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Exploring highly efficient single atom catalysts with defined active centers and tunable electronic structures is highly desirable. Herein, we developed an efficient hydrogen evolution reaction (HER) electrocatalyst through a self-gating phenomenon induced by Pt single atoms (SAs) supported on ultrathin NiO nanosheets (Pt SA -NiO). The Ni atoms in NiO are partially replaced by the atomically dispersed Pt atoms, leading to a transition from p-type NiO into n-type Pt SA -NiO. When the n-type Pt SA -NiO serves as HER electrocatalyst, the self-gating phenomenon occurs in the ultrathin nanosheets, resulting in a mixture of leakage ("active") and metal-insulator-semiconductor ("inert") regions. The "inert" region induced by the ionic gating and reverse potential is capable of accumulating relatively high surface charge carrier concentration with an ultrahigh electric field, making the Pt SA -NiO highly conductive; meanwhile, the HER process occurs at the Pt SAs sites (active region) in the Pt SA -NiO nanosheets. As a result, the Pt SA -NiO requires only 55 mV to deliver 10 mA/cm 2 in an alkaline solution with good stability.

Zinc-nickel batteries are promising competitors for next-generation power supply due to their benefits of high safety, high working voltage, and attractive rate performance. However, their practical applications are plagued by their poor cycling performance, stemming from uneven redistribution of zinc during cycling that results in dendrite formation and shape changes of the electrode. In this work, mesoporous Ti 4 O 7 microspheres are prepared and are employed as additives of a zinc anode. Notably, the presence of mesopores provides abundant chemisorption sites for Zn(OH) 4 2- ions, inhibiting severe zinc redistribution in the electrode. Moreover, due to the good electrical conductivity and mesopores that serve as ion diffusion channels, the reaction reactivity and reversibility of the zinc electrode are greatly facilitated. As a result, the fabricated zinc-nickel battery with mesoporous Ti 4 O 7 additives (ms-Ti 4 O 7 ) exhibits an enhanced discharge capacity and a significantly prolonged cycling life. Even at a current of 10 A (∼138 mA cm -2 ), the ms-Ti 4 O 7 -modified anode demonstrates stable operation for longer than 718 h (700 cycles) with a discharge voltage of 1.2 V, which is much longer than those of a ZnO anode (192 h, 117 cycles) and a Ti 4 O 7 -particle (p-Ti 4 O 7 )-modified battery (590 h, 443 cycles). Furthermore, due to the anchoring effect for Zn(OH) 4 2- and the uniform electric field, the effect of mesoporous Ti 4 O 7 on inhibiting dendrite formation and shape change of the zinc electrode is highlighted.

Converting CO 2 into value-added chemicals and fuels is one of the promising approaches to alleviate CO 2 emissions, reduce the dependence on nonrenewable energy resources, and minimize the negative environmental effect of fossil fuels. This work used density functional theory (DFT) calculations combined with microkinetic modeling to provide fundamental insight into the mechanisms of CO 2 hydrogenation to hydrocarbons over the iron carbide catalyst, with a focus on understanding the energetically favorable pathways and kinetic controlling factors for selective hydrocarbon production. The crystal orbital Hamiltonian population analysis demonstrated that the transition states associated with O-H bond formation steps within the path are less stable than those of C-H bond formation, accounting for the observed higher barriers in O-H bond formation from DFT. Energetically favorable pathways for CO 2 hydrogenation to CH 4 and C 2 H 4 products were identified which go through an HCOO intermediate, while the CH* species was found to be the key C 1 intermediate over χ-Fe 5 C 2 (510). The microkinetic modeling results showed that the relative selectivity to CH 4 is higher than C 2 H 4 in CO 2 hydrogenation, but the trend is opposite under CO hydrogenation conditions. The major impact on C 2 hydrocarbon production is attributed to the high surface coverage of O* from CO 2 conversion, which occupies crucial active sites and impedes C-C couplings to C 2 species over χ-Fe 5 C 2 (510). The coexistence of iron oxide and carbide phases was proposed and the interfacial sites created between the two phases impact CO 2 surface chemistry. Adding potassium into the Fe 5 C 2 catalyst accelerates O* removal from the carbide surface, enhances the stability of the iron carbide catalyst, thus, promotes C-C couplings to hydrocarbons.

Acid recycling and arsenic recovery from strongly acidic wastewater are goals of the metallurgical industry to reduce carbon emissions. In this study, arsenic was recovered using a hydroxyl-enriched CeO 2 adsorbent, and the adsorption mechanism in a strongly acidic solution was investigated. The adsorption capacities of 88.59 mg/g for As(III) and 126.211 mg/g for As(V) at pH 1.0 are the highest reported values to date. It is revealed that the hydroxyl groups on the CeO 2 surface can buffer hydrogen ions, and the isoelectric point of the material can be reduced to pH 1.52. The binding energy of arsenic is -1.25 eV for the hydroxyl-enriched CeO 2 and -2.24 eV for CeO 2 without hydroxyl groups. Additionally, the protonated hydroxyl groups reduce the oxidation energy of As(III) and promote the adsorption of arsenic by forming new active sites in the strongly acidic solution. Nearly 98.11% of arsenic (initial concentration is 886.8 mg/L) is removed within 24 h without pH adjustment, indicating the feasibility of hydroxyl-enriched CeO 2 for recovering arsenic and acid. This work investigated the adsorption and proton-enhanced oxidation mechanism of arsenic by hydroxyl-enriched CeO 2 in strongly acidic wastewater.

Facilitating the efficient activation of N 2 molecules and inhibiting the competing hydrogen evolution reaction remain a challenge in the nitrogen reduction reaction (NRR). A heteroatom doping strategy is an effective way to optimize the energy barrier during the NRR process to improve the catalytic efficiency. Herein, we report Ni-doped Mo 2 C anchored on graphitized porous conductive carbon for regulating the electronic structure and catalytic properties of electrocatalysts toward NRR. Benefiting from the porous structure and graphitization features of the carbon matrix, more active sites and high electronic conductivity were achieved. Meanwhile, with the doping of Ni atoms, the electronic configuration near the Ni-Mo active sites was optimized and the adsorption of N 2 on them was also promoted due to the increased electron transfer. Moreover, the lowered energy barrier of the NRR process and the suppressed hydrogen adsorption on the active site all resulted in the high catalytic activity and selectivity of the catalyst. Therefore, a high NH 3 yield rate of 46.49 μg h -1 mg -1 and a faradic efficiency of 29.05% were achieved. This work not only validates the important role of heteroatom doping on the regulation of NRR catalytic activity but also provides a promising avenue for the green synthesis of NH 3 .