Heterojunction engineering via in-situ electrochemical reconstruction for boosting electrocatalytic biomass upgrading-coupled hydrogen production

Rationally designing and constructing high-performance electrocatalysts is critical for environmental and sustainable electrocatalytic biomass upgrading coupled with hydrogen evolution. Herein, we developed a novel in-situ electrochemical reconstruction strategy to fabricate heterostructured electrocatalysts for efficient biomass upgrading-coupled hydrogen production. Through in-situ anodic and cathodic electrochemical reconstructions, Ni(OH)2-CuO nanorods assembled by nanosheets with abundant low-crystalline Ni(OH)2/crystalline CuO heterojunctions on Cu foam (Ni(OH)2-CuO/CF) and S-doped Ni(OH)2-Cu2O nanofoam formed by cross-linked nanoparticles on CF (Ni(OH)2-Cu2O(S)/CF) were respectively constructed for electrocatalytic 5-hydroxymethylfurfural oxidation reaction (HMFOR) and hydrogen evolution reaction (HER). For the Ni(OH)2-CuO/CF, the overall configuration of nanorods assembled by self-standing nanosheets ensures good conductivity, full exposure of active sites, and fast mass/electron transfer. The abundant Ni(OH)2/CuO heterojunctions provide dual active sites of Ni and Cu to simultaneously adsorb and activate hydroxyl and aldehyde groups in HMF. The electronic interaction between Ni(OH)2 and CuO accelerates the reversible conversion of Ni2+↔Ni3+ to generate more Ni3+ active species and enhances the intrinsic activity of dual active sites to reduce the reaction energy barrier of the rate-determining step. As a result, the Ni(OH)2-CuO/CF shows superior HMFOR performance, with a HMF conversion of 99.3%, a FDCA yield of 98.1%, and stability for 50 cycles in 10 mM HMF+1.0 M KOH medium. Meanwhile, the Ni(OH)2-Cu2O(S)/CF also exhibits remarkable HER activity with an overpotential of only 64.7 mV at 10 mA cm−2 in 1.0 M KOH solution due to its unique structure and composition. When coupling a two-electrode system, the HMFOR-HER system achieves a current density of 10 mA cm−2 at 1.44 V, 221 mV lower than that of the OER-HER system. This work provides an in-situ electrochemical reconstruction strategy for designing advanced heterojunction-rich electrocatalysts for various electrocatalytic applications.