Syntheses, characterizationsna and water-electrolysis properties of 2D α- and β-PdSeO3 bulk and nanosheet semiconductors

In contrast to alkaline water electrolysis, water electrolysis in an acidic environment has higher energy efficiency, more compact cell design, higher gas purity, and less sensitivity to environmental impurity. Herein, the syntheses of the known 2D α- and β-PdSeO3 were improved. The bulk materials were exfoliated into nanosheets using an ultrasonic-assisted liquid-phase exfoliation similar to that of preparing graphene nanosheets. Their band-gaps, valence band maximums (VBMs) and conduction band minimums (CBMs) were determined using Mott-Schottky plots and the linear potential scan method in acidic aqueous solution, 0.2 ​M Na2SO4 aqueous solution and non-aqueous solution. Their transient photocurrent properties were also examined, along with their Electrochemical Impedance Spectra (EIS). The bulk materials are stable in pH ​= ​0–14 value water solution for at least 48 ​h. α- and β-PdSeO3 nanosheets exhibit moderate catalytic activities for hydrogen evolution reactions in 0.5 ​M ​H2SO4 (η10 (overpotential at 10 ​mA ​cm-2: 185 and 209 ​mV, respectively; catalyst loading: 0.28 ​mg ​cm-2), much better than the performances of the bulk materials. In addition, β-PdSeO3 bulk and nanosheets materials show good and similar OER catalytic activities in 0.5 ​M ​H2SO4 (η10: 381 and 405 ​mV, respectively; catalyst loading: 0.28 ​mg ​cm-2). Thus, β-PdSeO3 nanosheets were found to be a good overall water splitting catalyst in acidic solution. The above catalysts all show long-term stability. In contrast, α-PdSeO3 does not have OER catalytic property. To our knowledge, Pd-based acidic overall water splitting catalysts are very rare.