Bimodal nanoporous silver fabricated from dual-phase Ag10Zn90 precursor via electrochemical dealloying for direct ammonia-borane electrooxidation

Bimodal nanoporous silver (BNPS) nanoarchitectures with surface area of about 17.6 m2 g−1 have been facilely fabricated by potentiostatic dealloying of dual-phase Ag10Zn90 precursor alloys consisting of both η-Zn and ε-AgZn3 phases in alkaline solutions. The bimodal porous nanoarchitectures consisting of submicro-sized pores with characteristic sizes of about 750 nm and nano-sized nanopores with a size of about 9 nm are resulted from the primary selective dissolution of η-Zn phases and subsequent dealloying of ε-AgZn3 phases. BNPSs exhibit superior electrocatalytic capabilities for the direct oxidation of ammonia-borane (AB) with an ultralow onset potential of −195 mV vs. RHE, oxidation current densities as high as 17.27 mA cm−2 in 5 mM AB in 0.1 M NaOH and the number of electron transfers of 5.4 at 0.4 V vs. RHE close to the theoretical value of 6. The excellent catalytic activities can be attributed to the bimodal channel distributions of BNPS, in which the ultrafine nanopores provide large active surface areas for catalytic reactions, and the submicro-sized channels ensure fast mass transport for the electrocatalysis and bulk solutions.