Morphology Engineering of Co 3 O 4 via Cetyltrimethylammonium Bromide-Mediated ZIF-67 Synthesis for Efficient Photo-Assisted Electrooxidation of Methanol

Co 3 O 4 is a promising nonprecious metal photoelectrocatalyst due to its mixed valence states (Co 2+ /Co 3+ ) and spinel structure, but the morphology–performance relationship remains unclear. Herein, morphology-engineered Co 3 O 4 was synthesized via a cetyltrimethylammonium bromide (CTAB)-directed ZIF-67 precursor route, yielding four distinct shapes (RD, TRD, NC, TC), whose formation was rationalized by molecular dynamics simulations. The inherited Co 3 O 4 morphologies were systematically correlated with photoelectrocatalytic methanol oxidation performance through multiple descriptors (surface area, pore structure, Co 3+ /Co 2+ ratio, oxygen vacancies, band gap, and •OH adsorption energy). Combined experimental and theoretical results reveal that the TRD morphology exhibits superior activity, benefiting from synergistic effects of dominant {111} facet exposure, high surface area, enriched Co 3+, abundant oxygen vacancies, narrow band gap, and efficient charge separation. Moreover, the oxidation pathway of methanol, the contribution of reactive oxygen species, and the catalyst stability are further discussed in conjunction with theoretical calculations. This work elucidates the structure–activity relationship in Co 3 O 4 photoanodes, thereby guiding the design of efficient, low-cost catalysts for photo-assisted direct methanol fuel cells (PDMFCs).