Hydrogenated ZnO Core–Shell Nanocables for Flexible Supercapacitors and Self-Powered Systems

Abstract

Although MnO2 is a promising material for supercapacitors (SCs) due to its excellent electrochemical performance and natural abundance, its wide application is limited by poor electrical conductivity. Inspired by our results that the electrochemical activity and electrical conductivity of ZnO nanowires were greatly improved after hydrogenation, we designed and fabricated hydrogenated single-crystal ZnO@amorphous ZnO-doped MnO2 core-shell nanocables (HZM) on carbon cloth as SC electrodes, showing excellent performance such as areal capacitance of 138.7 mF/cm(2) and specific capacitance of 1260.9 F/g. Highly flexible all-solid-state SCs were subsequently assembled with these novel HZM electrodes using polyvinyl alcohol/LiCl electrolyte. The working devices achieved very high total areal capacitance of 26 mF/cm(2) and retained 87.5% of the original capacitance even after 10 000 charge/discharge cycles. An integrated power pack incorporating series-wound SCs and dye-sensitized solar cells was demonstrated for stand-alone self-powered systems.

α-Fe2O3-Based Core-Shell-Nanorod–Structured Positiveand Negative Electrodes for a High-Performance α-Fe2O3/C//α-Fe2O3/MnOxAsymmetric Supercapacitor

“…6f, whereas, at the same load current, the volumetric capacitance value is about 1.11 F/cm 3 and the specific capacitance is 100.4 F/g for α-Fe 2 O 3 //α-Fe 2 O 3 /MnO x ASC, which are also higher than those reported for other ASCs at similar load currents. 6,11,[38][39][40] Besides the α-Fe 2 O 3 /C//α-Fe 2 O 3 /MnO x ASC exhibits good rate capability with 67% retention of volumetric capacitance as compared to 52.5% retention for α-Fe 2 O 3 //α-Fe 2 O 3 /MnO x ASC when the load current increases from 0.5 mA to 7 mA, which can be ascribed to the unique nano-architectured electrode with large surface area together with high electrical conductivity for carbon shell and CC substrate promoting abundant ion adsorption as well as easy ion intercalation/deintercalation and fast charge transport at higher load currents. This observation is further supported from electrochemical impedance data and corresponding Nyquist plots for the ASCs as shown in Fig.…”

Ultrahigh‐Power Pseudocapacitors Based on Ordered Porous Heterostructures of Electron‐Correlated Oxides

“…The high electron transport pathway by interconnective V 2 O 3 network and the fast ion transport channels by the interpenetrating nanopores facilitate the charge/discharge processes in of the NP V 2 O 3 /MnO 2 electrodes at a pseudo‐constant rate over the voltammetric cycles. Therein, the entire constituent MnO 2 layer sandwiched between highly conductive ion and electron transport pathways participates in the processes of both the surface electrosorption of Na + cations and the fast, reversible surface redox reaction, i.e., MnO 2 + a H + + b Na + + ( a + b )e − ↔ MnOOH a Na b 1, 2, 3, 15, 20, 52. The enhanced pseudocapacitive behavior is further confirmed by comparison of electrochemical impedance spectroscopy (EIS) spectra for NP V 2 O 3 /MnO 2 electrodes before and after heat treatments (Figure 3b, and Figure S10b in the Supporting Information).…”

“…These advantageous features enlist pseudocapacitors to be attractive alternatives or complements to batteries for many high‐power applications in hybrid electric vehicles, portable electronic devices and renewable energy 1, 2, 3, 4, 8, 9, 13. However, conventional pseudocapacitors made from state‐of‐the‐art electrode materials, typically transition‐metal oxides (TMOs) such as MnO 2 ,5, 15, 19, 20 TiO 2 ,6, 16 and Co 3 O 4 ,19, 21 often exhibit much lower power capability than EDLCs due to their intrinsically poor conductivity 15, 21. It thus remains a primarily challenge in realizing high‐power and high‐energy densities in pseudocapacitors, which requires pseudocapacitive electrode materials simultaneously providing large specific surface area and ultrahigh transports of ions and electrons 22, 23, 24.…”

Modifying oxide nanomaterials’ properties by hydrogenation

“…[81,[84][85][86][87][88][89][90][91][92] Here, only some recent works are given as examples. Similar to hydrogenation on TiO 2 , hydrogenation introduces visible-light absorption, [86] oxygen vacancies, [86] zinc vacancies, [86,91] interstitial hydrogen, [84,85] and increased carrier densities.…”