Towards a fundamental understanding of heterogeneous iron oxide-oxalate system: The enhanced interfacial electron transfer

• The absorbed oxalate on hematite could act as bridge to promote the interfacial electron transfer . • {0 1 2} facets of hematite could adsorb more oxalate than other facets due to their special structures. • Heterogeneous iron oxide-oxalate systems contribute more than as expected in nature.