Abstract:Unraveling
the charge-carrier dynamics at electrocatalyst/electrode
interfaces is critical for the development of efficient photoelectrochemical
(PEC) water oxidation. Unlike the majority of photoanodes investigated
for PEC water oxidation, the integration of electrocatalysts with
CuWO4 electrodes generally results in comparable or worse
performance compared to the bare electrode. This is despite the fact
that the surface state recombination limits the water oxidation efficiency
with CuWO4 electrodes, and an e… Show more
“…This value is in line with previous records for CuWO 4 -based electrodes prepared with different synthetic strategies ( Table 2 ). 41 , 42 However, it is far from the maximum photocurrent expected for the 2.2 eV band gap of CuWO 4 . Indeed, assuming that all absorbed photons in the CuWO 4 :580 electrode ( Figure 2 D) are completely converted into current would lead to a 5.6 mA cm –2 theoretical maximum photoresponse under 1 sun illumination.…”
CuWO 4 is a ternary semiconductor oxide with excellent visible light harvesting properties up to 550 nm and stability at high pH values, which make it a suitable material to build photoanodes for solar light conversion to hydrogen via water splitting. In this work, we studied the photoelectrochemical (PEC) performance of transparent CuWO 4 electrodes with tunable light absorption and thickness, aiming at identifying the intrinsic bottlenecks of photogenerated charge carriers in this semiconductor. We found that electrodes with optimal CuWO 4 thickness exhibit visible light activity due to the absorption of long-wavelength photons and a balanced electron and hole extraction from the oxide. The PEC performance of CuWO 4 is light-intensity-dependent, with charge recombination increasing with light intensity and most photogenerated charge carriers recombining in bulk sites, as demonstrated by PEC tests performed in the presence of sacrificial agents or cocatalysts. The best-performing 580 nm thick CuWO 4 electrode delivers a photocurrent of 0.37 mA cm −2 at 1.23 V SHE , with a 7% absorbed photon to current efficiency over the CuWO 4 absorption spectrum.
“…This value is in line with previous records for CuWO 4 -based electrodes prepared with different synthetic strategies ( Table 2 ). 41 , 42 However, it is far from the maximum photocurrent expected for the 2.2 eV band gap of CuWO 4 . Indeed, assuming that all absorbed photons in the CuWO 4 :580 electrode ( Figure 2 D) are completely converted into current would lead to a 5.6 mA cm –2 theoretical maximum photoresponse under 1 sun illumination.…”
CuWO 4 is a ternary semiconductor oxide with excellent visible light harvesting properties up to 550 nm and stability at high pH values, which make it a suitable material to build photoanodes for solar light conversion to hydrogen via water splitting. In this work, we studied the photoelectrochemical (PEC) performance of transparent CuWO 4 electrodes with tunable light absorption and thickness, aiming at identifying the intrinsic bottlenecks of photogenerated charge carriers in this semiconductor. We found that electrodes with optimal CuWO 4 thickness exhibit visible light activity due to the absorption of long-wavelength photons and a balanced electron and hole extraction from the oxide. The PEC performance of CuWO 4 is light-intensity-dependent, with charge recombination increasing with light intensity and most photogenerated charge carriers recombining in bulk sites, as demonstrated by PEC tests performed in the presence of sacrificial agents or cocatalysts. The best-performing 580 nm thick CuWO 4 electrode delivers a photocurrent of 0.37 mA cm −2 at 1.23 V SHE , with a 7% absorbed photon to current efficiency over the CuWO 4 absorption spectrum.
“…The NiWO 4 has a distorted wolframite crystal structure similar to CuWO 4 and can form a type II heterojunction with CuWO 4 due to its higher energy CB and VB levels than those of CuWO 4 , reducing electron-hole recombination and improving IPCE [56]. P. Shadabipour et al [57] deposited a well-known Ni-and Fe-based co-catalyst on CuWO 4 , but the OER efficiency of Ni 0.75 Fe 0.25 O y /CuWO 4 did not significantly increase because photoexcited holes did not migrate efficiently and the reaction occurred preferentially on the CuWO 4 surface rather than on the co-catalyst.…”
Section: Surface Modification Via Co-catalyst Loadingmentioning
Solar fuel production using a photoelectrochemical (PEC) cell is considered as an effective solution to address the climate change caused by CO2 emissions, as well as the ever-growing global demand for energy. Like all other solar energy utilization technologies, the PEC cell requires a light absorber that can efficiently convert photons into charge carriers, which are eventually converted into chemical energy. The light absorber used as a photoelectrode determines the most important factors for PEC technology—efficiency, stability, and the cost of the system. Despite intensive research in the last two decades, there is no ideal material that satisfies all these criteria to the level that makes this technology practical. Thus, further exploration and development of the photoelectode materials are necessary, especially by finding a new promising semiconductor material with a suitable band gap and photoelectronic properties. CuWO4 (n-type, Eg = 2.3 eV) is one of those emerging materials that has favorable intrinsic properties for photo(electro)catalytic water oxidation, yet it has been receiving less attention than it deserves. Nonetheless, valuable pioneering studies have been reported for this material, proving its potential to become a significant option as a photoanode material for PEC cells. Herein, we review recent progress of CuWO4-based photoelectrodes; discuss the material’s optoelectronic properties, synthesis methods, and PEC characteristics; and finally provide perspective of its applications as a photoelectrode for PEC solar fuel production.
“…Among them, CuWO 4 is one of the most encouraging materials as photoanode owing to its reasonable narrow band gap (2.3 eV), and a maximum theoretical photocurrent density up to ∼9 mA cm −2 can be expected, similarly to the best-performing oxide photoanode candidate BiVO 4 [13]. Nevertheless, CuWO 4 manifest relatively low PEC performance and decorating CuWO 4 with most electrocatalysts has not shown for promoting the water oxidation efficiency unlike nearly all other photoanodes [14][15][16]. For example, an optimized oriented CuWO 4 film with a high exposure ratio of the (100) crystal facet presented a photocurrent density of 0.38 mA cm −2 under 1 sun illumination at +1.23 V versus the reversible hydrogen electrode (RHE) [17].…”
Ternary-phase CuWO4 oxide with an electronic band gap of 2.2–2.4 eV is a potential candidate photoanode material for photoelectrochemical (PEC) water splitting. Herein, we present an efficient method to prepare CuWO4 film photoanode by combining hydrothermal method and hybrid microwave annealing (HMA) process. In comparison with conventional thermal annealing (CTA), HMA can achieve CuWO4 thin film within minutes by using SiC susceptor. When the CuWO4 photoanode is prepared by HMA, its PEC water oxidation performance improves from 0.21 to 0.29 mA cm−2 at 1.23 VRHE comparing with the one prepared by CTA. The origin of the enhanced photocurrent was investigated by means of complementary physical characterizations and PEC methods. The results demonstrated that the obtained HMA processed CuWO4 photoanode not only exhibited intrinsic porous nanostructures but also abundant surface hydroxyl groups, which facilitated sufficient mass transport and the charge transfer. Our results highlight the application of HMA for the fast fabrication of porous film photo-electrodes without using sacrificial template.
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