Amino-tethered Ni₃S₂/MoS₂ heterojunction for coupling electrochemical 5-hydroxymethylfurfural oxidation with 4-nitrophenol hydrogenation

Paired electrocatalytic systems have emerged as a promising approach for the synthesis of high value-added fine chemicals from renewable resources such as biomass, however, a high-performance bifunctional catalyst is urgently needed to reduce overall cell voltage and enhance faradaic efficiency. Herein, an amino-tethered Ni₃S₂/MoS₂ heterojunction (NiMoS_x-NH₂) was constructed as a bifunctional catalyst for simultaneous anodic 5-hydroxymethylfurfural oxidation into furan dicarboxylic acid and cathodic 4-nitrophenol hydrogenation into p-aminophenol, providing a high conversion, yield, and faradaic efficiency above 98% on both electrodes. On the one hand, the amino-tethered Ni₃S₂/MoS₂ heterojunction accelerated electron transfer, and on the other hand, it promoted the catalysts' proton-coupled electron-transfer process to generate Ni^III-O(OH)_ad at the anode and H* desorption at the cathode. A highly efficient paired electrolyzer with NiMoS_x-NH₂ as a bifunctional catalyst was then assembled demonstrating an extremely low cell voltage of 0.89 V at 10 mA cm⁻², whereas the sum of the faradaic efficiency for FDCA and 4-AP was ∼200% at 1.75 V for the overall reaction.