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[Display omitted] • N-doped 3D hierarchical porous carbons (3DNHPCs) are prepared in a green strategy. • Tertiary porous structure and surface-exposed active sites accelerate ion insertion. • Superior desalination capacity and rapid desalination rate are achieved. • Ultrahigh water recovery and productivity are acquired. Exploiting a sustainable and effective strategy for fabricating 3D N-doped hierarchical porous carbon (3DNHPC) for capacitive deionization (CDI) is a huge challenge for desalination. The traditional methods often adopt expensive precursors, complex routes and strong corrosive activators that are harmful for its practical application. Herein, a novel green double organic salt activation strategy is developed that utilizes lotus stem (LS) with a regular 3D macroarray structure to acquire 3DNHPC x. Different from single C 6 H 5 K 3 O 7 or Na 2 EDTA activation, 3DNHPC x obtained under double organic salt co-activation exhibits a suitable micro-meso-macro porous structure with a high BET surface area (S BET) of 2256.2 m2/g, a large pore volume of 1.02 cm3/g, a remarkable mesoporous volume of 0.41 cm3/g and 1.31 % N content. Its unique tertiary pore structure and copious surface-exposed active sites facilitate the ions rapid insertion and extraction from the micropores. The assembled CDI cells achieve a superior salt removal capability of 25.36 mg/g as well as a splendid volumetric adsorption capacity (VAC) of 6.21 mg/cm3 and an ultrafast average salt removal rate of 7.84 mg/g/min. Meanwhile, 3DNHPC 11 maintain 89.4 % adsorption capacity after 50 cycles. Besides, 3DNHPC 11 obtains a high water recovery (WR) of 82.2 % and high productivity of 290 g NaCl /g C /(h m2) or 108.1 g NaCl /cm3 C /(h m2). This work sheds light on one way to design economical and eco-friendly 3DNHPCs for high-performance CDI desalination. [ABSTRACT FROM AUTHOR]

[Display omitted] • Nitrate-mediated organic salt activation strategy was proposed to fabricate high-yield-high-performance NHPC. • Tertiary porous structure and surface-exposed active sites facilitated salt ion removal. • The splendid desalination capability and rapid desalination kinetics were acquired. • The universality and commerciality for NHPCX y were further investigated. Developing a green and facile strategy for high-yield preparing N-doped hierarchical porous carbon (NHPC) for capacitive deionization (CDI) is a huge challenge for desalination. So far, there are limited reports on high-yield NHPC synthesis. Herein, a novel nitrate (NaNO 3 , KNO 3 , Zn(NO 3) 2 and NH 4 NO 3)-mediated-organic salt activation strategy was exploited to construct NHPCX y (X = Na, K, Zn, NH 4 ; Y(nitrate ratio) = 1, 3, 5). Thereinto, C 6 H 5 K 3 O 7 served as activator and nitrate acted as assisted-activator and foaming agent. Compared with C 6 H 5 K 3 O 7 activation, NHPCNa 3 acquired by NaNO 3 -C 6 H 5 K 3 O 7 co-activation achieved 35.5% high yield and depicted 3D macroarray structures with high specific surface area (S BET) of 1912.2 m2/g, large pore volume (V pore) of 1.56 cm3/g and 1.21 % N content. Its tertiary pore structure and rich surface-exposed active sites favored the ions rapid insertion and extraction from the micropores. The final NHPCNa 3 delivered an excellent salt adsorption capacity (SAC) of 19.74 mg/g. Moreover, it exhibited 14.61 mg/g high SAC at 15.5 mg/cm2 and only showed 9.4% SAC drop after 50 cycles. While using diverse biomass precursors, it obtained an optimal SAC of 23.16 mg/g. NHPCK 3 , NHPCZn 3 and NHPC(NH 4) 3 also presented the feature of high-yield-high-performance. The high yield came from the foaming effect of nitrate and the property difference may be ascribed to the different cations. This work provides one span-new green universality strategy to design high-yield-high-performance NHPCs in commercial-grade CDI applications. [ABSTRACT FROM AUTHOR]

[Display omitted] • The universal low carbon mass loading was used in capacitive deionization (CDI) for efficient deionized (DI) water production. • Partial desalination performance weakened with increasing carbon mass loading. • CDI cells using YEC-8–5.81 as electrodes produced DI water with a low conductivity of 1.89 μS/cm. • Carbons with a suitable micro- meso pore distribution and high specific capacitance may be a better choice. • 82.2% DI water recovery was achieved under stopped flow (SF) discharge mode. High-purity deionized (DI) water can be widely used in high-end manufacturing fields, but its efficient and energy-saving production is a huge challenge. Here, simple carbon mass loading control was developed for efficient DI water production via advanced capacitive deionization (CDI). Supercapacitor carbon (YEC-8) electrodes with diverse mass loading of 2.50, 5.81, 12.63 and 24.72 mg/cm2 were prepared for desalination. As expected, YEC-8–2.50 acquired the optimal CDI performance. High mass loading of 12.63 and 24.72 mg/cm2 not only caused an overt property drop but also serious wasted materials. Competitively, YEC-8–5.81 achieved a similar volumetric adsorption capacity (VAC) to YEC-8–2.50 as well as made up for the lack of total mass of YEC-8–2.50 and the resultant solution conductivity was as low as 1.89 μS/cm (grade III DI water). This strategy has been successfully extended to other carbon materials and carbons with suitable micro- meso pore distribution and high specific capacitance may be a better choice. Besides, the reverse effect of acetylene black (AB) mass on desalination was verified. To gain a high water recovery (W R), stopped flow (SF) discharge was introduced and realized a high W R of 82.2 %. Meanwhile, cycling tests indicated its splendid cycling stability. This study provides a universal direction for using low mass loading strategy for efficient DI water production. [ABSTRACT FROM AUTHOR]