Abstract

Downsizing metal nanoparticles into nanoclusters and single atoms represents a transformative approach to maximizing atom utilization efficiency for energy applications. Herein, a bovine serum albumin-templated synthetic strategy is developed to fabricate iron and nickel nanoclusters, which are subsequently hydrothermally composited with graphene oxide. Through KOH-catalyzed pyrolysis, the downsized metal nanoclusters and single atoms are embedded in a hierarchically porous protein/graphene-derived carbonaceous aerogel framework. The carbon-supported Fe subnanoclusters (FeSNC) as the negative electrode and Ni subnanoclusters (NiSNC) as the positive electrode exhibit remarkable specific capacitance (capacity) values of 373 F g−1 (93 mAh g−1) and 1125 F g−1 (101 mAh g−1) at 1.0 A g−1, respectively. Assembled into a supercapacitor-battery hybrid configuration, the device achieves an excellent specific energy (47 W h kg−1) and superior specific power (18 kW kg−1), while maintaining outstanding cycling stability of over 12 000 cycles. Moreover, FeSNCs displayed a significantly reduced oxygen evolution overpotential (η10 = 270 mV), outperforming the RuO2 benchmark (η10 = 328 mV). Molecular dynamics simulations, coupled with density functional theory calculations, offer insights into the dynamic behavior and electronic properties of these materials. This work underscores the immense potential of metallic subnanoclusters for advancing next-generation energy storage and conversion technologies.