The electronic properties of semiconducting electrocatalysts are of fundamental research interest and of great importance for oxygen evolution reaction (OER) from water splitting. Engineering the band levels is a promising route to design and fabricate nonprecious earth-abundant semiconducting electrocatalysts for OER. Herein, p-type semiconductor electrocatalysts of ultrathin nickel-cobalt inorganic-organic hydroxide hybrid nanobelts [CoxNi1-x(OH)(BzO)·H2O, x = 0, 0.2, 0.5, 0.8, 1.0, BzO: benzoate] with favorable band structures are proposed. The CoxNi1-x(OH)(BzO)·H2O with the energetically favorable flat band level and well matched p-p junction exhibit remarkable OER performances in alkaline environment. The optimal Co0.8Ni0.2(OH)(BzO)·H2O nanobelt electrocatalyst with nearly 4 nm in thickness achieves the superior OER performance, showing earlier onset potential (Eonset: 1.50 V vs RHE), smaller overpotential (η10: 319 mV) as well as significantly enhanced stability compared with those of IrO2 reference (Eonset: 1.51 V vs RHE and η10: 343 mV) and most previously reported OER electrocatalysts. This electronic engineering strategy would provide a new insight to the fundamental understanding of underlying OER mechanism as well as open a new avenue to rational design of semiconducting electrocatalysts with high performances.