Surface Microenvironment Optimization Induced Robust Oxygen Reduction
for Neutral Zinc-Air Batteries
Abstract
Neutral zinc-air batteries (ZABs) are promising candidates for the
next-generation power devices with considerably elongated lifetime
comparing to conventional alkaline ZABs. However, neutral cathodic
oxygen reduction reaction is seriously limited by the mass transfer
efficiency of hydroxyl due to insufficient interfacial chemical
potential-gradient between catalytic layer and electrolyte. Herein, we
highlight that electrochemical oxidation induced surface
microenvironment optimization could realize optimal chemical
potential-gradient around catalytic sites and bring outstanding neutral
ORR activity. The electro-deposited sub-nano Pt decorated
surface-microenvironment-optimized Co2N samples (denoted as Pt-SMO-Co2N
NWs) possessed 92 mV and 365 mV lower overpotential than commercial Pt/C
and pristine Co2N in 0.2 M PBS. As for neutral ZABs, Pt-SMO-Co2N NWs
cathode delivers a power density of 67.9 mW*cm−2 and displays negligible
decay after nearly 80 hours stability test at 20 mA*cm-2. In depth
characterization proposes that remarkable performance improvement
originates from optimized microenvironment which increases the surface
chemical potential gradient and facilitates proton coupled electron
transfer during ORR. We anticipated that such synergetic optimization of
microenvironment and intrinsic activity of active sites is an effective
strategy which may be extended the catalytic reactions beyond ORR.