Beta-phased Ni(OH)(2) nanowall film with reversible capacitance higher than theoretical Faradic capacitance

beta-Ni(OH)(2) was constructed into a three-dimensional mesoporous film on Ni foam with ultra-thin (similar to 6 nm) primary nanowalls showing ultrahigh specific capacitance (2675 F g(-1)) and excellent cycling performance (>96% for 500 cycles). The capacitance was higher than theoretical value possibly due to the combination of Faradic and electrical double-layer capacitances.