Efficient solar steam generation and concurrent salt harvesting from saline water were achieved with both continuous operation and long-term stability.

The synthesis of hydrogen peroxide (H2O2) from H2O and O2 by metal-free photocatalysts (e.g., graphitic carbon nitride, C3N4) is a potentially promising approach to generate H2O2. However, the photocatalytic H2O2 generation activity of the pristine C3N4 in pure H2O is poor due to unpropitious rapid charge recombination and unfavorable selectivity. Herein, we report a facile method to boost the photocatalytic H2O2 production by grafting cationic polyethylenimine (PEI) molecules onto C3N4. Experimental results and density functional theory (DFT) calculations demonstrate PEI can tune the local electronic environment of C3N4. The unique intermolecular electronic interaction in PEI/C3N4 not only improves the electron–hole separation but also promotes the two-electron O2 reduction to H2O2 via the sequential two-step single-electron reduction route. With the synergy of improved charge separation and high selectivity of two-electron O2 reduction, PEI/C3N4 exhibits an unexpectedly high H2O2 generation activity of 208.1 μmol g–1 h–1, which is 25-fold higher than that of pristine C3N4. This study establishes a paradigm of tuning the electronic property of C3N4 via functional molecules for boosted photocatalysis activity and selectivity.

energy storage and conversion devices, [26][27][28] as outlined in recent reviews (Figure 1, left). [29] Behind these applications lie a fundamental question: how water and ion transport are controlled in the laminar structure to obtain desired selectivity. A comprehensive summary of structure-transport relation is thereby imperative to understand and optimize membrane selective performance, but is so far lacking. In such context, our review aims to fill this gap by discussing: 1) how 2D materials with specific physicochemical features are assembled into laminar membranes; 2) most importantly, how membrane structure, and its response to external impacts, can tune mass transport (herein, water and ions); 3) how these transport mechanisms translate into selectivity in applications, and into future design of high-performance laminar membranes. Unsolved problems and emerging challenges around these topics are then concluded. We note that the knowledge summarized here can also, at least partly, assist the understanding of the selective gas, liquid, and micromolecule transport through laminar membranes, which are gaining considerable attention as well. [30][31][32] Transition Metal Carbides and/or Nitrides (MXene): MXene nanosheets are etched and delaminated from parent bulk MAX to M n+1 X n T x (e.g., Ti 3 C 2 T x ), and have thus several atom sublayers. [39] While M and X are early transition metal