Biomass-derived carbons for supercapacitors provide a promising and sustainable strategy to address the worldwide energy and climate change challenges. Here, we have designed and constructed three-dimensional nitrogen/sulfur-codoped hierarchically porous carbons for high-performance supercapacitor electrode materials in a one-step process, in which ginkgo leaf is used as a carbon source and S source and ammonium nitrate (AN) is used as an activating agent and a N source. During the synchronous carbonization and activation process, AN could be decomposed completely into gaseous byproducts and be removed easily without leaving residues after product formation. The as-synthesized ginkgo leaf-derived carbons exhibited a high specific capacitance of 330.5 F g –1 at a current density of 0.5 A g –1 and a capacitance of 252 F g –1 even at a high current density of 10 A g –1 with an excellent capacitance retention of 85.8% after 10 000 cycles in 6 mol L –1 KOH electrolyte. The present study provides an efficient, sustainable, and facile approach to prepare renewable hierarchically porous carbons as advanced electrode materials for energy storage and conversion.

Electrochemical water splitting into H 2 and O 2 provides a promising and sustainable strategy for the future production of clean energy. Herein, we report an ammonium nitrate (AN)assisted synthetic strategy to prepare Co, Co 2 P@CoP nanoparticles embedded in biomass-derived porous carbons as bifunctional electrodes for water splitting. The use of AN is not only activating biomass to porous carbons, but also reducing the synthetic temperature significantly. The synergistic effects of the Co 2 P@CoP heterostructure could lead to a low adsorption energy of hydrogen (ΔG H*) and conduction band bending, together with the N/S-codoped porous carbons could provide large specific surface area and desirable electrondonating feature, contribute to the remarkable performance with overpotentials of 0.129 and 0.212 V for hydrogen evolution reaction (HER) in 0.5 mol L À 1 H 2 SO 4 and 1 mol L À 1 KOH, and 0.328 V for oxygen evolution reaction (OER) in 1 mol L À 1 KOH, at a current density of 10 mA cm À 2. Moreover, the Co 2 P@CoP/PC catalysts enable overall water splitting with a small cell voltage of 1.63 V to achieve 10 mA cm À 2 and exhibit long-term durability over 1000 min.

The photocatalytic activities of as-synthesized Ag/AgBr/GO nanocomposites became weaker when alkyl chain became shorter, whereas an opposite change for their SERS enhancements.

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