A facile approach to prepare silicon-based Pt-Ag tubular dendritic nano-forests (tDNFs) for solar-light-enhanced methanol oxidation reaction

Abstract

which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly credited.In this paper, a facile two-step Galvanic replacement reaction (GRR) is proposed to prepare Pt-Ag tubular dendritic nano-forests (tDNFs) in ambient condition for enhancing methanol oxidation reaction (MOR) under solar illumination. In the first GRR, a homogeneous layer of silver dendritic nano-forests (DNFs) with 10 μm in thickness was grown on Si wafer in 5 min in silver nitride (AgNO3) and buffer oxide etchant (BOE) solution. In the second GRR, we utilized chloroplatinic acid (H2PtCl6) as the precursor for platinum (Pt) deposition to further transform the prepared Ag DNFs into Pt-Ag tDNFs. The catalytic performance and solar response of the Pt-Ag tDNFs toward methanol electro-oxidation are also studied by cyclic voltammetry (CV) and chronoamperometry (CA). The methanol oxidation current was boosted by 6.4% under solar illumination on the Pt-Ag tDNFs due to the induced localized surface plasmon resonance (LSPR) on the dendritic structure. Current results provide a cost-effective and facile approach to prepare solar-driven metallic electrodes potentially applicable to photo-electro-chemical fuel cells.Keywords: Direct methanol fuel cell; Galvanic replacement reaction; Tubular dendritic nano-forests BackgroundDirect methanol fuel cell (DMFC) has been deemed as one of the important power suppliers for renewable power applications due to the high energy-conversion efficiency thereof [1,2]. One of the major issues of DMFCs is the slow process of methanol oxidation reaction (MOR), which directly limits the efficiency of DMFC [ 3]. Traditionally, platinum (Pt)-based alloy has been used as common a catalyst in MOR. In the past two decades, many bimetallic catalysts have been proposed to enhance the efficiency , were proposed to boost methanol oxidation under ultraviolet (UV) illumination for photo-electrochemical fuel cells [9]. Although over 60% of enhancement on MOR has been realized under UV illumination (365 nm, 100 W) [8], seldom, reports discussed the solar enhancement toward MOR, especially on pure metallic catalysts. In this paper, a facile two-step Galvanic replacement reaction (GRR) is proposed to prepare Pt-Ag tubular dendritic nano-forests (tDNFs) in ambient condition for enhancing MOR under solar illumination.In preparation of the aforementioned bimetallic catalysts, GRR was widely employed to provide a simple and cost-effective fabrication approach [10,11]. By utilizing the difference in the standard reduction potentials, replacement between two metals can be easily achieved at ambient condition. Many metal composites prepared by GRR have been reported, including Ag-Au [12,13], Pt-Au [14,15], 17], , Pd-Ag [22,23], , and Cu-Ag [25]. However, most of the studies focused on the preparation of non-supported catalysts. The prepared catalysts suspended in the solution could be hardly collected and deposited on the electrodes in the electrochemical cells. Moreover, the effective electroc...

Facile Synthesis of Bimetallic Pt-Ag/Graphene Composite and Its Electro-Photo-Synergistic Catalytic Properties for Methanol Oxidation

“…In the first illumination cycle, the current intensities were boosted from 0.325 to 2.171 (mA•cm −2 ) (568.0% increase) under UV irradiation (curve c) and from 0.325 to 1.522 (mA•cm −2 ) (368.3% increase) under visible irradiation, respectively (curve b). The increase of current density in the first illumination cycle is apparently higher than that of the reported silicon-based Pt-Ag nanoforests catalyst under visible irradiation [37]. Therefore, the as-synthesized Pt-Ag/GNs should be a more efficient Pt-Ag bimetal electro-photo synergistic catalyst for MOR under solar irradiation.…”

“…The I f /I b of Pt-Ag/GNs is 0.85 after UV irradiation for 30 min, which is higher than that of Pt/GNs (0.80) and Pt/C-JM (0.72) (Figure 7), respectively, implying more valid oxidation of methanol to carbon dioxide during the anodic scan and the removal of poisoning species from the surface of Pt-Ag/GNs under UV irradiation. It should be noted that Pt-Ag/GNs not only exhibited better catalytic activity, stability and tolerance to CO under UV irradiation, but its visible light assisted electro-photo synergistic catalysis performance is also more effective than that of the reported silicon-based Pt-Ag nano-forests catalyst [37]. The efficient synergistic catalysis under UV and visible light irradiation is in favor of harvesting the natural sunlight (UV and visible light) to produce clean energy and provides very promising practical applications.…”

State of the art of nanoforest structures and their applications

“…22) at r.t. and applied in a cost-effective methanol oxidation reaction under solar irradiation. 108 The rst step was the growth of Ag nanoforests (10 mm in thickness) on a silicon wafer in AgNO 3 solution, and then H 2 PtCl 6 was used as a precursor for Pt deposition, converting the silver dendritic nanoforests into Pt-Ag tDNFs. The observed solar response (6.4% enhancement of the oxidation current) was attributed to the strong LSPR due to the Ag DNFs, so this material can be used in photo-electrochemical fuel cells.…”