Cr-dopant induced crystal orientation and shape modulation in Ni2P nanocrystals for improving electrosynthesis of methanol to formate coupled with hydrogen production

Abstract

Simultaneously improving the electrochemical methanol oxidation reaction (MOR) and hydrogen evolution reaction (HER) using the electrolysis technique is a significant yet challenging task. To tackle this, we report a colloidal synthesis of Cr-dopant induced crystal orientation and shape modulation in Ni₂P nanocrystals (NCs) as an advanced bifunctional electrocatalyst for electrosynthesis of value-added formate from the MOR at the anode and hydrogen at the cathode. We demonstrate that a two-electrode overall methanol splitting (OMeS) system using Cr-doped Ni₂P nanorods (NRs) as a bifunctional catalyst can achieve a lowest voltage of 1.16 V to reach a current density of 10 mA cm⁻², compared to the cell voltage of 1.65 V for overall water splitting. Combined experimental and theoretical investigations revealed that the Cr-dopant induces shape modulation and crystal orientation in Ni₂P, which favors the thermodynamics of the dehydrogenation process in the MOR and hydrogen adsorption in the HER, leading to enhanced electrocatalytic activities. Interestingly, a proof-of-concept solar-driven system fabricated using a commercial Si photovoltaic cell integrated with an OMeS cell employing bifunctional Cr-doped Ni₂P NRs generated a stable photocurrent density of ∼12.3 mA cm⁻² for 60 min., demonstrating its promise for energy-efficient and selective electrosynthesis, enabling the production of valuable chemicals and clean hydrogen in a sustainable manner.