Solar-driven methanol to formate conversion coupled with energy-efficient hydrogen production through Cr dopant-induced charge transfer modulation at the in-situ formed FeOOH/FeCo-LDHs interface

Abstract

The goal of developing efficient electrocatalysts that can effectively accelerate both the hydrogen evolution reaction (HER) and the methanol oxidation reaction (MOR) is essential. Additionally, overcoming the sluggish anodic oxygen evolution reaction (OER) also presents a considerable challenge for achieving energy-efficient hydrogen (H2) production. Herein, we report the synthesis of self-supported hierarchical FeOOH/Fe0.5CoCr0.5LDHs as an advanced electrocatalyst by employing simultaneous engineering strategies for producing the formate from MOR at the anode while simultaneously generating H2 at the cathode. Both the experimental and theoretical studies demonstrate the superior charge transfer enabled by the in-situ formed heterostructure. Additionally, electronic modulation due to Cr intercalation, and the presence of a superhydrophilic hybrid surface morphology promote the remarkable electrocatalytic activity and stability of the FeOOH/Fe0.5CoCr0.5-LDHs electrocatalyst. The overall water splitting process required a cell voltage of 2.01 V to achieve a current density of 50 mA cm- 2, whereas a lower cell voltage of 1.76 V was sufficient for overall methanol oxidation. Remarkably, a solar-driven system prototype, consisting of a commercial Si cell combined with a methanol splitting electrolyzer comprising FeOOH/Fe0.5CoCr0.5-LDHs electrodes, achieved a photocurrent density of 8.1 mA cm-2 over 2 h. This work demonstrates the capability of earth-abundant elements-based electrocatalysts for sustainable and selective electrochemical synthesis. As a result, it enables the energy-efficient generation of clean H2 and valuable chemicals byproducts.