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• The loading of CNT into acid-treated carbon papers enhances the 2e-transfer process. • The Faradaic efficiency for H 2 O 2 production using CNT/a-CP cathodes is ˜100. • The Faradaic efficiency for As(III) oxidation using h-TNR photoanodes is >80%. • The h-TNR and CNT/a-CP pair drives the As(III) oxidation and H 2 O 2 production. We present an off-grid, standalone electrocatalytic H 2 O 2 production reaction (HPR) using carbon nanotubes (CNT) wired to hydrogen-treated TiO 2 nanorod (h-TNR) arrays catalyzing the oxidation of As(III) to As(V) under simulated solar light (AM 1.5; 100 mW cm−2). Loading CNT onto acid-treated carbon paper (a-CP) significantly enhances the catalytic 2-electron transfer to O 2 , leading to a Faradaic efficiency (FE) of ∼100% for the HPR. To drive the HPR, the 2-electron oxidation of toxic As(III) to less toxic As(V) that accompanies the production of the proton/electron couples is achieved at an FE of >80% using the h-TNR arrays. The high FEs of the anodic and cathodic reactions are maintained over 10 h when a direct-current voltage of 0.7 V is applied to the h-TNR photoanode and CNT/a-CP cathode pair. The coupling of a mono-Si photovoltaic array that is one-tenth the size of h-TNR photoanode to the pair of h-TNR and CNT/a-CP successfully drives the standalone operation of both reactions at the high FEs (>90%). The surface characterization of the as-synthesized materials and the reaction mechanism are discussed in detail. [ABSTRACT FROM AUTHOR]

A hetero-tandem organic photovoltaic (OPV) device consisting of large (PM6:IT-M) and small-bandgap (PM6:Y6) bulk-heterojunctions is developed to provide an open-circuit voltage of 1.84 V and a power-conversion-efficiency of 11.7%, which could serve as an ideal light absorber to drive water electrolysis. The fabricated OPV is combined with an electrolyzer composed of NiFeO x (OH) y and Pt electrocatalysts to demonstrate a photovoltaic-electrolysis (PV-EC) system. Furthermore, the system is designed to locate the operating voltage of the OPV-EC system at the maximum power point of OPV to minimize power loss. As a result, our hetero-tandem OPV-EC device achieves the highest solar-to-hydrogen conversion efficiency among OPV-based systems, (up to 10%), which represents a new benchmark for OPV-based solar fuel production. Finally, a wireless monolithic organic-artificial leaf is constructed for the first time, which demonstrates a stable solar hydrogen production in water. [Display omitted] • A unique hetero tandem organic photovoltaic (OPV) was fabricated consisting of two different bandgap materials. • Solar-driven water splitting system combining OPV and alkaline water electrolysis cell (EC) was fabricated. • New benchmark of STH efficiency (10%) and electricity-to-hydrogen efficiency (84.5%) were achieved. • Wireless stand-alone organic artificial leaf was implemented utilizing the same configuration. [ABSTRACT FROM AUTHOR]

In this study, we demonstrated high-rate H 2 generation by coupling with the sulfite oxidation reaction (SOR) as an alternative to the oxygen evolution reaction for solar H 2 production. The emerging and cost-effective molybdenum phosphide electrocatalyst was appropriately optimized and used as a bifunctional catalyst in an alkaline electrolyte for both SOR and HER. Powered by state-of-the-art perovskite–Si tandem photovoltaics, a remarkable photocurrent density of over 17 mA cm−2 was achieved in the HER coupled with the SOR. In addition to the significantly enhanced photocurrent, the SOR can further reduce the overall cost of solar H 2 production owing to the elimination of the expensive membranes required for H 2 and O 2 gas separation. Considering the high global demand for desulfurization via the SOR, the strategy proposed here will enable practical H 2 production from renewable sources while effectively converting the toxic SO 2 gas into a value-added product for the chemical industry. Solar hydrogen production system employing SOR as alternative anodic reaction is presented. Photoassisted electrochemical device consists of MoP-based catalysts and perovskite–Si tandem PV. Our system based on SOR demonstrates remarkable hydrogen generation photocurrent density of over 17 mA cm–2 under 1-sun illumination with prolonged durability of 50 h. [Display omitted] • Solar H 2 production employing SOR as an alternative anodic reaction is presented. • SOR enables the reduction in thermodynamic barrier for H 2 production. • Bifunctional MoP-based catalysts for SOR–HER is developed. • SOR-based PV-EC exhibits photocurrent of 17.23 mA cm–2 with durability of 50 h. [ABSTRACT FROM AUTHOR]

[Display omitted] • The synergistic structure with nanoporous BiVO 4 and SnO 2 nanorods boosting the photoelectrochemical properties. • Near-complete charge separation efficiency of 97% and charge carrier dynamics of BiVO 4 /SnO 2. • Spontaneous water oxidation with STH conversion efficiency of 7.3% implemented by the PEC-PV tandem cell. As an artificial leaf, a tandem device for zero-bias solar water splitting is a capable solution for practical hydrogen production. Despite a promise, poor charge transport of BiVO 4 hampers photoelectrochemical performances under front-side illumination, which is a hindrance to the tandem system. Herein, we design a new photoanode comprising nanoporous BiVO 4 and SnO 2 nanorods focused on the charge separation via structural and interfacial engineering. BiVO 4 /SnO 2 photoanode exhibits not only remarkable charge separation efficiency of 97% but also, by loading NiFe as a co-catalyst for water oxidation, high photocurrent density of 5.61 mA cm−2 at 1.23 V versus the reversible hydrogen electrode under front-side 1 sun illumination. Consequently, a tandem cell comprising NiFe/BiVO 4 /SnO 2 photoanode and perovskite/Si tandem solar cell generates an operating photocurrent density of 5.90 mA cm−2 with a solar-to-hydrogen conversion efficiency of 7.3% in zero-bias. This work would be a significant step to develop spontaneous solar hydrogen production. [ABSTRACT FROM AUTHOR]