激光熔覆-电化学脱合金制备Ti/TiO2光阳极:多孔层厚度对其光催化性能的影响OA

Semiconductor photocatalysis represents a promising and sustainable strategy for addressing global energy shortages and environmental pollution.Among various candidates,Titanium Dioxide(TiO2)has garnered extensive attention due to its excellent chemical stability,non-toxicity,and cost-effectiveness.However,the practical application of bulk TiO2 is severely limited by its low specific surface area and the rapid recombination of photogenerated electron-hole pairs.While constructing nanoporous structures is an effective strategy to overcome these limitations,conventional fabrication methods often suffer from poor substrate adhesion or difficulties in precisely controlling structural parameters.In particular,the thickness of the active porous layer,a critical dimension determining light absorption paths and charge transport distances,has rarely been investigated as an independent variable.To address these challenges,this study proposes a novel composite fabrication strategy combining laser cladding with electrochemical dealloying,aiming to systematically investigate the quantitative structure-property relationship between the thickness of the nanoporous Ti/TiO2 layer and its photoelectrochemical/photocatalytic performance,thereby providing a theoretical basis for the rational design of high-performance photoanodes. In the experimental phase,Cu-Ti alloy precursor coatings with a specific composition of Cu67Ti33 are fabricated on pure titanium substrates by laser cladding.This high-energy processing method ensures a robust metallurgical bond between the functional layer and the substrate,effectively minimizing interfacial contact resistance compared with physical adhesion methods.Subsequently,the samples undergo selective electrochemical dealloying in a 20wt.％HNO3 electrolyte.In this process,Cu acts as the sacrificial component,while Ti serves as the stable scaffold;as Cu dissolves,the remaining Ti atoms self-assemble into a porous skeleton and are in-situ oxidized to form TiO2.By precisely regulating the dealloying duration(1-40 h),control over the porous layer thickness is achieved,ranging from～50 μm to over 260 μm.Microscopic morphology and elemental distribution are comprehensively characterized via SEM and EDS.Furthermore,photoelectrochemical properties and photocatalytic activity are rigorously evaluated by instantaneous photocurrent response,Electrochemical Impedance Spectroscopy(EIS),double-layer capacitance(Cdl)measurements,and methyl orange(MO)degradation tests. Morphological analysis reveals that dealloying generates a distinctive three-dimensional bicontinuous nanoporous network with a hierarchical gradient pore distribution,which facilitates electrolyte infiltration.The porous layer thickness exhibits a non-monotonic trend:it increases initially with time,peaking at～260.8 μm for the 8-hour sample,before decreasing significantly due to structural delamination and collapse at prolonged durations(16-40 h).The sample dealloyed for 8 h(npT-8 h)demonstrates optimal performance,exhibiting the highest instantaneous photocurrent density(4.54 μA/cm2),the lowest charge transfer resistance(Rct=47.28 Ω·cm2),and the largest electrochemically active surface area(Cdl=5.53 mF/cm2).In contrast,thinner films(e.g.,npT-4 h)suffer from insufficient active sites,while thicker,delaminated films show increased recombination losses.Consequently,npT-8 h achieves a 61％MO degradation rate within 180 min,with a pseudo-first-order rate constant(k=0.005 29 min-1)approximately 4.3 times that of the npT-4 h sample.The superior performance of npT-8 h is attributed to a synergistic balance achieved at this specific thickness(～260.8 μm),representing an optimal equilibrium where charge separation/transport efficiency and surface reactivity are effectively balanced,further assisted by the light-trapping effect of the porous network.This work demonstrates the feasibility of the laser cladding-dealloying route for fabricating robust porous electrodes and clarifies the underlying mechanism of thickness-dependent performance optimization.