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Electrochemical energy storage: The performance of MnO2 as a pseudo‐capacitive material was enhanced by doping electrodeposited MnO2 with physically deposited gold atoms (see picture). The resulting MnO2 electrodes showed an enhanced electronic conductivity and a remarkable stability under voltammetric cycling.

Nanoporous Ni with a tunable nanopore size and chemical compositions was fabricated by dealloying a Ni30Mn70 precursor alloy at various temperatures. The influence of electrochemical parameters on the formation of large-scale nanoporous Ni was systematically investigated. Different from the fabrication of nanoporous noble metals (Au, Pt and Pd), the dealloying of Ni30Mn70 includes three kinetically competitive processes: dissolution of Mn, interface diffusion of Ni and dissolution of Ni. The nanopore size and residual Mn can be tailored by controlling the dealloying time, temperature and applied potential. The as-dealloyed nanoporous Ni with a large internal surface area, excellent conductivity and naturally formed oxide surface can be directly used as a free-standing electrode for electrochemical supercapacitors with a high capacitance and excellent cycling stability.

The growing demand for sustainable and renewable green energy has stimulated extensive research into developing highperformance energy-storage and conversion devices that are primarily batteries, fuel cells, and supercapacitors. [ 1 ] Supercapacitors, also known as ultracapacitors or electrochemical capacitors, have higher power density and longer cycle life but much lower energy density than batteries and fuel cells. [2][3][4][5] Supercapacitors generally include electric double-layer capacitors (EDLC) [ 4 , 6-8 ] and pseudocapacitors. [ 9 ] Different from non-Faradic EDLC, the charge storage in pesudocapacitors occurs by a Faradic process through redox reactions at the interface between electrode and electrolyte. Thus, pseudocapacitors usually possess larger capacitance and higher energy density than do EDLC. By further improving specifi c capacitance and energy density, pseudocapacitors are expected to bridge the gap between batteries, which have high energy density but low power density, and supercapacitors, which possess high power density but low energy density. The capacitance performance of pseudocapacitors mainly depends on the active electrode materials. Metal oxides [ 10 , 11 ] and conductive polymers [ 12 , 13 ] have been widely considered as potential electrode materials for pseudocapacitors. Amongst various pseudocapacitive materials, ruthenium dioxide (RuO 2 ) has been extensively studied because of its ultralarge theoretical specifi c capacitance [ 14 , 15 ] and high metallic electrical conductivity (10 5 S cm − 1 ), as well as excellent chemical stability at room temperature. [16][17][18][19][20][21] During the charge and discharge, the electrochemical process is a reversible change in the valence state of RuO 2 (see Equation (1) ) while the protons and electrons are transferred between RuO 2 and acidic electrolytes. [ 15 ] This reaction is predicted to provide an ultrahigh specifi c capacitance (ca. 1400-2000 F g − 1 ) of RuO 2 . [22][23][24] However, such a high capacitance has not been achieved by experiment and experimental specifi c capacitances are usually much lower than the theoretical value. The poor performance of RuO 2 for charge storage has been attributed to intrinsically low electron-proton transport, serious agglomeration of RuO 2 particles, and weak conductivity between nanoparticles. [ 14 , 15 , 25-29 ] To utilize the capacitance of RuO 2 , conductive supports, such as active carbon, carbon black, carbon nanotubes, and graphene, [ 14 , 15 , 30-32 ] have been widely used to improve electron-proton transport and immobilize the active RuO 2 for high capacitance. For example, Das et al. electroplated RuO 2 onto single-walled carbon nanotubes and achieved a high capacitance of 1084 F g − 1 ; [ 14 ] Soin et al. dispersed RuO 2 on layered graphene nanofl akes and obtained a capacitance of 650 F g − 1 . [ 15 ] Although these carbon materials have good electronic conductivity, light weight, and large surface area, RuO 2 particles can only physically attach onto their surfaces and ca...

A binder-free self-grown oxy-hydroxide@nanoporous Ni-Mn hybrid electrode with high capacitance and cyclic stability is fabricated by electrochemical polarization of a dealloyed nanoporous Ni-Mn alloy. Combined with the low material costs, high electrochemical stability, and environmentally friendly nature, this novel electrode holds great promise for applications in high-capacity commercial supercapacitors.

Composition‐controlled fabrication of bimetallic catalysts is of significance in electrochemical energy conversion and storage. A novel nanoporous Pt‐Cu bimetallic catalyst with a Pt skin and a Pt‐Cu core, fabricated by electrochemically dealloying a bulk Pt‐Cu binary alloy using a potential‐controlled approach, is reported. The Pt/Cu ratio of the dealloyed nanoporous catalyst can be readily adjusted in a wide composition range by only controlling dealloying potential. The electro‐catalytic performance of the nanoporous Pt‐Cu catalyst shows evident dependence on Pt/Cu ratio although the surfaces of all the nanoporous catalysts are characterized to be covered by pure Pt. With optimal compositions, the dealloyed nanoporous Pt‐Cu catalyst possesses enhanced electrocatalytic activities toward oxygen reduction reaction and formic acid oxidation in comparison with the commercial Pt/C catalyst.

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Nanoporous gold dramatically enhances specific capacitances of PPy and MnO2, resulting in ultrahigh energy density and power density of the PPy–NPG//MnO2–NPG asymmetric supercapacitor with a wide potential window.