Anion exchange membrane water electrolysis enhanced by reverse electron redistribution caused by La introduction

The built-in electric field (BIEF) formed by the rational hetero coupling of heterogeneous catalysts can reconstruct the electron distribution for efficient anion exchange membrane water electrolysis (AEMWE). However, the Schottky barrier caused by the Fermi-level difference prevents the adsorption performance of reaction intermediates in Mott-Schottky heterojunctions. Herein, a Schottky-based Ohmic contact of La 5 Mo 4 O 16 -Co 2 P with a tunneling effect is designed by conventional hydrothermal and annealing methods. The UPS, in situ ATR-FTIR, and DFT calculations reveal the role of inducing La elements: i) pump electrons to Co 2 P-bulk to inhibit the original excessive oxidation, thus improving the electron transfer efficiency, forming Ohmic contact and a reversed BIEF for higher charge density at the hetero interface; ii) induces Co 2 P with lower adsorption energies of reaction intermediates for both HER (*H) and OER (*OH, *O, and *OOH). Due to the above contributions, the La 5 Mo 4 O 16 -Co 2 P possesses a bifunctional water electrolysis performance with low overpotentials of 139.9/191.0 mV and 200.5/215.6 mV for hydrogen and oxygen evolution reactions (HER and OER) at ± 100 mA cm −2 and ± 500 mA cm −2 respectively and stable durability of 100 h. Impressively, the AEMWE with La 5 Mo 4 O 16 -Co 2 P as both the anode and cathode electrodes exhibit a cell voltage of 2.4 V better than that of 2.6 V for Pt/C-IrCo. This work proposes new sights to optimize the BIEF and promote the heterogeneous coupling for the next generation of superior bifunctional water electrolytic catalysts. • The introduction of La transforms Mott-Schottky heterojunction to Schottky-based Ohmic contact. • This reverses electron redistribution at the heterointerface with higher electron transfer efficiency. • DFT calculation and in-situ ATR-FTIR indicate easier oxygen intermediates adsorption process and RDS. • The as-obtained La 5 Mo 4 O 16 -Co 2 P exhibits outstanding bifunctional water electrolysis performance. • The AEMWE expressed better performance than PtC (cathode)/IrCo (anode).