Atomic interface regulation is thought to be an efficient method to adjust the performance of single atom catalysts. Herein, a practical strategy was reported to rationally design single copper atoms coordinated with both sulfur and nitrogen atoms in metal-organic framework derived hierarchically porous carbon (S-Cu-ISA/SNC). The atomic interface configuration of the copper site in S-Cu-ISA/SNC is detected to be an unsymmetrically arranged Cu-S 1 N 3 moiety. The catalyst exhibits excellent oxygen reduction reaction activity with a half-wave potential of 0.918 V vs. RHE. Additionally, through in situ X-ray absorption fine structure tests, we discover that the low-valent Cuprous-S 1 N 3 moiety acts as an active center during the oxygen reduction process. Our discovery provides a universal scheme for the controllable synthesis and performance regulation of single metal atom catalysts toward energy applications.

Single atomic Fe-N x moieties embedded on a high surface area carbon (Fe-N/C) represents one of the most promising nonprecious metal electrocatalysts for the oxygen reduction reaction (ORR) in polymer electrolyte membrane fuel cells. While significant progress has been made in the preparation of Fe-N/C catalysts with high-density Fe-N x sites, key structural descriptors determining the intrinsic activity of the Fe center remain elusive, and effective ways to enhance the intrinsic activity are still lacking. Moreover, most Fe-N/C catalysts developed to date are built on carbons with rather low graphitization degree, which suffer from relatively severe carbon corrosion and thereby poor stability. The direct growth of carbon nanotubes doped with high-density Fe-N x sites neighbored with graphitic-nitrogen-rich environment is reported here, which are successfully applied as a both active and stable ORR electrocatalyst in fuel cells. Combining both experiments and density functional theory calculations, it is revealed that the neighboring graphitic nitrogen can effectively induce higher filling degree of d-orbitals and simultaneously decrease on-site magnetic moment (namely, lowered spin) of the Fe center, which can optimize the binding energies of ORR intermediates and thereby substantially enhance intrinsic ORR activity.

due to their mechanical flexibility in volume and shape requirement, high power density, rapid charge/discharge rate, long cycle lifetimes, and remarkable stitchability. [1][2][3][4][5][6][7][8] However, one of the key challenges of the FSCs in the light of their practical applications is to increase their volumetric energy density to the value approaching to or even exceeding those of microbatteries without sacrificing the power density, cycle life, and other performance para meters. [9][10][11][12][13][14][15] Both the energy and power density of a SC is strongly dependent on the operating voltage, that is, V 2 (E = 1/2 CV 2 and P = V 2 /4R ESR , where C is the capacitance of the device, V is the operating voltage, and R ESR is the equivalent series resistance). [16][17][18][19][20][21][22][23][24][25] Therefore, increasing the voltage window would be an effective approach to achieve highefficiency FSCs.To this end, enormous efforts have been devoted to the fabrication of asymmetric FSCs (AFSCs) which make full utilization of the operational windows of both the positive and negative electrode materials. [25][26][27][28][29][30][31][32] Nevertheless, the intrinsic characteristic voltage of water splitting (1.23 V) means that an aqueous electrolyte is limited to a potential domain of around 1 V, thus constraining the operating voltage to a maxi mum of 1.8-2.0 V, [28][29][30][31][32][33] which is indeed lower than that of Fiber supercapacitors (FSCs) represent a promising class of energy storage devices that can complement or even replace microbatteries in miniaturized portable and wearable electronics. One of their main limitations, however, is the low volumetric energy density when compared with those of rechargeable batteries. Considering the energy density of FSC is proportional to CV 2 (E = 1/2 CV 2 , where C is the capacitance and V is the operating voltage), one would explore high operating voltage as an effective strategy to promote the volumetric energy density. In the present work, an all-solid-state asymmetric FSC (AFSC) with a maximum operating voltage of 3.5 V is successfully achieved, by employing an ionic liquid (IL) incorporated gel-polymer as the electrolyte (EMIMTFSI/PVDF-HFP). The optimized AFSC is based on MnO x @TiN nanowires@carbon nanotube (NWs@CNT) fiber as the positive electrode and C@TiN NWs@CNT fiber as the negative electrode, which gives rise to an ultrahigh stack volumetric energy density of 61.2 mW h cm −3 , being even comparable to those of commercially planar lead-acid batteries (50-90 mW h cm −3 ), and an excellent flexibility of 92.7% retention after 1000 blending cycles at 90°. The demonstration of employing the ILs-based electrolyte opens up new opportunities to fabricate high-performance flexible AFSC for future portable and wearable electronic devices.