Highly efficient photoelectrochemical (PEC) hydrogen production is achieved using p-Si wire arrays loaded with NiMoZn particles in aqueous sulfuric acid under simulated sunlight (AM 1.5 G; 100 mW cm(-2)). Vertically-aligned wire arrays are grown on planar Si wafers via a quick electroless etching process within 5 min, leading to short Si wires of similar to 4 mu m and diameters of similar to 0.2 mu m. Despite the short length of the wires, the reflectance of the arrays is <5% over the wavelength range of 400-800 nm (the reflectance of planar Si is similar to 40%) and the photocurrent density (I-ph) is enhanced by similar to 30% relative to planar Si. To further improve the PEC performance, similar to 100nm NiMoZn particles are photoelectrochemically deposited onto the wires. The wire arrays with evenly distributed NiMoZn particles show a photocurrent onset potential (E-on) of similar to+0.27V vs. RHE and produce an I-ph of similar to 1.45 mA cm(-2) at OV vs. RHE with a Faradaic efficiency of similar to 100% for H-2 evolution. This I-ph value is similar to 10-fold greater than that with the planar Si/NiMoZn samples. The excellent performance of the wire arrays and NiMoZn heterojunction is attributed to enhanced light absorption (decreased reflectance), facilitated charge transfer (radial-directional electron transfer), and NiMoZn-catalyzed hydrogen production. (C) 2017 Elsevier B.V. All rights reserved.