Copper-surface-mediated synthesis of acetylenic carbon-rich nanofibers for active metal-free photocathodes

Abstract

The engineering of acetylenic carbon-rich nanostructures has great potential in many applications, such as nanoelectronics, chemical sensors, energy storage, and conversion, etc. Here we show the synthesis of acetylenic carbon-rich nanofibers via copper-surface-mediated Glaser polycondensation of 1,3,5-triethynylbenzene on a variety of conducting (e.g., copper, graphite, fluorine-doped tin oxide, and titanium) and non-conducting (e.g., Kapton, glass, and silicon dioxide) substrates. The obtained nanofibers (with optical bandgap of 2.51 eV) exhibit photocatalytic activity in photoelectrochemical cells, yielding saturated cathodic photocurrent of ca. 10 µA cm−2 (0.3–0 V vs. reversible hydrogen electrode). By incorporating thieno[3,2-b]thiophene units into the nanofibers, a redshift (ca. 100 nm) of light absorption edge and twofold of the photocurrent are achieved, rivalling those of state-of-the-art metal-free photocathodes (e.g., graphitic carbon nitride of 0.1–1 µA cm−2). This work highlights the promise of utilizing acetylenic carbon-rich materials as efficient and sustainable photocathodes for water reduction

Interfacial Approach toward Benzene‐Bridged Polypyrrole Film–Based Micro‐Supercapacitors with Ultrahigh Volumetric Power Density

“…Furthermore, the optical bandgap could be calculated from the absorption edge of the ultraviolet–visible absorption spectrum (Figure S11, Supporting Information) . A Tauc plot reveals a bandgap of ≈2.0 eV (Figure b,c) . In addition, the cyclic voltammetry (CV) of PbPPy film deposited on the glassy carbon was measured in argon‐saturated acetonitrile (Figure S12, Supporting Information).…”

Molecular Engineering of Conjugated Acetylenic Polymers for Efficient Cocatalyst‐free Photoelectrochemical Water Reduction

“…Therefore, besides serving as a conductive substrate, the Cu foam simultaneously functioned as a catalyst. The C≡C coupling of DET occurred at the Cu‐liquid interface where various Cu species (Cu I and Cu II triggered by piperidine) were released, yielding a pDET film deposited directly on the Cu foam surface (Supporting Information, Figure S2) . In order to determine the growth process of pDET, the products were investigated at several reaction stages (Figure b,c and Supporting Information, Figure S3–5).…”

“…As disclosed in Figure S10 in the Supporting Information, the Raman peaks at 2200 and 2185 cm −1 originate from the C≡C bonds in pDEB and pDEN, respectively. However, the characteristic signals of C≡C bonds in the pDTT and pDET negatively shift to 2158 and 2165 cm −1 , respectively . For high‐resolution X‐ray photoelectron spectra of C 1s, the sp‐carbon peaks of pDEB and pDEN appear at 284.2 and 283.8 eV, while the sp‐carbon signals of pDTT and pDET appear at 283.7 and 283.6 eV, respectively (Supporting Information, Figures S11–15).…”

“…This value is significantly higher than IPCE values at 520 nm of all reported organic photocathodes, for example C 3 N 4 (approximately 0.2–0.3 %), BDT‐ETTA COFs (approximately 0.05 %), and many inorganic photocathodes, including Cu 2 O (approximately 10.0 %), NiO (approximately 1.5 %), and WSe 2 (approximately 0.2 %) (Figure d). To clarify the effect of the surface area of the Cu foam, we also measured the photocurrents generated from poly(1,3,5‐triethynylbenzene) (pTEB) reported in our previous work on different Cu substrates (Supporting Information, Figure S27). Compared with the pTEB on Cu foil (approximately 15 μA cm −2 at 0.3 V vs. RHE), the pTEB on Cu foam delivered approximately 2.7 times higher photocurrent (approximately 40 μA cm −2 at 0.3 V vs. RHE), which is nearly one tenth of that of pDET/Cu.…”

“…According to their absorption and IPCE spectra, two laser lines (594 nm and 647 nm, one close and one far below the optical band gap) were used to record the Raman spectra of thiophene‐based pDET as a function of applied potential (Figure and Supporting Information, Figures S45 and S46). In the characteristic vibration region of C≡C bonds (1850–2250 cm −1 ) of pDET and pDTT, no potential‐dependent variations were observed in the differential Raman spectra upon laser excitation at 647 nm (Supporting Information, Figure S44). These results are consistent with the absence of synchronously recorded photocurrents (Supporting Information, Figure S44 a) and IPCE results (Figure c and Supporting Information, Figure S26), which show no PEC response under irradiation above 640 nm.…”