Revealing the Effect of Anion Regulation in NiCo₂X₄ (X = O, S, Se, Te) on Photoassisted Methanol Electrocatalytic...

Designing nonprecious metal anode catalysts for photoassisted direct methanol fuel cells (PDMFCs) remains a challenge. As a semiconductor catalyst with a spinel structure, NiCo₂O₄ has good methanol catalytic oxidation activity and photocatalytic activity, making it a highly promising anode non-noble metal catalyst for PDMFCs. However, compared with the noble metal catalyst, the photoelectrocatalytic activity remained to be improved. In this report, an anion regulation strategy was adopted to improve the photoassisted methanol electrocatalytic activity. Using a CoNi-Aspartic (CoNi-Asp) nanorod as the precursor, the anion-regulated NiCo₂X₄ (X = O, S, Se, Te) was prepared by oxidation, sulfuration, selenization, and telluridation reactions. The regulation of anions and their effects on the electronic structure, intermediate product, and photoelectric catalytic performance of NiCo₂X₄ (X= O, S, Se, Te) was systematically discussed. Photoelectrochemical characterization and adsorption energy of ^•OH revealing the volcano-like correlation between the anion in NiCo₂X₄ (X = O, S, Se, Te) and their photoelectrocatalytic performance. The narrowest band gap (2.239 eV), the highest ^•OH adsorption energy (-3.32 eV), and the highest ratio of Co³⁺/Co²⁺ (2.19) ensure the best photoelectric catalytic performance of NiCo₂S₄, under the visible light irradiation, the photoresponse current density was 1.9 A g^-1, the current density at 0.6 V was up to 21.9 A g^-1_. After 9 h of stability testing, the current retention rate was 80%. This report sheds an idea for the rational design of non-noble anode catalysts for PDMFCs.