversion,making it possible to realize a carbon‐neutral cycle.Highly efficient,robust,and cost‐effective catalysts are highly demanded for the near‐future practical applications of CO2RR.Previous studies on atomically dispersed metal‐nitrogen(M‐Nx)sites constituted of earth abundant elements with maximum atom‐utilization efficiency have demonstrated their performance towards CO2RR.This review summarizes recent advances on a variety of M‐Nx sites‐containing transition metal‐centered macrocyclic complexes,metal organic frameworks,and M‐Nx‐doped carbon materials for efficient CO2RR,including both experimental and theoretical studies.The roles of metal centers,coordinated ligands,and conductive supports on the intrinsic activity and selectivity,together with the importance of reaction conditions for improved performance are discussed.The mechanisms of CO2RR over these M‐Nx‐containing materials are presented to provide useful guidance for the rational design of efficient catalysts towards CO2RR.

Oxygenated boron-doped carbon via polymer dehalogenation as an electrocatalyst for high-efficiency O_(2)reduction to H_(2)O_(2)

The direct electrochemical synthesis of H_(2)O_(2)from O_(2)is currently the most promising alternative to energyintensive industrial anthraquinone oxidation/reduction methods. However, its widespread use is hampered by the lack of efficient low-cost electrocatalysts. In the current study,oxygenated boron-doped carbon(O-BC) materials were realized via a green synthetic strategy involving polymer dehalogenation and employed as electrode materials for the electrochemical synthesis of H_(2)O_(2)via a 2 e-oxygen reduction.The catalytic activity of the O-BC materials was optimized through systematic variation of the boron source(H_(2)BO_(2))dosage and annealing temperature. Electrochemical measurements revealed that the optimal sample(O-BC-2-650)exhibited a selectivity of 98% for the 2 e-oxygen reduction to H2 O_(2)and an average H_(2)O_(2)production rate of412.8 mmol g_(cat)^(-1) h^(-1)in an H-type alkaline electrolyzer. Density functional theory simulations indicated that the functionalization of active B sites with one oxygen atom provides the lowest Gibbs free energy change(ΔG) of 0.03 e V for the hydrogenation of*O_(2), while functionalization with zero or two O atoms results in much larger ΔG values(0.08 and 0.10 e V,respectively). Thus, this work details a new type of green, lowcost, and metal-free electrocatalyst for H_(2)O_(2)production.

Highly nitrogen and sulfur dual-doped carbon microspheres for supercapacitors

Heteroatom doping, especially dual-doped carbon materials have attracted much attention for the past few years, and have been regarded as one of the most efficient strategies to enhance the capacitance behavior of porous carbon materials. In this work, a facile two-step synthetic route was developed to fab- ricate nitrogen and sulfur co-doped carbon microsphere （NSCM） by using thiourea as dopant. The NJS doping content is controlled via varying the carbonization temperature. It has been proved that a suitable quantity of N and S groups could not only provide pseudo-capacitance but also promote the electron transfer for carbon materials, which ensures the further utilization of the exposed surfaces for charge storage. The optimized NSCM prepared at a carbonization temperature of 800 ℃ （NSCM-800） achieves a capacitance of 277.1 F g^-1 at a current density of 0.3 A g^-1 in 6.0 mol L^-1 KOH electrolyte, which is 71% higher than that of undoped carbon microsphere. Besides, NSCM-800 shows an excellent cycling stability, 98.2% of the initial capacitance is retained after 5,000 cvcles at a current densitv of 3.0 A g^-1.