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Ammonia (NH₃) electrosynthesis gains significant attention as NH₃is essentially important for fertilizer production and fuel utilization. However, electrochemical nitrogen reduction reaction (NRR) remains a great challenge because of low activity and poor selectivity. Herein, a new class of atomically dispersed Ni site electrocatalyst is reported, which exhibits the optimal NH₃yield of 115 µg cm⁻²h⁻¹at –0.8 V versus reversible hydrogen electrode (RHE) under neutral conditions. High faradic efficiency of 21 ± 1.9% is achieved at ‐0.2 V versus RHE under alkaline conditions, although the ammonia yield is lower. The Ni sites are stabilized with nitrogen, which is verified by advanced X‐ray absorption spectroscopy and electron microscopy. Density functional theory calculations provide insightful understanding on the possible structure of active sites, relevant reaction pathways, and confirm that the Ni‐N₃sites are responsible for the experimentally observed activity and selectivity. Extensive controls strongly suggest that the atomically dispersed NiN₃site‐rich catalyst provides more intrinsically active sites than those in N‐doped carbon, instead of possible environmental contamination. This work further indicates that single‐metal site catalysts with optimal nitrogen coordination is very promising for NRR and indeed improves the scaling relationship of transition metals.

 

FeN₄moieties embedded in partially graphitized carbon are the most efficient platinum group metal free active sites for the oxygen reduction reaction in acidic proton‐exchange membrane fuel cells. However, their formation mechanisms have remained elusive for decades because the Fe−N bond formation process always convolutes with uncontrolled carbonization and nitrogen doping during high‐temperature treatment. Here, we elucidate the FeN₄site formation mechanisms through hosting Fe ions into a nitrogen‐doped carbon followed by a controlled thermal activation. Among the studied hosts, the ZIF‐8‐derived nitrogen‐doped carbon is an ideal model with well‐defined nitrogen doping and porosity. This approach is able to deconvolute Fe−N bond formation from complex carbonization and nitrogen doping, which correlates Fe−N bond properties with the activity and stability of FeN₄sites as a function of the thermal activation temperature.

 

Nickel and nitrogen co-doped carbon (Ni–N–C) has emerged as a promising catalyst for the CO 2 reduction reaction (CO 2 RR); however, the chemical nature of its active sites has remained elusive. Herein, we report the exploration of the reactivity and active sites of Ni–N–C for the CO 2 RR. Single atom Ni coordinated with N confined in a carbon matrix was prepared through thermal activation of chemically Ni-doped zeolitic imidazolate frameworks (ZIFs) and directly visualized by aberration-corrected scanning transmission electron microscopy. Electrochemical results show the enhanced intrinsic reactivity and selectivity of Ni–N sites for the reduction of CO 2 to CO, delivering a maximum CO faradaic efficiency of 96% at a low overpotential of 570 mV. Density functional theory (DFT) calculations predict that the edge-located Ni–N 2+2 sites with dangling bond-containing carbon atoms are the active sites facilitating the dissociation of the C–O bond of the *COOH intermediate, while bulk-hosted Ni–N 4 is kinetically inactive. Furthermore, the high capability of edge-located Ni–N 4 being able to thermodynamically suppress the competitive hydrogen evolution is also explained. The proposal of edge-hosed Ni–N 2+2 sites provides new insight into designing high-efficiency Ni–N–C for CO 2 reduction. 

Recently, graphene fibers derived from wet-spinning of graphene oxide (GO) dispersions have emerged as viable electrodes for fiber-shaped supercapacitors (FSCs) and/or batteries, wherein large surface area, high electrical conductivity, and sufficient mechanical strength/toughness are desired. However, for most fiber electrodes reported so far, compromises have to be made between energy-storage capacity and mechanical/electrical performance, whereas a graphene fiber with high capacity and sufficient toughness for direct machine weaving or knitting is yet to be developed. Inspired by the alum mordant used for natural dyes in the traditional textile dyeing industry, our research group has synthesized wet-spun GO fibers and coagulated them with different multivalent cations ( e.g. Ca 2+ , Fe 3+ , and Al 3+ ), where dramatically different fiber morphologies and properties have been observed. The first principles density functional theory has been further employed to explain the observed disparities via cation–GO binding energy calculation. When assembled into solid-state FSCs, Al 3+ -based reduced GO (rGO) fibers offer excellent stability against bending, and a specific capacitance of 148.5 mF cm −2 at 40 mV s −1 , 1.4, 4.8, and 6.8 times higher than that of the rGO fibers based on other three coagulation systems (Fe 3+ , Ca 2+ and acetic acid), respectively. The volumetric energy density of the Al 3+ -based FSC is up to 13.26 mW h cm −3 , while a high power density of 250.87 mW cm −3 is maintained.