Light‐Induced Activation of Adaptive Junction for Efficient Solar‐Driven Oxygen Evolution: In Situ Unraveling the Interfacial Metal–Silicon Junction

Abstract

photosynthetic or solar-driven watersplitting systems, the oxygen evolution reaction (OER) is driven by a four-chargecarrier transfer pathway, while either carbon dioxide reduction or the hydrogen evolution reaction takes place on the counter electrode. However, this halfreaction (i.e., the OER) is regarded as the kinetic bottleneck for both artificial photosynthesis and overall water splitting because of the large energy requirements (i.e., large overpotentials) for driving the multielectron transfer processes. Fortunately, light-absorbing semiconductor devices that utilize small bandgap materials, such as Si, GaAs, or GaP, have been demonstrated to be efficient photoelectrodes for achieving high performance catalysis of the OER [5,6] owing to their wide absorption region in the visible light spectrum. Nevertheless, the utilization of these small band gap materials has commonly suffered from the considerable issue of their valance bands having characteristically low driving forces, thereby leading to poor transfer of the charge carriers needed for water oxidation. The dynamic behavior of the photoinduced charge-carrier separation is a critical factor for addressing both the overpotential requirement and poor driving force to effectively facilitate the transport of the excited minority carriers (i.e., holes) towardThe integration of surface metal catalysts with semiconductor absorbers to produce photocatalytic devices is an attractive method for achieving high-efficiency solar-induced water splitting. However, once combined with a photoanode, detailed discussions of the light-induced processes on metal/semiconductor junction remain largely inadequate. Here, by employing in situ X-ray scattering/ diffraction and absorption spectroscopy, the generation of a photoinduced adaptive structure is discovered at the interfacial metal-semiconductor (M-S) junction between a state-of-the-art porous silicon wire and nickel electrocatalyst, where oxygen evolution occurs under illumination. The adaptive layer in M-S junction through the light-induced activation can enhance the voltage by 247 mV (to reach a photocurrent density of 10 mA cm −2 ) with regard to the fresh photoanode, and increase the photocurrent density by six times at the potential of 1.23 V versus reversible reference electrode (RHE). This photoinduced adaptive layer offers a new perspective regarding the catalytic behavior of catalysts, especially for the photocatalytic water splitting of the system, and acting as a key aspect in the development of highly efficient photoelectrodes.

Gold Nanorod-Decorated Metallic MoS2 Nanosheets for Synergistic Photothermal and Photodynamic Antibacterial Therapy

“…Photoresponsive nanomaterials have been extensively applied for energy conversion, electronic devices, and medical therapies [1][2][3][4][5][6][7][8]. Recently, the use of light-activated nanomaterials has been focused on phototherapy [9][10][11][12][13][14][15][16].…”

Two‐Dimensional Silicon for (Photo)Catalysis

“…Despite the proliferation of the study on 2D Si catalytic performances in recent years, the understanding of 2D Si's chemistry and the approaches to exploit it are far from a developed stage, as compared with other forms of nanosilicon (including Si quantum dots, Si nanowire, porous Si, etc). [ 72 ] For example, black Si has been coupled with brilliant interfacial engineering and design of cocatalysts to achieve an efficient and stable photoelectrochemical oxygen evolution reaction, [ 72 ] whereas oxygen production was not found for 2D Si photocatalysis [10b] . This gap however, should not be considered disappointing but rather a gold mine for researchers to excavate.…”

Stabilization of NiFe Layered Double Hydroxides on n-Si by an Activated TiO2 Interlayer for Efficient Solar Water Oxidation

“…Also, our work has the specialty of forming the adaptive junction photoanode through depositing thin and amorphous NiFe (∼40 nm) and TiO 2 (5 nm) layers on n-Si which was contributed to yielding high photovoltage. 31,33,67 Because the catalysts on n-Si have high porosity, charge compensating ions can easily permeate through the films of catalysts. This phenomenon results in the larger barrier height in the junction in comparison with buried junction, leading to a lower recombination rate with the increased photovoltage and entire photoanode efficiency.…”