4.1 Materials
K4[Fe(CN)6],
K3[Fe(CN)6], lithium bromide,
pyrogallic acid,
polyethyleneimine (MW: 70 000,
50% wt/v aqueous solution) and sodium carboxymethylcellulose
(600-1000mpa, USP) were purchased from Macklin (Shanghai, China).
Acrylamide monomer, ammonium persulfate and N,N′-methylene bisacrylamide
were purchased from Aladdin (Shanghai, China). Carbon nanotubes were
purchased from XFNANO (Nanjing, China).
4.2 Preparation of PA-PEI-Fe film
Pyrogallic acid (1.5 g) was added to a stirred solution of
polyethyleneimine (20 g) in deionized water (100 mL) under an atmosphere
of nitrogen. A pre-prepared solution of
K4[Fe(CN)6]/K3[Fe(CN)6]
(0.1 M) and lithium bromide (10 ml, 5.4 mol L−1) was
then added to the resulting brown solution and the two were mixed
thoroughly. Finally, the mixture was poured into a square mold and
spread into a thin film.
4.3 Preparation of TEH
48 ml of the hydrogel prepolymerization solution contained 7.2 g of
acrylamide, 36 mg of ammonium persulfate and 4.8 mg of N, N-methylene
bisacrylamide. The hydrogel prepolymerization solution was poured into a
mold and heated to 60°C for 30 min to polymerization. Then, place the
hydrogel into a mixed solution with
K4[Fe(CN)6]/K3[Fe(CN)6]
(0.1 M) and lithium bromide (5.4 mol L−1) for 3 days
to allow adsorption and formation of TEH.
4.4 Preparation of TEH-CNT
Carbon nanotubes were applied as a photothermal layer on the top surface
of the thermoelectric hydrogel (TEH). To establish electrical
connectivity, a conductive carbon cloth (8 × 65 mm) was used to connect
the upper and lower surfaces of the hydrogel, serving as electrodes. To
ensure the device’s integrity, the solar-driven TEH-CNT device was
sealed using a DELI vacuum machine and thermoplastic tape.
4.5 Preparation of PTEH-Interlocking
TEH was soaked in PA solution (pyrogallol, 12.6 mg
mL−1, polyethyleneimine, 0.2g mL−1)
for 10 min, removed and wiped free of residual PA solution. The upper
and lower surfaces of the hydrogel were subsequently connected using a
conductive carbon cloth (8 × 65 mm) as electrodes. Finally, the
solar-driven PTEH-Interlocking was hermetically sealed by a DELI vacuum
machine with thermoplastic tape.