P-doped Co-based nanoarray heterojunction with multi-interfaces for complementary HER/OER electrocatalysts towards high-efficiency overall water splitting in alkaline

Designing electrocatalysts that can effectively couple hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) to achieve superior overall water splitting (OWS) is essential, but still a tremendous challenge. Herein, two complementary OER and HER electrocatalysts with nanoarray heterojunction (P–CoN/CWO/Co3O4/NF nanowire and P–CoN/CMO/Co3O4/NF nanosheet) were designed by combining the concepts of multi-interface engineering and element doping. Benefiting from the regulation of the electronic environment of the metal center by multi-heterointerfaces and phosphorus doping, the two electrocatalysts possess excellent OER/HER activity in 1.0 M KOH, respectively. For OER, P–CoN/CWO/Co3O4/NF exhibits an ultra-low overpotential (η10 = 175 mV) and superior long-term durability (≥80 h) at a current density of 10 mA cm−2. For HER, P–CoN/CMO/Co3O4/NF appears a desired overpotential (η10 = 109 mV) and remarkable long-term durability (≥110 h). Impressively, the P–CoN/CWO/Co3O4/NF(+)||P–CoN/CMO/Co3O4/NF(−) couple constructed with two complementary electrocatalysts exhibits outstanding OWS activity. A low cell voltage of 1.55 V in 1.0 M KOH solution can reach 10 mA cm−2, and it can operate stably at this current density for more than 96 h. The fascinating OWS activity is primarily ascribed to the complementary OER/HER activity demonstrated by the electrocatalysts at the two electrodes of the electrolytic cell, which collectively promote the kinetics of hydrolytic dissociation. This study provides a new approach to develop electrode materials for asymmetric alkaline electrolytic cells with superior overall water splitting performance.