Anion-induced vacancy enhances Co3Se4/Fe3Se4 heterostructures for high-efficiency hydrogen production

Modulation of the electronic structure of the active site by defect engineering and heterostructure are effective strategies to improve the electrocatalytic performance of catalysts. Herein, S-doped Co3Se4/Fe3Se4 (S-Co3Se4/ Fe3Se4) heterostructures derived from CoFe-layered double hydroxide (CoFe-LDH) with unique nanowirenanosheet array structures have been constructed using the different solubility product (Ksp) between sulfides and selenides. The intrinsic mechanism of their excellent electrocatalytic performance has been investigated. The unique nanowire-nanosheet array structure increases the number of exposed active sites, and the doping of sulfur not only adjusts the electronic structure of Co but also induces the enhancement of the selenium vacancy and conductivity. S-Co3Se4/Fe3Se4 exhibits excellent oxygen evolution reaction (OER) performance in 1 M KOH, requiring an overpotential of 255 mV to achieve the current density of 100 mA/cm2. With the assistance of the methanol oxidation reaction (MOR), the current density of 10 mA/cm2 is achieved with only 1.48 V while generating high-value formic acid and reducing energy consumption by 10 % relative to conventional electrocatalysts. The main active sites of the OER process have been identified by after OER characterization at the same time, which enriches the OER mechanism study. It provides the feasible strategy for tuning the electronic structure of heterostructures, and the practical reference for the development of OER and MOR bifunctional electrocatalysts.